Power Supply Adapter

Lithium-ion (Li-ion) Battery Charger with MAX1879

2012-01-23T17:29:00.000-08:00

Above diagram is the circuit of Lithium-ion (Li-ion) battery charger which built based single chip MAX1879. This is the simple and low cost battery charger for single-cell Li+ battery that does not dissipate power (no heat.

The MAX1879, in conjunction with the AC linear transformer adapter and a PMOS FET, allows safe and fast charging of a single Li+ cell. The MAX1879 is not only an inductorless required solution, but also the lowest power dissipated solution among single-cell Li+ battery chargers.

The MAX1879 with a current limited linear wall adapter can produce the most economic and efficient solution for the single-cell Li+ off-line cradle charger, with virtually no power loss on the PMOS FET. It can be easily designed for handheld devices or battery packs without excessive power dissipation and heat problems.

Read detailed explanation about this Lithium-ion (Li-ion) battery charger circuit at maxim-ic.com

About MAX1879:
The MAX1879 single-cell lithium-ion (Li+) battery charger utilizes an efficient pulse-charging architecture to minimize power dissipation in portable devices. This architecture combines the efficiency of switch-mode chargers with the low cost and simplicity of linear chargers. This simple device, in conjunction with a current-limited wall cube and a PMOS transistor, allows safe and fast charging of a single Li+ cell.

MAX1879 Features:

Low Electronic Component Count, No Inductor
Simple Design Minimizes Heat
0.75% Accurate Battery Regulation
1.5µA (max) Battery Current Drain with Wall Cube Removed
Restart Charging at 4.0V
Battery-Full Indicator
Safely Precharges Near-Dead Cells
Automatic Power-Down when Power Source is Removed
Continuous Overvoltage and Overtemperature Protection
Charges 1 Cell from as Low as 4.5V
Pin-Compatible Upgrade to MAX1679

Download MAX1879 datasheet

Solid State Tesla Coil with 555 Timer

2012-01-16T17:16:00.000-08:00

Here the circuit diagram of solid state tesla coil with 555 timer.

Single transistor flyback driver induced a lot of complications on account of it really is operating principle. I received e-mails from those who had been unable to obtain it functional even after they are positive that their flyback and transistor is Okay. Moreover, because it is resonance frequency is determined by each individual a part of the method, any time you seek to draw an arc in the transformer, it alterations substantially in a lot of the circumstances. Simply because the operating frequency is vital for your security criteria, (each for mine and electrical power transistor's), I determined to generate it run on a continuous frequency and developed up yet another easy circuit, attempting to keep within the specified limits in the 555 timer.

Setting the operating frequency with an integrated timer is simple and practical. This schematic is absolutely nothing over the normal astable mode circuit layout having a traditional 555. It calls for only two resistors as well as a capacitor to set frequency (with duty cycle certainly) and a further resistor to ascertain electrical power transistor's base current, which it is possible to uncover it is optimal worth experimentally. I employed 1K for R1, two.2K for R2, and 10nF for C which produced circuit to run practically at 27 kHz theoretically, at %60 higher to %40 minimal duty cycle. You may easily calculate operating parameters in the resistance and capacitor values which has a tiny system that I've written.

Values offered for R1, R2 and C within this circuit diagram would be the ones employed on my prototype. You could possibly transform R1 and use a trimmer as a substitute for R2 to discover an optimum frequency / duty cycle blend to your flyback. By shifting C, you may possess the capacity to use increased or reduced resistor values, but tend not to desire as well minimal resistances (primarily for R1) for to not overload 555.

Energy transistor just isn't significant and any other could be applied so long as it really is qualities are equivalent or greater. Listed below are the technical datas for BD243C for comparison:

Bipolar NPN transistor : BD243C
Casing : TO220
Max. collector current : 6 Amperes
Max. complete energy : 65 Watts, even though situation is at 25 degrees Celsius
Transition frequency : 3 MHz
hFE (current obtain) : 30 at 300mA (minimal value)

PCB layout:

Detailed explanation about this circuit, visit this page: Solid State Tesla Coil with 555 Timer

Simple Power Supply Circuit for Laser

2012-01-09T19:15:00.000-08:00

This is a very simple high voltage power supply circuit for laser device. It is low cost circuit and very easy to built. This power supply can be built with common parts, most of which you probably already have in your junk box. The secret of this circuit is the transformer used. It is a common 9V 1A transformer unit, connected backwards for step up. Please note that some people may have trouble with this supply. This is due to the slight difference in transformers.

Parts List:

R1 = 10 Ohm 10W Or Greater Resistor
R2 = Ballast Resistor, read the notes
D1, D2, D3 = 1N4007 Silicon Diode
C1, C2, C3 = 0.1 uF / 2000V Capacitor
T1 = 9V 1A Transformer
S1 = 115V 2A SPST Switch
MISC = Case, Wire, Binding Posts (for output), Line Cord

Circuit Notes:

T1 is an ordinary 9V 1A transformer connected backwards for step up.
R1 MUST be installed on a LARGE heatsink. A good heatsink is the metal case the power supply is built in.
R2 secures the laser tube from excess current. It should be soldered directly to the anode terminal on the tube. To find R2, start with a 500K 10W resistor and work down until the tube lights and remains stable.
If you have trouble with the tube not starting easily, use a longer anode lead that is wrapped around the tube.
Depending on the transformer you use, the circuit may or may not work. Build at your own risk. Some transformers consist of very few secondary windings which will quickly saturate the core and basically act like a direct short. The more secondary windings (that is, primary in this circuit) the better.

Simple power supply circuit for laser, source page: http://www.aaroncake.net/circuits/lasersup.asp

Regulated Current Booster for Power Supply

2012-01-02T16:11:00.000-08:00

This is the regulated current booster designed to increase the DC current of a power supply.

Even though the 78xx series of voltage regulators are readily available with diverse current outputs, you could increase the obtainable current output with this circuit. A power transistor is utilized to provide additional current for the load the regulator, preserving a continuous voltage. Currents as much as 650mA will flow by way of the regulator, above this value along with the power transistor will start out to conduct, supplying the additional existing for the load. This needs to be on an sufficient heat sink as it is actually most likely to obtain rather hot. Suppose you use a 12V regulator, LM7812. The input voltage must be a number of volts greater to permit for voltage drops. Assume 20 Volts. Lets also assume that the load will draw 5 amps. The power dissipation within the transistor will likely be Vce * Ic or (20-12)*8 = 40 Watt. It may possibly preserve you warm within the Winter, but you might have to have a big heatsink with very good thermal dissipation.

If you would like to enhance the output current using a negative regulator, just like the 79xx series, then the circuit is comparable, but an NPN type power transistor is applied as a substitute.

Variable DC Power Supply 3-24V / 3A

2011-12-26T03:48:00.000-08:00

This is the variable DC power supply circuit. This power supply has regulated output, can be adjusted from 3 to 25 volts and the current output is limited to 2 amps as shown, however it may possibly be improved up to 3 amps or more by applying a smaller current sense resistor (0.3 ohm). Voltage regulation is controlled by 1/2 of a 1558 or 1458 op-amp. The 1458 may be substituted in the circuit, but it is suggested the supply voltage to pin 8 be limited to 30 VDC, which can be achieved by adding a 6.2 volt zener or 5.1 K resistor in series with pin 8. The 2N3055 and 2N3053 transistors need to be attached on proper heatsinks and the current sense resistor must be rated at 3 watts minimum.

The maximum DC supply voltage for the 1458 and 1558 is 36 and 44 respectively. The power transformer ought to be capable of the preferred current while keeping an input voltage at least 4 volts higher than the expected output, but not surpassing the maximum supply voltage of the op-amp under minimal load conditions. The power transformer shown is a center tapped 25.2 volt AC / 2 amp unit that will deliver regulated outputs of 24 volts at 0.7 amps, 15 volts at 2 amps, or 6 volts at 3 amps. The 3 amp output is acquired utilizing the center tap of the transformer with the switch in the 18 volt position. All components/parts should be available at Radio Shack with the exception of the 1558 operational amplifier.

Variable DC power supply 3-24V / 3A circuit source page: www.bowdenshobbycircuits.info

600V Power Supply for QRO HF Amplifiers

2011-12-19T00:40:00.000-08:00

Here the schematic design diagram of 600V power supply for QRO HF amplifiers. Amateur Radio Transmitters working with valves such as 807 or1625 operates properly using a plate voltage in between 600V to 700 Volts. The circuit described below is actually a full wave voltage doubler. The output voltage is twice the input voltage. For 230V AC input the output is going to be close to 600 Volts.

Resister R1 is applied to minimize the initial high voltage and high currents. Capacitor C1, C2, C3 along with coils L1 and L2 form input line filter. The capacitors C4 and C5 protects diodes from high voltage transients on the AC line as well as minimizes inter carrier hum modulation of the R.F picked up by the mains. Capacitors C6 and C7 gives sufficient filtering for the output DC Voltage.

Parts List:

C1, C2, C3 = 0.1 mf 630V
C4, C5 = 0.01 mf 630V
C6, C7 = 100 mf 450V
R1 = 10E 5W Wire Wound
R2, R3 = 220KE 2Watts
D1, D2 = BY127
D3, D4 = BY127
L1, L2 = 12 Turns 18 SWG, Wound over 4 Cm, long Ferrite Rode.

600V power supply for QRO HF amplifiers, circuit source:
http://www.flashwebhost.com/circuit/600_volt_power_supply.php

DC Short Circuit Protection with Electronic Fuse

2011-11-23T13:59:00.001-08:00

Here the diagram of electronic fuse circuit. This circuit will help to protect the load against short circuit for DC circuit application. Relays should be chosen with a voltage value equals to the input voltage. Do not omit making use of the 100uF capacitor with proper voltage value with respect to the input voltage. The circuit use Silicon Controlled Rectifier (SCR) BRX46 which is designed for control systems and sensing circuit applications. In case you cannot find this component, it is possible to use C106 as a substitute of BRX46.

It is possible to alter the electric current with applying 10K potentiometer. In the event you will utilize the fuse with very high currents, then reduce the 0R6 5W resistor value (ex. 0R47, 0R33, 0R22 or 0R1). Watt value of the resistor also needs to be increased also.

Discharge Indicator Circuit for 12V Lead Acid Battery

2011-11-12T03:25:00.001-08:00

Here the discharge indicator circuit for Lead Acid battery 12V. This circuit is used to prevent the batteries from damage. When discharging the battery voltage pin 12V Lead may not be reduced below 10.8V, so we notice the lighting of Led, when the voltage falls below this value. To achieve control we need a constant voltage and a circuit that can compare this with the controlled voltage. And these two conditions to ensure the IC1-LM 723.

The input terminals of the circuit connected to the battery terminals. In IC1/6 shows a steady trend of +7.15 V, when the input voltage is greater than + 9.5V. The constant voltage is applied to IC1/5. In IC1/4 applies a voltage of the input, controlled by the trimmer TR1. The IC1 is act as voltage comparator . So when the voltage at IC1/4 is greater than the voltage at IC1/5, then the output of IC1/9, is low [L], the Q1 is off and the LED is off. To turn the LED should the voltage at IC1/4 be less than the reference voltage at IC1/6, where the output of IC1/9 will be high [H], the Q1 conducts and LED lights.

To configure the circuit will need an external power supply, which will be configured to output a +10.8 V, we apply the input circuit. Adjust the trimmer TR1, so that lights the LED, with no decrease in the voltage of power supply. The input terminals of the circuit should be connected directly to the battery terminals and may be used when using batteries 12V (Lead Acid).

Split Power Supply Circuit 22V DC

2011-11-02T03:04:00.000-07:00

This is the circuit diagram of split power supply circuit which will give a regulated DC voltage (+)22V ; GND and (-)22V. This is an old regulated power supply design which built using active components of dioda zeners and transistors to give regulated output.

This is a very basic voltage regulator circuit, without any additional features such as foldback current limiting, and doesn't have the same performance as an IC regulator such as 78xx series.

Variable Lab Power Supply 0-24V / 4A

2011-10-26T14:36:00.000-07:00

Variable lab power supply 0-24V / 4A, it is a laboratory power supply with output voltage continuously adjustable from 0 V to 24 V DC, remote voltage sense capability (Sense internal/external). It has output current limit which is continuously adjustable from 0.04 A to 4 A and output current which can be limited continuously or output shut down (Limit/cut).

Remote sensing means that there are actually two extra wires which sense the delivered voltage at the load and compensate for any voltage drop along the cables which carry the delivered electric current. This improves voltage regulation at the load significantly but needs two extra wires for the sensing. A switch will allow internal sensing at the output terminals for easier operation when remote sensing isn't necessary.

Read the detailed explanation about Variable Lab Power Supply 0-24V / 4A

Variable Power Supply Circuit 3-24V / 2A

2011-10-23T14:44:00.000-07:00

This the variable power supply with regulated output. The circuit can be altered from 3V to 25V and the electric current is limited to 2 amps as shown. But it's possible to be increased to 3 amps or more by applying a smaller current sense resistor (0.3 ohm).

The power transistor 2N3055 and 2N3053 is used to boost the output current and it should be mounted on suitable heat sinks and the current sense resistor should be rated at 3 watts or more.

2000V High Voltage Low Current Power Supply

2011-09-26T00:46:00.000-07:00

This is a high voltage, low current power supply circuit which will give you high power voltage about 2000V output from 15VDC input.

A high voltage power supply can be a really beneficial source which could be properly utilized in a lot of applications like biasing of gas-discharge tubes and radiation detectors and so on. Such a power supply could also be utilized for protection of property by electric charging of fences. Here the electric current requirement is of the order of several microamps. In such an application, high voltage would basically exist in between a ‘live’ wire and ground. When this ‘live’ wire is touched, the discharge starts through body resistance and it provides a non-lethal but deterrent shock to an intruder. The circuit is built around a single transistorised blocking oscillator. An vital element in this circuit could be the transformer. It could be fabricated on quite easily available ferrite cores. Two ‘E’ sections of the core are joined face-to-face after the enamelled copper wire wound on former is placed in it.

Here the transistor winding:

2000V High Voltage Low Current Power Supply Source:
http://www.electronicsforu.com/efylinux/circuit/cir96.htm

15V Switching Power Supply Circuit

2011-09-15T05:27:00.000-07:00

Switching power supply circuit, give you 15V DC output with 1A electric current. It will be 15 watt power output. Looks like this circuit come from Rusia, some components type might not available in your location, you should find the substitude of component parts first.

Source: Switching power supply 15 Watt

LT1086 Negative Voltage Regulator

2011-09-07T22:51:00.000-07:00

This is the efficient negative voltage regulator circuit built based IC LT1086.

One way to provide good negative-voltage regulation is with a low-dropout positive-voltage regulator operating from a well-isolated secondary winding of switch-mode circuit transformer. The technique works with any positive-voltage regulator, although highest efficiency occurs with low-dropout types.

Under all loading conditions, the minimum voltage difference between the regulator VIN and V0UT pins must be at least 1.5V, the LT1086's low-dropout voltage. If this requirement isn't met, the output falls out of regulation. Two programming resistors, R1 and R2, set the output voltage to 12 V, and the LT1086's servo the voltage between the output and its adjusting (ADJ) terminals to 1.25 V. Capacitor C1 improves ripple rejection, and protection diode D1 eliminates common-load problems.

Since a secondary winding is galvanically isolated, a regulator's 12 V output can be referenced to ground. Therefore, in the case of a negative-voltage output, the positive-voltage terminal of the regulator connects to ground, and the -12 V output comes off the anode of D1. The VIN terminal floats at 1.5 V or more above ground.

LT1086 Negative voltage regulator circuit diagram.

Offline Switching Power Supply Circuit (5V - 10A / 50W)

2011-08-31T15:19:00.000-07:00

The following diagram is the circuit diagram of offline switching power supply circuit:

Circuit Diagram:

Parts List:

This switching power supply is using a MOSFET. For 220V AC voltage input, use BUZ80A/IXTP4N8 MOSFET. And for 110V AC input voltage, use GE IRF823 MOSFET. The output will be 5 Volt DC with electric current can be reach 10A.

Positive Regulator Circuit with PNP and NPN Transistor Boost

2011-08-26T02:24:00.000-07:00

Here the schematic diagram of positive regulator with PNP and NPN transistor boost. Inside the circuit, Q1 and Q2 are wired in the classic SCR or thyristor configuration. In which higher input voltages or minimum element count are needed, the circuit for thyristor boost could be applied. The thyristor is working in a linear mode with its cathode as the control terminal and its gate to be the output terminal. This is known to be the remote base configuration.

5V to Isolated 5V Converter Circuit

2011-08-18T02:08:00.000-07:00

This is the circuit diagram of 5V to Isolated 5V Converter, rated at 20mA electric current.

In this converter circuit, a negative output voltage dc to dc converter generates a -5V output at pin A. In order to generate -5V at point A. the primary of the transformer must fly back to a diode drop more negative than -5V. If the transformer has a tightly coupled I : 1 turns ratio. there will be a 5 V plus a diode drop across the secondary. The IN5817 rectifies this secondary voltage to generate an isolated 5V output. The isolated output is not fully regulated since only the -5V at point A is sensed by the MAX635.

5V Regulated Power Supply Circuit with Over Voltage Protection

2011-08-13T15:01:00.000-07:00

The 5V regulated power supply for TTL and 74LS series integrated circuits, has to be really precise and tolerant of voltage transients. These IC's are effortlessly damaged by short voltage spikes. A fuse will blow when its electric current rating is exceeded, but demands several hundred milliseconds to respond. This circuit will react in several microseconds, triggered when the output voltage exceeds the limit of the zener diode.

This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take position in a few microseconds or less, and so provides considerably higher protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in some microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic IC's will probably be saved. The fuse will nonetheless take just a few hundred milliseconds to blow but this just isn't significant now since the supply towards the circuit is already at zero volts and no damage can be completed. The dc input towards the regulator needs to be a few volts greater than the regulator voltage. Inside the case of a 5v regulator, I would suggest a transformer with secondary voltage of 8-10volts ac.

Voltage Regulator with FET KP103K

2011-08-02T00:09:00.000-07:00

This is a voltage regulator circuit built based FET KP103K. The FET VT3 acts as a dynamic load for the transistor VT2. Because of this factor increases the voltage regulation: when the input voltage from 11 to 19 V output voltage varies within ± 60 mV. Rated output voltage using Zener type D814B is 9 V.

Voltage Regulator with FET KP103K circuit source: Voltage Regulator with FET

1.5V-25V DC Variable Power Supply

2011-07-26T01:32:00.000-07:00

This is 1.5V-25V DC Variable Power Supply. The power supply use KR142EN14 or LM317 as regulator component. KR142EN14 or LM317 is capable to handle electric current up to 2A. You may use LT1083/84/85 to handle electric current of 7A/5A/3A. Resistor R9 is used as a current sensor to an ammeter.

Components list:

R1 : 4K3
R2 : 18K
R3 : 100
R4,R8 : 100K
R5 : 1K
R6 : 240
R7 : 4K7 ( Variable resistor )
R9 : 0.33 E
C2 : 0.1uF
C3 : 10000uF/40V

C4 : 100uF/25V
D1 : KY202
D2 : KD521
D3 : D311
D4 : KC147
T1 : KT814B
T3 : KT209
T4 : KT3102
IC1 : KR142EN14 (LM317)

Circuit source: 1.5V-25V power supply with preregulator

LT1070 Boost Converter Circuit, 5VDC to 12VDC

2011-07-20T15:43:00.000-07:00

This is a converter circuit which will convert 5VDC input to become 12VDC output. The circuit is based LT1070 which also will boost the current output.

About LT1070:
The LT^®1070/LT1071 are monolithic high power switching regulators. They can be operated in all standard switching configurations including buck, boost, flyback, forward,inverting and “Cuk”. A high current, high efficiency switch is included on the die along with all oscillator, control and protection circuitry.

Boost Converter circuit reference, download: LT1070 datasheet

Cheap Low-Dropout 12V / 3A Linear Regulator

2011-07-15T04:27:00.000-07:00

The following diagram is the cheap Low-Dropout linear regulator circuit.

This linear post regulator circuit provides 12 V at 3 A. It applies TL431 reference U1 which, without additional amplification, drives TMOS MTP3055A gate Q1 series pass regulator. Bias voltage is applied through R1 to Q1's gate, which is protected against overvoltage by diode CR1. Frequency compensation for closed-loop stability is provided by C1.

Circuit Characteristics:
Dropout voltage: 0.6 V
Line regulation: ±5 mV
Load regulation: 10 mV
Output ripple: 10 mV pk-pk

NiCd NiMH Battery Charger using PIC16C711

2011-07-10T06:33:00.000-07:00

This is the battery charger circuit for NiCd and NiMH battery tipe. The circuit is using microcontroller PIC16C711 for constant current supply. A constant current supply is switched on and off as required by a micro-controller. The microcontroller senses the battery voltage and internally uses an analog to digital converter to read the battery voltage. The microcontroller, requires its own 5V regulated supply and displays the current charging status on two LEDs. The smallest and cheapest micro-controller that could be used to perform the Analog to Digital function and still have the necessary functions and control lines to do this is the PIC16C711.

Visit this page for full explanation about this NiCd NiMH Battery Charger circuit

Tracking Preregulator circuit

2011-07-07T07:07:00.000-07:00

The following diagram is the schematic diagram of tracking preregulator circuit uses LM308, LM360, 2N2905.

15A DC Voltage Regulator

2011-07-03T03:17:00.000-07:00

The following circuit diagram is a 15A DC voltage regulator based LM338

Electronic Power Controller Circuit

2011-06-28T21:28:00.000-07:00

This is an electric power controller which implemented the bidirectional triode thyristor(TRIAC). This circuit can manage the electrical power using the a single variable resistor.

This circuit is applied for the dimmer which adjusts the light from the bulb. This circuit adjusts the quantity of the electrical current which flows via the load together with the bidirectional triode thyristor and controls the electric power. It truly is only the alternating voltage that may be controlled with this circuit and it is impossible to perform the control in the DC voltage.

Simply because it controls the passing time in the alternating current by the bidirectional triode thyristor, the electrical current which flows via the load is not the clean sine wave type. Due to the fact it's, there is limitation in the equipment which may be controlled with this circuit. The bidirectional triode thyristor is usually called by the trade name TRIAC.

The equipment which can be controlled

The equipment which works by the resistance. Such as the the tungsten-filament lamp, the soldering iron and so on.
The equipment which is using the AC series motor(with the brush). Such as the drill, the electric fan, the cleaner and so on.

The equipment which can not do the control

The fluorescence light.
The synchronous motor(using the capacitor)

Detailed Electronic Power Controller Circuit project: http://www.piclist.com/images/www/hobby_elec/e_ckt24.htm

Voltage Double Circuit with timer IC 555

2011-06-26T21:08:00.000-07:00

This is a voltage double circuit which build using well-known timer IC 555. The circuit is very simple, and is easily to build. Construction is not crucial.

Here the schematic diagram:

Rectifier diodes should be ultrafast (UF4004 or similar), or you can use 1N4148 signal diodes. Losses will be slightly higher if you use signal diodes, or lower if you wanted to go to the trouble of using Schottky diodes - the latter are not warranted in such a simple circuit (IMO). The zener diode is to protect the circuit against transient overvoltage, and is optional.

Voltage Double Circuit with timer IC 555
source: http://sound.westhost.com/project95.htm

Current Output Doubler after 78xx Regulator

2011-06-23T18:01:00.000-07:00

This is about how to increase the current output limit after voltage regulating process using regulator 78xx series. As we know, current output after 78xx regulator is about 1 - 1.5A. With this circuit, you will be able to get higher current output from regulated power supply.

Components List:
R1, R2 = 4.7 K
C1, C2 = 4700 uF / 16V
C3 = 47,000 uF / 35V
D1,D2, D3 = 1N5401 ( 3 Amp Diodes )
D4 & D5 – Light Emitting Diodes (LED)**
IC1, IC2 – 78xx series regulator IC ( 7805 for 5V, 7812 for 12V etc.)

Visit this page for detailed instruction and explanation how to doubling the current output after regulate the voltage with IC regulator 78xx series.

Voltage Doubler Circuit: 12VDC to 18VDC or 24VDC

2011-06-20T00:07:00.000-07:00

Here the schematic diagram:

This circuit will convert 12-V power supply to become a 24VDC and 18VDC. Use this circuit with almost any PNP or NPN power transistor.

Component Parts list:
U1: NE 555 timer.
C1 and C2: 50μF/25V
Q1: TIP 29, TIP120, 2N4922, TIP61, TIP110, or 2N4921.
Q2: TIP30, TIP125, 2N4919, TIP62, TIP115, or 2N4918.

3A Switching Regulator Circuit

2011-06-15T15:43:00.000-07:00

Here the simple and cheap switching regulator circuit which capable to deliver 3A electric current.

Use the heatsink on the transistor to prevent damage due to overheating on its.

UPS Circuit for Cordless Telephone

2011-06-10T09:52:00.000-07:00

This is the schematic diagram of UPS CIrcuit for Cordless Telephone:

When the AC mains is present, the very same is converted into DC and fed to the inverter. A component of the mains rectified output is being used to charge the battery. When the mains power fails, the DC supply to the inverter is from the battery and from this is obtained AC at the inverter output.

The circuit wired around IC CD4047 is an astable multivibrator operating at a frequency of 50 Hz. The Q and Q outputs of this multivibrator directly drive power MOSFETS IRF540. The configuration applied is push-pull type. The inverter output is filtered as well as the spikes are reduced working with MOV (metal oxide varistor). The inverter transformer chosen is an ordinary 9V-0-9V, 1.5A mains transformer readily offered inside the market. Two LEDS (D6 and D7) indicate the presence of mains/battery.

The mains supply (when present) is stepped down, rectified and filtered working with diodes D1 via D4 and capacitor C1. A component of this supply is also employed to charge the battery. In place of a single 12V, 4Ah battery, one may use two 6V, 4Ah batteries.

The circuit may be easily assembled on a general-purpose PCB and placed inside a metal box. The two transformers may be mounted on the chassis of the box. The identical circuit can deliver up to 100W, provided the inverter transformer and charging transformer are replaced with higher present rating transformers, so that the system may be used for some other applications too.

Download UPS CIrcuit for Cordless Telephone detailed explanation in pdf document here

Dual Polarity Power Supply +33V, 0 , -33V

2011-06-06T04:17:00.000-07:00

The following diagram is the example of dual polarity power supply circuit which will give you (+33V) ; (0) and (-33V) DC voltage. This circuit is usually used for power amplifier circuit which require dual polarity power supply to work.

Components List:
R1 = 3K3 1/2W
C1 = 10nF/1000V
C2,C3 = 4700µF/50V
C4,C5 = 100nF/63V
D1 = 200V 8A Diode bridge
D2 = 5mm. Red LED
F1,F2 = 3.15A Fuses with sockets
T1 = 220V Primary, 25 + 25V Secondary, 2A minimum
PL1 = Male Mains plug
SW1 = SPST Mains switch

source: redcircuits.com

Unregulated Dual Polarity Power Supply

2011-06-01T16:20:00.000-07:00

This is the schematic diagram of Unregulated Dual Polarity power supply.

Unlike 78xx and 79xx dual polarity regulated power sypply and LM317/LM337 dual polarity regulated power supply which have limited current output and voltage (have limited supply power), this unregulated power supply will give you more power.

This kind of circuit usually used for power amplifier which need high supply power, or as high current lead acid battery charger (single polarity only).

The component value is flexible refer to your needs. For example: if you need power supply for 100W amplifier, then the component value are:

Transformer: 3A minimum (center tap)
Diodes: 3A diode (1N5401, 1N5402, 1N5403 etc)
Electrolytic capacitor: 4x minimum of 4700uF/50V (the higher is better - check the capacitor voltage, change it for higher voltage. example: use 63V capacitors for 45V power supply output.)

5V DC / 10A Offline Switching Power Supply

2011-05-29T04:42:00.000-07:00

Offline switching power supply which resulting 5VDC/10A output from 110/220V AC home power electric. See the parts list, there should be different MOSFET type for 110V anf 220V volatage input.

Below the diagram:

And here the parts list:

The schematic shows a 50-W power supply with a 5-V 10-A output. It is a flyback converter operating inside the continuous mode. The circuit has functionality of a main side and secondary side controller will full-protection from fault conditions such as overcurrent. When the fault condition has been removed, the power supply will go into the soft-start cycle just before recommencing normal operation.

Positive Voltage Regulator Circuit with PNP Boost

2011-05-26T03:22:00.000-07:00

The IC8211 presents the voltage reference and regulator amplifier, although Q1 will probably be the series pass transistor. R1 defines the output current of the IC8211, although C1 and C2 present loop stability and as well act to suppress feedthrough of input transients to the output supply. R2 and R3 define the output voltage as follows:

Furthermore, the values of R2 and R3 are preferred to create a bit volume of standing current in Q1, which provides additional stability margin on the circuit.Where accurate setting of the output voltage is needed, either R2 or R3 could possibly be designed adjustable. If R2 is designed become adjustable,then the output voltage will vary linearly with the shaft angle; nevertheless, if the potentiometer wiper was to open the circuit, the output voltage would rise. Normally, for that reason, it is far more beneficial to provide R3 adjustable, due to the fact this can give fail-safe operation.

Low Forward-Drop Power Supply Circuit

2011-05-21T19:16:00.000-07:00

Check out the signal output... this power supply will cut off the negative amplitudo and pass the positive AC signal.

A TMOS power FET , Q1 , and LM393 comparator supply a higher performance rectifier circuit. When V_Aexceeds V_B, U1's output turns into higher and Q1 conducts. Conversely, when V_B exceeds V_A, the comparator output gets low and Q1 does not conduct.

The forward drop is determined by Q1's on resistance and latest I. The MTH40N05 has an on resistance of 0.028 Ohm; for I = 10 A, the forward drop is much less than 0.3 V. Typically, the very best Schottky diodes usually do not even start conducting below several hundred mV.

9V Stabilized Power Supply Circuit with LM723

2011-05-13T15:16:00.000-07:00

Here the 9V Stabilized power supply circuit. Built based IC 723 and featured with amp booster using 2N3055. The 2N3055 must be mounted on a coolrib/heatsink.

Schematic Diagram:

Components List:

R1 = 0.56 Ohm, 1 Watt, wire-wound type, 5%
R2 = 750 Ohm, 5%
R3 = 2K7 (2700 ohm)
P1 = potentiometer, 1K, Linear
C1 = 2200uF, 35V
C2 = 470pF
T1 = 115/10 VAC transformer. Center Tap (ct) not needed.
IC1 = uA723, LM723, or equivalent.
Q1 = 2N3055, NTE130, or substitute. (TO-3 case) Mount on a coolrib!
BR1 = 80V-5A (or better)

Circuit Notes:

C1 filters the noise and spikes off the AC. Adjust the circuit for 9V or 12V output voltage, or whatever voltage level your pc mini drill is using, with the P1 potentiometer.
Q1 can also be a MJ2955 in a TO-3 case.

Design by Tony van Roon
Source: http://www.sentex.ca/~mec1995/circ/9vstable.htm

24V Lead-Acid Battery Charger Diagram

2011-04-23T15:55:00.000-07:00

This circuit is a current limited lead acid battery charger built around the famous variable voltage regulator IC LM 317. The charging current depends on the value of resistor R2 and here it is set to be 700mA. Resistor R3 and POT R4 determines the charging voltage. Transformer T1 steps down the mains voltage and bridge D1 does the job of rectification. C1 is the filter capacitor. Diode D1 prevents the reverse flow of current from the battery when charger is switched OFF or when mains power is not available.

The schematic diagram:

Circuit Notes:

Assemble the circuit on a good quality PCB.
F1 can be a 2A fuse.
T1 can be a 230V primary, 35V/3A secondary step down transformer.
LM317 must be fitted with a heat sink.
If 3A Bridge is not available, make one using four 1N5003 diodes.
R2 = 0.85 ohm is not a standard value. You can obtain it by combining a 6.2 ohm and 1 ohm resistors in parallel.
To setup the charging voltage, power ON the charger and hook up a voltmeter across the output terminals and adjust R4 to make the voltmeter read 28V. Now the charger is ready and you can connect the batteries.
This battery charger is specifically designed for two 12V/7AH/6 cell lead acid batteries in series OR a 24V/7AH/12 cell lead acid battery.

Source: http://www.circuitstoday.com/24v-lead-acid-battery-charger-circuit

DC Battery Tester circuit

2011-04-08T21:51:00.000-07:00

This is a DC battery tester circuit diagram. The circuit will work for DC battery from 1.5V up to 9V.

Electronic Parts List:
R1 = 18K Ohm
R2 = 240 Ohm
R3 = 8.2K Ohm
R4 = 3K Ohm
R5 = 10 Ohm
M1 = Panel Meter (Any Panel Meter will work)

Source: dc battery tester

NiCad Battery Charger

2011-03-23T15:16:00.000-07:00

Simple NiCad battery charger with current and voltage limiting features. This circuit should be very easy to built.

Circuit source: NiCad Battery Charger

NiCad Battery Charger circuit

0-28V / 6A Regulated Variable Power Supply

2011-01-18T14:10:00.000-08:00

Parts list:

TR = 2 x 15 volt (30volt total) 6+- amps
D1...D4 = four MR750 (MR7510) diodes (MR750 = 6 Ampere diode) or 2 x 4 1N5401 (1N5408) diodes.
F1 = 1 Amp
F2 = 10 amp
R1 = 2k2 2,5 Watt
R2 = 240 ohm
R3,R4 = 0.1 ohm 10 watt
R7 = 6k8 ohm
R8 = 10k ohm
R9 = 47 0.5 watt
R10 = 8k2
C1,C7,C9 = 47nF
C11 = 22nF
C2 = 4700uF/50v - 6800uF/50v
C3,C5 = 10uF/50v
C4,C6 = 100nF
C8 = 330uF/50v
C10 = 1uF/16v
D5 = 1N4148, 1N4448, 1N4151
D6 = 1N4001
D10 = 1N5401
D11 = LED
D7, D8, D9 = 1N4001
IC1 = LM317
T1, T2 = 2N3055
P1 = 5k
P2 = 47 Ohm or 220 Ohm 1 watt
P3 = 10k trimmer

This is definitely an simple to create power supply which has reliable, clear and regulator 0 to 28 Volt 6/8 Ampere output voltage. By using two 2N3055 transistor, you'll get two times the amount of electric current.

Although the 7815 power regulator is going to kick in on brief circuit, overload and thermal overheating, the fuses within the primary section of the transformer and also the fuse F2 in the output will protected your power supply. The rectified voltage of: 30 volt x SQR2 = 30 x 1.41 = 42.30 volt measured on C1. So all capacitors ought to be rated at 50 volts. Caution: 42 volt is the voltage that might be around the output if one of the transistors ought to blow.

P1 allows you to 'regulate' the output voltage to anything between 0 and 28 volts. The LM317 lowest voltage is 1.2 volt. To have a zero voltage around the output I've put 3 diodes D7,D8 and D9 on the output of the LM317 to the base of the 2N3055 transistors. The LM317 optimum output voltage is 30 volts, but applying the diodes D7,D8 & D9 the output voltage is approx 30v - (3x 0.6v) = 28.2volt.

Calibrate your build-in voltmeter working with P3 and, of course, a good digital voltmeter is better solution.

P2 will certainly let you to set the limit of the optimum available electric current at the output +Vcc. When using a 100 Ohm / 1 watt variable resistor the current is limited to approx. 3 Amps @ 47 Ohm and +- 1 Amp @ 100 Ohms.

Lead Acid Battery Charger Schematic

2011-01-06T22:42:00.000-08:00

This circuit gives an initial voltage of 2.5 V per cell at 25℃ to rapidly charge the battery. The charging current decreases as the battery is charging, and when the current drops to 180 mA, the charging circuit reduces the output voltage of 2.35 V per cell, leaving the battery in a fully charged state. This lower voltage prevents the battery from overcharging, which would shorten its life.

The LM301A compares the voltage drop across R1 with an 18 mV reference set by R2. The comparator’s output controls the voltage regulator, forcing it to produce the lower float voltage when the battery-charging current, passing through R1, drops below 180 mA. The 150 mV difference in between the charge and float voltages is certainly set by the ratio of R3 to R4. The LEDs present the state of the circuit.

Temperature compensation assists stop overcharging, especially when a battery goes through wide temperature changes whilst becoming charged. The LM334 temperature sensor ought to be placed near or on the battery to lower the charging voltage by 4 mV/℃ for each cell. Because batteries require far more temperature compensation at lower temperatures, alter R5 to 30Ω for a tc of -5 mV/℃ per cell if application will see temperatures beneath -20℃.

The charger’s input voltage need to be filtered dc that's at the very least 3 V greater than the maximum required output voltage: approximately 2.5 V per cell. Choose a regulator for the highest possible current required: LM371 for 2 A, LM350 for 4 A, or LM338 for 8 A. At 25℃ and with no output load, adjust R7 for a V_OUT of 7.05 V, and adjust R8 for a V_OUT of 14.1V.

12V NiCAD Battery Charger

2010-12-18T19:53:00.000-08:00

This is the circuit diagram of 12V NiCAD battery charger. The battery charger charging rate is at 200mA/Hour.

The battery charger circuit will continue to charge the battery at 75 mA until the battery is fully charged, then it reduces the current to a trickle rate. It will fully recharge a dead/unpowered battery in 4 hours and the battery can be left in the charger indefinitely. To set the shut off point, connect a 270 ohm / 2 Watt resistor across the charge terminals and adjust the potensiometer for 15.5V across the resistor.

Variable Power Supply Circuit 6-12V

2010-12-12T02:40:00.000-08:00

The output voltage of this power supply circuit can be adjusted from 6 volt to 12 volt. The output voltage is regulated by Q1.

Parts List:

R1 = 470 ohm, 5%
R2 = 1K, 5%
P1 = 10K ohm Potentiometer
C1 = 1000uF/25V
T1 = 115[220]/8VAC transformer. Center Tap not needed.
Q1 = 2N1613, NTE128, or substitute. (TO-39 case) On coolrib!
BR1 = 40V, 4A. (Check max current of your mini-drill and add 2A)

Notes:

C1 filters the noise and spikes off the AC. If you find the circuit output too noisy add another electrolytic capacitor over the output terminals. Value can be between 10 and 100uF/25V.
10K-potentiometer used to adjust the output voltage.
The transformer input voltage refer to your home power source.
You may change the bridge diode with four rectifier diodes.

Battery Charger circuit for Lithium Battery

2010-11-16T22:29:00.000-08:00

The following diagram is the circuit diagram of battery charger that can be used to re-charge your lithium batteries.

The charging with a constant current of 60 mA for AA batteries for a sequestration of 2.4 V per cell, when the charge should be terminated. The charging system is indicated for the battery to several cells of 2-6 cells connected series or series / parallel arrangements. It is important that all cells are assembled in the package is in the same state-of charge (voltage) before loading. upper cut-off voltage is 15.6 V (6 x 2.6 V). ICL7665 is a voltage monitor with dualover / under voltage detection.

Battery Charger circuit for Lithium Battery

0-24V Digital Variable Power Supply

2010-10-13T17:47:00.000-07:00

The following circuit diagram is a variable power supply which controlled by PIC microcontroller. The LCD display is used to showing the actual value of output current voltage. This is a digital power supply, use the push on switch to adjust the output voltage and current value.

Schematic Diagram:

Visit the digital power supply circuit page for detail explanation

Logic Power Supply circuit with Overvoltage Protection

2010-09-28T21:29:00.000-07:00

Here the simple 5V regulated power supply circuit which featured overvolatage protection.

The circuit work:
This circuit uses the crowbar method, where a thyristor is employed and short circuits the supply, causing the fuse to blow. This will take place in a few microseconds or less, and so offers much greater protection than an ordinary fuse. If the output voltage exceed 5.6Volt, then the zener diode will conduct, switching on the thyristor (all in a few microseconds), the output voltage is therefore reduced to 0 volts and sensitive logic IC's will be saved. The fuse will still take a few hundred milliseconds to blow but this is not important now because the supply to the circuit is already at zero volts and no damage can be done. The dc input to the regulator needs to be a few volts higher than the regulator voltage.

Read more circuit explanation at http://www.zen22142.zen.co.uk/Circuits/Power/overvolt.htm

Negative Adjustable Power Supply

2010-08-22T23:18:00.000-07:00

This is a negative adjustable power supply. The power supply is regulated based on LM337T regulator IC. The LM337T is a regulator for negative voltage. This power supply output current is 1.5A max.

Schematic diagram:

Power Supply Input:

Component part list:
R1 = 330
R2 = 1K
VR1 = 10K 10-turn trimpot
C1 = 2200uF/50V
C2,4 = 100nF ceramic
C3,4 = 10uF/63V
D1-6 = 1N5403
REG IC = LM337T
Heatsink

This circuit is available in kit module at electronickits.com, you may buy the this power supply kit there. Here the manual of the kits which containing the schematic diagram, part list and the explanation of the power supply circuit.

Positive Adjustable Power Supply Circuit

2010-08-22T23:11:00.000-07:00

Below is a positive regulated adjustable power supply based on LM317T regulator IC. The LM317T is a regulator for positive voltage. This power supply output current is 1.5A max.

Schematic diagram:

Power Supply Input:

Component part list:
R1 = 330
R2 = 1K
VR1 = 10K 10-turn trimpot
C1 = 2200uF/50V
C2,4 = 100nF ceramic
C3,4 = 10uF/63V
D1-6 = 1N5403
REG IC = LM317T
Heatsink

This circuit is available in kit module at electronickits.com. Here the manual of the kits which containing the schematic diagram, part list and the explanation of the power supply circuit.

6VDC to 12VDC Converter circuit

2010-06-15T15:54:00.000-07:00

This is the circuit diagram of 6VDC to 12VDC Converter. With this circuit, you can doubled the input voltage of 6V DC to become 12V DC output voltage.

Component Parts:

R1, R4 = 2.2K
R2, R3 = 4.7K
R5 = 1K
R6 = 1.5K
R7 = 33K
R8 = 10K
C1,C2 = 0.1uF

C3 = 470uF/25V
D1 = 1N914
D2 = 1N4004
D3 = 12V 400mW Zener Diode
Q1, Q2, Q4 = BC547
Q3 = BD679
L1 See Notes

Circuit Notes:
1. L1 is a custom inductor wound with about 80 turns of 0.5mm magnet wire around a toroidal core with a 40mm outside diameter.
2. Different values of D3 can be used to get different output voltages from about 0.6V to around 30V. Note that at higher voltages the circuit might not perform as well and may not produce as much current. You may also need to use a larger C3 for higher voltages and/or higher currents.
3. You can use a larger value for capacitor C3 to provide better filtering.
4. The circuit will require about 2A from the 6V supply to provide the full 800mA at 12V.

6VDC to 12VDV Converter circuit, source:
http://www.high-voltage-lab.com/61/6v-to-12v-converter

Batteries charger and PSU circuit

2010-05-09T19:43:00.000-07:00

Here's a circuit diagram of the power supply and battery charger.

There are two parts in this circuit, ie the battery charger with a fixed output voltage, which is 5VDC. Another part is the regulated power supply that can be regulated output voltage between 2-9 volts.

source: http://www.electronics-lab.com

0-24VDC PIC Power Supply circuit

2010-03-17T19:27:00.000-07:00

This is a digital variable power supply circuit which controlled using microcontroller chip PIC family.

Circuit Diagram:

For detailed information, visit this Digital PIC Power Supply circuit page

Adjustable Power Supply 6-12VDC

2010-01-15T18:57:00.000-08:00

Here the another variable power supply which have adjustabled output voltage from 6-12 DC volt.

Parts List:
T1 = 115[220]/8 VAC transformer.
Q1 = 2N1613, NTE128, or substitute. Use heatsink!
BR1 = 40V, 4A. (Check max current of your mini-drill and add 2A)
R1 = 470 ohm, 5%
R2 = 1K, 5%
P1 = potentiometer, 10K
C1 = 1000uF, 25V

Notes:

C1 filters the noise and spikes off the AC. If you find the circuit output too noisy add another electrolytic capacitor over the output terminals. Value can be between 10 and 100uF/25V.
The output voltage is variable with the 10K-potentiometer.
The transformer input voltage refer to your home power source.

12V Lead-Acid Battery Monitor circuit

2009-12-25T04:32:00.000-08:00

This simple circuit makes it posible to monitor the charging process to a higher level. If you need more information then check out the LM3914 Datasheet.

Final adjustsments are simple and the only thing needed is a digital voltmeter for the necessary accuracy.

Connect an input voltage of 12.65 volt between the positive and negative poles and adjust the 10K trimmer potentiometer until Led 10 lights up. Lower the voltage and in sequence all other Led's will light up. Check that Led 1 lights up at approximately 11.89 volts. At 12.65 volt and higher the battery is fully charged, and at 11.89 is considered 'empty'.

The green Led's indicate that the battery capacity is more than 50%, the yellow Led's indicate a capacity of 30% - 50% and the red Led's less that 30%. This circuit, with the components shown, uses less than 10mA. Of course you can adapt this circuit to your own needs by making small modifications. The circuits above is set for 'DOT' mode, meaning only one Led at a time will be lit.

If you wish to use the 'BAR' mode, then connect pin 9 to the positive supply rail, but obviously with increased current consumption.

The LED brightness can be adjusted up- or down by choosing a different value for the 4K7 resistor connected at pin 6/7.

You can also change the to monitoring voltage level. For example, let's say you wanted to change to 10 - 13 volt, you connect 13volt to the input (+ and -) and adjust the 10K potentiometer until Led 10 lights up. Change temporarily the resistors at pin 4 with a 200 Kilo-ohm potentiometer and reconnect a voltage from 10 Volt to the input. Now, re-adjust the 200K potentiometer until Led 1 lights up. When you are satisfied with the adjustment, feel free to exchange the 200K potentiometer with resistors again.(after measuring the resistance from the pot, obviously).

The diode 1N4007 was included to protect the circuit from a wrong polarity connection. It is however strongly recommended to connect the monitor directly to the battery, in principle a connection to the cigarrette lighter would suffice but for reasons unknown at this time the voltage at that point is 0.2 volt lower than the voltage measured directly on the battery.

Mastech Assembled Power Supply 0-30V / 0-5A

2009-12-14T16:35:00.000-08:00

Do you need assembled power supply..? If your answer is yes, then this assembled digital power supply should be great to buy.

Product specification:

Two level of control for both current and voltage outputs: coarse and fine for ease of use
Adjustable outputs: 0-30V and 0-5A
Input voltage: 110V AC and 220V AC switchable
Ripple noise: CV <= 0.5 mV RMS, CC <= 3 mA RMS

You can BUY THIS POWER SUPPLY at Amazon.com

Simple battery charger circuit for car battery

2009-11-28T21:00:00.000-08:00

This is a very simple battery charger for your car battery. The most expensive part of this circuit is a 5 A transformer. A car battery has very high value of electric current, so it's require battery charger with high electric current output.

Power Supply failure alarm

2009-11-28T15:34:00.000-08:00

This is an power supply failure alarm which will give you an alert when the power supply getting off or fail to supply. It employs an electrolytic capacitor to store adequate charge, to feed power to the alarm circuit which sounds an alarm for a reasonable duration when the supply fails.

To calibrate the circuit, first connect the power supply (5 to 15V) then vary the potentiometer VR1 until the buzzer goes from on to off.
Whenever the supply fails, resistor R2 pulls the base of transistor low and saturates it, turning the buzzer ON.

Take a note that this circuit will be work only on power supply with output voltage 5 - 15 Volt DC.

Source: http://www.electronic-circuits-diagrams.com/alarmsimages/alarmsckt2.shtml

General Static and Adjustable Power Supply circuit

2009-10-26T00:08:00.000-07:00

Below general power supply circuit has 2 static output type, stabled output at 5VDC and adjustabled output or variable output.

Here the circuit diagram:

The circuit is based on the regulator IC 7805. It has only 3 connections (input, output and ground) and it provides a fixed output. The last two digits of the part number specify the output voltage, eg. 05, 06, 08, 10, 12, 15, 18, or 24. The 7800 series provides up to 1 amp load current and has on-chip circuitry to shut down the regulator (rather than blowing out) if any attempt is made to operate it outside its safe operating area. (If this happens to you, let the chip cool down and attach the heatsink.).

Visit this page more detail about general power supply.

3-30V DC / 3A Variable Power Supply circuit with IC 723

2009-10-16T22:04:00.000-07:00

Featured with short circuit protection and overload protection, this variable regulated power supply will is very nice for your electronic equipments. The voltage output range will be 3-30 volt DC with 3A current.

Download the manual of this circuit include the schematic diagram and part list from HERE

Source: circuitdiagram.net

Bench Power Supply

2009-10-05T18:33:00.000-07:00

This is the schematic diagram of bench power supply . This bench powersupply will be great to support your activity if you are an electronics hobbyst:

Take a note that based on the diagram, this circuit require 120V AC to 17V AC Center Tapped Transformer. If your country use 220V AC home electric source, you MUST change the Transformer 220-240V AC to 18V AC Center Tapped Transformer.

More information of this bench power supply, visit this page

Dual Polarity Regulated Power Supply circuit with IC 78xx/79xx

2009-10-03T01:57:00.000-07:00

This is a regulated power supply circuit with dual polarity output. There are 3 output that are (+) voltage, (0) Grounding, and (-) voltage. The current output max about 0.3-0.5 A. IC 78xx is used as positive voltage regulator while IC 79xx is used as negative voltage regulator.

You need center tapped (CT) transformer 0.5-1A for this circuit. Use transformer voltage output refer to your need. For example, if you need 12v output, you should connect J1 to 15v transformer output, J2 connected to 0v and J3 connected to another 15V.

High Current Power Supply Circuit with 2N3055

2009-09-26T19:05:00.000-07:00

This is a unregulated dc power supply circuit which have ability to handle high current load.

Component parts:

R1_________ 680 Ohm 1/4 Watt Resistor
C1_________ 20,000 - 50,000uF 20-40 Volt Capacitor
C2, C3_____ 100uF/50 Volt Capacitor
C4_________ 0.1uF 50 Volt Capacitor
C5_________ 0.01uF 50 Volt Capacitor
D1_________ Zener Diode
Q1_________ 2N3055 Or Other
T1_________ Transformer
BR1________ Bridge Rectifier
S1_________ SPST 250 VAC 10 A Switch
MISC_______ Case, Line Cord, Heatsink For Q1, Binding Posts For Output

NOTES:

D1 should be rated at about one volt higher than then desired output of the supply. A half watt diode will do.
Q1 can be a transistor similar to the 2N3055.
T1 should be about 5 volts higher than the desired output of the supply, and rated for about one amp more of current. The voltage overhead is required by the regulator section. The extra current is to keep the transformer from over heating.

The choice of BR1 will depend on the voltage and current of your transformer. The rectifier should be rated for 50 volts more than the transformer, and 5 amps more than the transformer.

The value of R1 will be smaller when supplying high currents. Expiriment until you get what you need.
You are going to need to heatsink Q1 and BR1. Use a small PC case style fan unless you are going to run large heatsinks.

Uninterruptible Power Supply circuit

2009-09-21T03:24:00.000-07:00

Here the Uninterruptible Power Supply (UPS) circuit with PIC17C43 microcontroller. Your UPS will be automatically controlled by the microcontroller.

UPS systems are traditionally designed using analog components. Today these systems can integrate a microcontroller with AC sine wave generation, offering the many benefits.

The PIC17C43 microcontroller handles all the control of the UPS system. The PIC17C43 is unique because it provides a high performance and low cost solution not found in other microcontrollers.

Download the document of Uninterrupted Power Supply

5-18V Stabilized Power Supply

2009-08-23T23:46:00.000-07:00

This power supply will give you fixed regulated output at 5V, 6V, 9V and 12V, while the 18V output is unregulated. You could add some regulated IC like LM7815 or 7818 if you need higher output voltage.

This circuit provide an audio indicator that will act like an alarm if any circuit short contact.

General DC Power Supply with uA723

2009-08-15T21:53:00.000-07:00

This is the power supply circuit for general purpose usage.

The supply can be used for supply output voltages from 1 to 35V. The line transformer should be selected to give about 1.4 times the desired output voltage from the positif side of filted capacitor C1 to ground. Potensiometer R2 sets the output voltage to the desired value by adjusting the reference input. Rsc is the current limit set resistor.

For example, if the maximum current output is to be 1A, Rsc=0.65/1.0 = 0.65 Ohm. The 1KOhm resistor,R5, is a light-loaded resistor designed to improve the no-load stability of the supply.

Universal Battery Charger

2009-08-12T02:07:00.000-07:00

Battery charger for general purpose usage.

The charger's output voltage is adjustable and regulated, and has an adjustable constant-current charging circuit that makes it easy to use with most NiCad batteries. The charger can charge a single cell or a number of series-connected cells up to a maximum of 18V.

Power transistors Q1 and Q2 are connected as series regulators to control the battery charger's output voltage and charge-current rate. An LM-317 adjustable voltage regulator supplies the drive signal to the bases of power transistor Q1 and Q2. Potensiometer R9 sets the output-voltage level. A current sampling resistor, R8 (a 0.1 ohm/5W unit), is connected between the negative output lead and circuit ground. For each amp of charging current that flows through R8, a 100mV output is developed across it. The voltage developed across R8 is fed to one input of comparator U3. The other input of the comparator is connected to variable resistor R10.

As the charging voltage across the battery begins to drop, the current through R8 decrease. Then the voltage feeding pin 5 of U3 decreases, and the comparator output follows, turning Q3 back off, which completes the signal's circular path to regulate the battery's charging current.

The charging current can be set by adjusting R10 for the desired current. The circuit's output voltage is set by R9

Adjustable Power Supply 3-30V/2.5A

2009-08-05T18:53:00.000-07:00

This is an adjustable power supply circuit, also known as variable power supply. . You may use this circuit for general purpose usage.

Here the schematic diagram:

Component list:

R1 = 560R 1/4W	C1 = 100nF
R2 = 1,2 K 1/4W	C2 = 2200uF 35-40V
R3 = 3,9 K 1/4W	C3 = 100 pF
R4 = 15K 1/4W	C4 = 100uF/ 35V
R5 = 0,15R 5W

D = B40 C3300/2200, 3A rectifier bridge
P1 = 10K potesiometer	TR1 = BD 135
IC = LM723	TR2 = 2N3055

Bottom PCB layout:

Top PCB layout (Components placement):

For complete explanation, circuit's works and how to build this circuit into the box, download the full tutorial here

Variable DC Power Supply with 2N3055

2009-07-31T18:23:00.000-07:00

This is variable power supply for multi purpose usage and very useful to supply your electronic tools or your projects. Voltage range will be 0.7 - 24V and the urrent limiting range is 50mA - 2A.

Components:

P1____________500R   Linear Potentiometer
P2_____________10K   Log. Potentiometer

R1,R2__________2K2  1/2W Resistors
R3____________330R   1/4W Resistor
R4____________150R   1/4W Resistor
R5______________1R     5W Resistor

C1__________3300µF   35V Electrolytic Capacitor (see Notes)
C2_____________1µF   63V Polyester Capacitor

D1,D2_______1N5402 200V 3A Diodes
D3____________5mm. Red LED

Q1___________BC182  50V 100mA NPN Transistor
Q2___________BD139  80V 1.5A  NPN Transistor
Q3___________BC212  50V 100mA PNP Transistor
Q4 _________2N3055  60V 15A   NPN Transistor

T1____________220V Primary, 36V Center-tapped Secondary
             50VA Mains transformer (see Notes)
PL1___________Male Mains plug
SW1___________SPST Mains switch

Notes:

P1 sets the maximum output current you want to be delivered by the power supply at a given output voltage.
P2 sets the output voltage and must be a logarithmic taper type, in order to obtain a more linear scale voltage indication.
You can choose the Transformer on the grounds of maximum voltage and current output needed. Best choices are: 36, 40 or 48V center-tapped and 50, 75, 80 or 100VA.
Capacitor C1 can be 2200 to 6800µF, 35 to 50V.
Q4 must be mounted on a good heatsink in order to withstand sustained output short-circuit. In some cases the rear panel of the metal box in which you will enclose the circuit can do the job.
The 2N3055 transistor (Q4) can be replaced with the slightly less powerful TIP3055 type.

20A Regulated Power Supply

2009-07-20T21:01:00.000-07:00

Here the regulated power supply circuit that will give you current output up to 20A depends the number of power transistor used in the circuit.

You can build the box like this:

here te schematic diagram:

for further instruction, visit this page

Dual Polarity Power Supply with LM317/LM337

2009-07-20T20:27:00.000-07:00

This is a regulated dual polarity power supply (download schematic and pcb layout HERE):

The output of this circuit will be positif output(+), normal/ground output(0) and negative output(-). IC LM317 is used to regulate the positive output and LM337 is used to regulate the negative output. You should use TAP transformer for this circuit and heatsink for the IC.

Please visit this page for complete explanation
Another dual polarity power supply circuit, visit here

Variable Power Supply with L200

2009-07-17T02:06:00.000-07:00

This inexpensive variable power supply circuit with L200. The output current is up to 2A and the output voltage depends to the output voltage from transformer. VR 47R used for current adjustment and the VR10K used for output voltage adjustment.

1-32V Variable Power Supply based on LM338

2009-07-13T19:19:00.000-07:00

This is regulated variable power supply circuit based on Transistor LM338. Short circuit protection added in this circuit.

1.3V-12.2V, 1A Variable Power Supply

2009-07-11T17:48:00.000-07:00

This is a simple but reliable power supply circuit based one of the oldest integrated voltage regulators of them all - the LM723.

Please visit this page for complete explanation.

Variable Power Supply with Transistor

2009-06-14T17:58:00.000-07:00

Component parts list:

P1____________500R Linear Potentiometer
P2_____________10K Log. Potentiometer

R1,R2___________2K2 1/2W Resistors
R3____________330R 1/4W Resistor
R4____________150R 1/4W Resistor
R5______________1R 5W Resistor

C1___________3300µF 35V Electrolytic Capacitor (see Notes)
C2______________1µF 63V Polyester Capacitor

D1,D2________1N5402 200V 3A Diodes
D3_____________5mm. Red LED

Q1____________BC182 50V 100mA NPN Transistor
Q2____________BD139 80V 1.5A NPN Transistor
Q3____________BC212 50V 100mA PNP Transistor
Q4 __________2N3055 60V 15A NPN Transistor

T1_____________220V Primary, 36V Center-tapped Secondary
50VA Mains transformer

PL1____________Male Mains plug

SW1____________SPST Mains switch

Notes:

P1 sets the maximum output current you want to be delivered by the power supply at a given output voltage.
P2 sets the output voltage and must be a logarithmic taper type, in order to obtain a more linear scale voltage indication.
You can choose the Transformer on the grounds of maximum voltage and current output needed. Best choices are: 36, 40 or 48V center-tapped and 50, 75, 80 or 100VA.

Variable Power Supply

2009-06-06T17:13:00.000-07:00

Here a variable power supply circuit which the output voltage can be adjusted. The stabilizer IC may be changed with different value as needed, example 7815 for 15v maximum voltage.

Component Parts List:
T1 Transformer 10:1 Secondary 24V @ 2A
BR1 Bridge Rectifier 50V PIV 2A rating
C1 4700u (35V)
C2 0.001u
C3 2200u (35V)
C4 0.001u
C5 4.7u (25)
C6 0.01u
R1 10k potentiometer
L1 see text
U1 7805 N.B. This may be changed for different output voltages e.g. 7812 for higher output voltage
ZD1 15V zener @ 1.3W

The specific inductance of the ferrite (core)is important. A core should be chosen to work within the specific frequency as stated by the manufacturer. L1 is a powder core and has 32 turns of 0.75mm wire.

The transformer has a 240V primary and has a secondary rated 24V at 2A. The bridge rectifier contains 4 diodes, their current rating needs to be high with respect to the transformers output current; if not the current may damage the diodes. C1 is the mainfiltering capacitor, the supply is further smoothed by the combination of L1 and C3. C2 and C4 are decoupling capacitors; their action further reduce ripple factor.

The regulator, U1 utilizes the action of zener diode ZD1 which is in parallel with the potentiometer, R1. The tuning action of R1 produces a variable regulator output. The output voltage is variable from the regulator output to the regulator output plus the zener voltage. E.G. A 7805 regulator and 10V zener give an output adjustable from 5 to 15 Volts. The regulator may be changed to provide different output voltages as may the zener. the zener should be rated a minimum of 1.3 Watts.

+50V / 3A Stabilized and Regulated Power Supply

2009-05-27T18:32:00.000-07:00

Here the +50V / 3A Stabilized and Regulated Power Supply.

schematic diagram:

component parts list:

R1= 10Kohm
R2= 1 ohm 5W
R3= 3.9 ohms 1W
R4= 6.8Kohm 1W
R5= 390 ohms 1W
R6= 100Kohm 0.5W
R7= 1.2Kohm 1W
R8= 1.8Kohm 0.5W
R9= 3.3Kohm 0.5W
RV1= 470 ohms pot.

Q3= BC303 or BC461
D1....4= Bridge 15A
D5= LED RED 5mm
C1-2-4= 4700uF 100V
C3-5= 100nF 250V MKT
D6-7= 10V 1W Zener
D8-9-10= IN4007
Q1= 2N3055 on heatsink
T1= 230Vac / 55V 3A
Q2= BD162 or BD243 or BD543

Note:
It 's a circuit that can give in his exit + 40V until + 60V 3A, with simultaneous stabilization. The materials that use is very simple and will not exist difficulties in the manufacture, is enough you are careful certain points:

For output voltages smaller of + 50V until + 40V, the Q1 is hot enough, so that it needs one big heatsink.
For output voltages bigger of + 50V up to + 70V, the stabilization is not satisfactory.

Conclusion: ideal output voltage is + 45V until + 60V. In the circuit potensiometer RV1, is used in order to we change the output voltage between + 40V until + 70V, we can however and perhaps it should, him we replace with two constant resistors, when finished the regulation, in the desirable price. The reason is, that with time is presented change of output voltage, up to 3V, with connected potensiometer.

ATTENTION!!! The positive exit correspond in point [ A ] and the exit of 0V in point [ B ], which should not be connected in the ground.

Source:
http://users.otenet.gr/~athsam/power_supply_50V_3A.htm

0-15V / 1A Adjustable Power Supply

2009-05-27T18:20:00.000-07:00

This is 0-15 volt / 1 Ampere power supply circuit diagram. This is very simple and easy to built, the output is stabilized and regulated. Maximum output 15V and 1 Ampere, u can use this circuit for common electronic devices like radio, cd player, mini amplifier or just for your experimental circuits.

Components list:

R1= 56ohm 2W
R2= 330ohm Lin. pot.
C1= 2200uF 35V
C2= 100uF 35V
C3= 10uF 25V
C4= 220uF 25V
C5= 100nF 100V
Q1= 2N3055
GR1= 4 X 1N4007
D1= 18V 1.5W zener
T1=220V@18V 1.5A

12V 30A Regulated Power Supply

2009-04-26T19:20:00.000-07:00

Very high current regulated power supply. This circuit require a transformer which have output 24v / 35A. It should be an expensive circuit :(

Notes:
The input transformer is likely to be the most expensive part of the entire project. As an alternative, a couple of 12 Volt car batteries could be used. The input voltage to the regulator must be at least several volts higher than the output voltage (12V) so that the regulator can maintain its output. If a transformer is used, then the rectifier diodes must be capable of passing a very high peak forward current, typically 100amps or more. The 7812 IC will only pass 1 amp or less of the output current, the remainder being supplied by the outboard pass transistors. As the circuit is designed to handle loads of up to 30 amps, then six TIP2955 are wired in parallel to meet this demand. The dissipation in each power transistor is one sixth of the total load, but adequate heat sinking is still required. Maximum load current will generate maximum dissipation, so a very large heat sink is required. In considering a heat sink, it may be a good idea to look for either a fan or water cooled heat sink. In the event that the power transistors should fail, then the regulator would have to supply full load current and would fail with catastrophic results. A 1 amp fuse in the regulators output prevents a safeguard. The 400mohm load is for test purposes only and should not be included in the final circuit. A simulated performance is shown below:

source: electronics-lab.com

13.8 Volt 10 A Regulated Power Supply

2009-03-21T16:35:00.000-07:00

13.8 Volt 10 A regulated power supply. You need 10 Ampere transformer for this circuit. Complete explanation about this circuit, please visit this page.

13.8 Volt 20 A Power Supply

2009-02-10T01:36:00.000-08:00

This PSU has been especially designed for current-hungry ham radio transceivers. It delivers safely around 20Amps at 13.8V. For lower currents, a separate current limiting output, capable of 15ma up to a total of 20A has been added.

The power transformer should be capable to deliver at least 25A at 17.5 to 20V. The lower the voltage, the lower power dissipation.

The rectified current will be “ironed” by the C1, whose capacity should not be less than 40.000uF, (a golden rule of around 2000uF/A), but we recommend 50.000uF. This capacity can be built up by several smaller capacitors in parallel.

The base of this design is a simple 12V regulator (7812). The output voltage can be brought to desired value (here 13.8V) by two external resistors (R5 and R6) using this formula:

U= 12(1+R5/R6)

The low currents (here 15mA) will keep the 7812 in its regular function. As soon as the current rises over 15ma, the voltage drop on R4 will “open” the Q3, actually handling the high output current. This is a PNP transistor (Ic>25) and current amplification factor of at least 20. The one that has been tested and proven here is the 2N5683.

The current limiting resistance RL, for the maximum output of 20 Amps should be 0.03 Ohms, rated at least 15W. You can use the resistance wire or switch several resistors in parallel, totaling the resistance/power values. Values for other currents can be calculated by the rule:

RL=0.7/Imax

The RL and Q2 (3A PNP such as BD330) form a short circuit “automatic fuse”. As soon as the maximum current reaches 20Amps, the voltage drop over the resistor RL will open Q2, and thus limit the B-E Current of Q3. Parallel to Q2 is Q1, which lights the LED 1 whenever the current limiting circuit is active. When the “fuse” is active, the Q2 bridges the R3, so the full current would flow through the IC1, and damage it. Therefore the R4 is inserted, as to limit the IC1 current to 15mA. This makes it possible to run the IC1 without any cooling aid.

The LED 2 will light up every time the PSU is switched on.

There is an adjustable current limiter in parallel to the fixed output, thus providing adjustable current source for smaller currents.

This circuit is very simple too. You will notice that there is no current sensing resistor. But it is really there, in a form of the Rds-on resistance of the N-channel FET, which actually handles the load cutoff from the source. The function of the FET is shown in the diagram 2. When the current Id is rising, the tension Uds over the resistance Rds rises very slowly in the beginning, but very fast after the knick.

This means, that before the knick the FET behaves as a resistor but after it, works as constant current source.

The D2, R3 and B-E connection of the Q4 will sense the Uds voltage of the FET1. When the voltage rises enough, the Q4 will shortcut the FET1 gate to mass, and cut the current flow through the FET 1 off.

However, to enable the FET1 to open, there is certain gate voltage necessary, which in this case is brought up by the voltage divider consisting of R8, Z1, P1 and R9. So the maximum Gate voltage will be the one of the Z1, and the minimal will be around 3V6.

The Z1 voltage (Uz1) will thus determine the max current flowing through the FET 1.

The diagram 2 will show that for 5 Amps the Uz1 should be 5V6, and for 20Amps around 9V6.

The Capacitor C4 will determine the “velocity” or the reaction time of the limiter. 100 uF will make the reaction time to be around 100ms, and 1n will make it 1us.

Within the designed limits, the P1 will limit the current output in the range of 15mA to 20A.

You can use both output simultaneously, but the total output current will be limited by the value of the RL. This PSU can be built also for higher outputs, as long as the transformer will handle the current requirements, and you provide sufficient cooling for the Q3.

Current Expanded Regulated Power Supply

2009-01-25T17:19:00.000-08:00

Actually, this is ordinary regulated power supply, but the current expander using a transistor make this power supply become powerful.

Based on the datasheet, the stabilizer IC’s can deliver up to 1A output current. For example 78xx series regulators are available in different voltage ratings, but in any case the current should not exceed 1A.

The transistor Q1 (2N 29055) used here has 5A current capacity. The resistor R1 is used to keep the current through regulator IC below 300mA. When the current through R1 increases the base current of Q1 (2N 29055) also increases & the load required load current flows through this transistor. By this way a current greater than the capacity of the regulator IC can be delivered to the load. The C1 is used to filter the ripples off the rectifier output.

Notes:

Assemble the circuit on good quality PCB.
T1 can be a 230V primary,15V/1A secondary, step down transformer.
If 1 A bridge is not available, make one using four 1N 4007 diodes.
The series regulator IC should be selected according to the desired output voltage.

IC 7805 for 05V
IC 7806 for 06V
IC 7809 for 09V
IC 7812 for 12V

9V Regulated Power Supply

2009-01-21T17:45:00.000-08:00

Here is 9V Regulated Power Supply schematic diagram:

You can use this power supply for your electronics project which only require electric current about 500mA. This is cheap circuit which will give you stabilized output voltage.

If you want to change the output voltage, you should change the IC type.
For example, you need 5V output, then change the IC from 7098 with 7805 dan change the output of transformer from 16V AC become 9VAC or 12V AC.

High and Low Voltage Cutout with Delay and Music Power Supply

2009-01-17T16:41:00.000-08:00

This simple circuit will protect the costly equipment from high as well as low voltages and the voltage surges (when power resumes). It also gives a melodious tune when mains power resumes. When mains voltage is normal, the DC voltage at the cathode of zener diode D4 is less then 5.6V. As a result transistor T1 is in ‘off’ state. The DC voltage at the cathode of zener diode D5 is greater than 5.6V and as a result transistor T2 is in ‘on’ state. Consequently, relay RL1 gets energised, which is indicated by lighting up of green LED. Under high mains voltage condition, transistor T1 switches to ‘on’ state because the voltage at cathode of zener diode D4 becomes greater than 5.6V. Consequently, transistor T2 switches to ‘off’ state, making the relay to de-energise Under low mains voltage condition, transistor T1 switches to ‘off’ state and as a result transistor T2 also switches to ‘off’ state, making the relay to de-energise.

Read more explanation here

Over / Under Voltage Cut-Out Power Supply

2009-01-17T16:08:00.000-08:00

This circuit is not really simple, but will save your money :).

This over/under voltage cut-out will save your costly electrical and electronic appliances from the adverse effects of very high and very low mains voltages. The circuit features auto reset and utilises easily available components. It makes use of the comparators available inside 555 timer ICs. Supply is tapped from different points of the power supply circuit for relay and control circuit operation to achieve reliability. The circuit utilises comparator 2 for control while comparator 1 output (connected to reset pin R) is kept low by shorting pins 5 and 6 of 555 IC. The positive input pin of comparator 2 is at 1/3rd of Vcc voltage.

Read more explanation here

Low-cost 12V - 50W off-line switching power supply

2009-01-09T00:07:00.000-08:00

This is a simple low-cost 12 Volt 50W off-line switching power supply, which can be used for home projects or to learn operation of flyback converters. It can work over a universal AC line input range 90-264 VAC and provides a 12VDC output at more then 4A load. Line and load regulation is better then 0.5%. The unit has overcurrent, overtemperature and overvoltage protections as well as passive inrush current limiting. Output ripple are approximately 0.2 V. If you need to get lower ripple, you may put an additional output LC filter.

Complete explanation, visit this site

Basic Regulated Power Supply (IV)

2009-01-08T22:49:00.000-08:00

This page come from my.integritynet.com.au, will show you about how to make a variable regulated power supply.

This type of regulation is ideal for having a simple variable bench power supply. Actually I think this is quite important because one of the first projects a hobbyist should undertake is the construction of a bench supply. While a dedicated supply is quite handy e.g. 12V, it's much handier to have a variable supply on hand.

There have been many times I have had to "smoke test" a project. This means I have started out at the minimum voltage on my supply (about 3V), seen nothing untoward happening and then slowly winding up the voltage to say 15V (this would only be where the project design called for 15V).

By the way, this is the recommended way to test a project after having double checked parts placement against circuit drawings and parts placement guide (if any). Always start out at minimum voltage and look for signs of distress among components (usually resistors) THEN progressively wind up the voltage to your project voltage. Again always look for distress among your components.

Now one of the heartaches I have here is that inevitably, to derive the necessary voltage it must originate from the mains supply, either 240V or 120V A.C. I have to be mindful of the fact that many people who read my pages are VERY inexperienced. AND

ELECTRICITY KILLS.

So, if only to potentially save one life, I'm going to wimp out and stick with my original idea of using "plug packs" or also known in the US as "wall warts".

Because you are unlikely to want much in excess of 15V D.C. I have restricted my search to types of plug packs of around about 15V A.C. at something in the region of 1.25 amps. Checking through some suppliers (see below) I have found available what is available at the moment * (see below) for plug packs, meters, regulators etc.

For the purposes of this project I have nominally selected a 16V A.C. @ 1.25 Amp plug pack which comes with bare wire ends. Now you can choose to hardwire the bare ends into the case or use a plug and socket connection. You might buy something different which comes with a plug on the end - in which case buy a suitable panel mounting socket and discard my recommendation of plug and socket below.

The choice is yours but if you discount the initial bit of extra work involved, as well as about $A 1.50 extra expense ($US 1.00), I think it's nice to be able to store plug pack and case away seperately. Of course if your plug pack has it's own plug you will need a mating socket to suit.

Here is the basic circuit:

Fig 4 variable bench supply schematic

HOW IT WORKS

Now the basic theory is this. U1 is a TO-220 style variable voltage regulator (LM317T). It is a complete integrated circuit. Quoting, in part, from my old National Semiconductor handbook:

"The LM317T is an adjustable 3 terminal voltage regulator capable of supplying in excess of 1.5A over a 1.2V to 37V output range. It is exceptionally easy to use and only requires two external resistors to set the output voltage. Further, both line and load regulation are better than standard fixed regulators."
"In addition to higher performance than fixed regulators, the series offerss full overload protection available only in IC's."
FEATURES
* Adjustable output down to 1.2V
* Guaranteed 1.5A output current
* Line regulation typically 0.01%/V
* Load regulation typically 0.1%
* 80 dB ripple rejection
"An optional output capacitor can be added to improve transient response. The adjustment terminal can be bypassed to achieve very high ripple rejection ratios which are difficult to achieve with standard 3 terminal regulators".
- source National Semiconductor Linear Databook 1982 P 1-23

So there it is. A genuine "all singing, all dancing variable voltage regulator IC". All depending upon two resistors, which in our case are R1 and, the parallel combination of R2a and R2b. The maths are:

Figure 4a - Voltage out formula

Assuming we use a 5K linear potentiometer (never log or audio type) as the basis of R2 and call it R2a (real clever stuff this) AND put another resistor in parallel called R2b. For this resistor we will allow a value of 15K or 15,000 ohms. This parallel combination would at the maximum resistance setting of R2a yield a net resistance for our R2 combination (do some sums along here with me folks - do follow the leader on the calculator) of 3750 ohms.

Now for sure and certain, someone will email me and say "how for this?" Every class has it's dill. If you don't know the answer then either you took short cuts and didn't do the basics or you just plain forgot.
Either way when you do email me about this, I can virtually guarantee I will email myself back to you in return, grab you around the throat and, speak quite severely to you. Enuf said?
Worse still, I will send you a .jpg photo of myself and that has been known to terrorise small children, cause little old ladies to faint with fright and for cows' milk to sour. Don't cross me. Remember, "when all else fails read the directions"

Now back to our regular scheduled program. If we allow R1 to become 240 ohms and substituting the values into the equation above we get:

Which of course is what we set out to do. Other maximum voltages can be accomodated by simply fiddling with value of resistor R2b. There are limits and, R1 remains at 240 ohms.

Other points of interest:

1. If you want all the technical nitty gritty then download the current datasheet. I've already done the searching for you. The .pdf file is 645K. Take that or look at the online version. DON"T ask for the email version - remember we're not manufacturers' and we are imposing a little on National's goodwill - show a little netiquette.

http://www.national.com/pf/LM/LM317.html#Datasheet

2. An input bypass capacitor C2 (0.1 uf) is recommended as close as possible to the "input" terminal. Similarly, R1 should be connected as close as possible to the respective "out" and "adjust" terminals. Likewise C3 and C4 (both solid or tag tantalum) are recommended for improved performance and as close as possible to the respective terminals.

3. C1 is a recommended 2200uf / 35V electrolytic filter capacitor.

4. Diodes D1 to D4 form the bridge rectifier and are rated at 3A. Any voltage rating of 50V and up is OK but 3A is the minimum current rating. You could substitute a dedicated bridge rectifier but once over the 1A rating the next size up is !0A and becoming expensive.

5. Diodes D5 and D6 are for protection in the event either the input or output are shorted. The resistor R1 connects across the anodes of both D5 and D6 and nowhere else. Look closely at diagram. R1 does NOT connect to the "out" line. Similarly C4 connects from "output" to ground and NOWHERE else.

6. The inline ammeter and the voltmeter are optional. You can do away with either or both and substitute your digital (assuming you have one) multimeter onto or through the output terminals outside the case. Largely a question of convenience versus budget. If you use either remember to observe polarities.

7. You still have to buy a few bits and pieces not shown on the list below e.g. R1 240 ohm 1/2 watt resistor, R2b (whatever value you decide) or my 15K, and the 0.1 uF ceramic capacitor.

8. I have no connection whatsoever with the firm Jaycar I have recommended below excepting I have known the owner for over 20 years and have always personally found them very satisfactory to do business with. They have a wide number of outlets throughout Australia as well as New Zealand. As in all cases, use your own judgement. I can only comment as a satisfactory buyer.

CONSTRUCTION OF POWER SUPPLY

Obviously the power supply must have a suitable case. Size is governed by whether you include metering or not. Two side by side meters of the type recommended below, each has a face measuring 58mm(W) X 52mm (H). Then space must be allowed for the on / off switch (I recommend a DPDT type) and the red / black output binding posts. The fuse holder (essential) is mounted on the back along with the input socket. To accomodate all that you need a case of sufficient width and depth. I recommend the Jaycar Cat. HB-5446 or similar, 184(D) X 70(H) X 160(W). All dimensions in mm (inches divide by 25.4) There is a lot of drilling - so take your time.

TIP - when cutting the shaft of the potentiometer (pot) to suit the correct length, insert the shaft into a bench vise and cut with a hacksaw where you have marked it. Never wedge the pot in anything!

As I said before largely a question of convenience versus budget. If you can, try and find a suitable "U" shaped handle to fix to the top of your case in the centre, a real convenience.

Internally, mount your components on tag strips. Haunt your local parts supplier for all parts. You will also need assorted nuts, bolts and washers.

To identify the pins on the LM317T place the component on the table with the pins facing toward you. Any markings will be uppermost. The pin to your left is "adjust", Vout is the centre pin and Vin is the right most pin. The electrolytic capacitor and Tag Tantalums should have a + sign on them. See schematic diagram above - this is important. Some types of electrolytics only indicate the minus or negative pin - be careful!.

Basic Regulated Power Supply (III)

2009-01-08T14:45:00.000-08:00

Let's look at the very common LM340-X series or the equivalent 78XX series. Firstly they come in a variety of voltage ranges from 5, 12 and 15V for LM340-XX and 78XX.

They also come in a variety of current ratings and package sizes. Common packages are TO-92, TO-5, TO-220 and TO-3. The first two, TO-92 and TO-5 are generally unavailable to the hobbyist because suppliers like to keep reduced stock lines and so tend only to stock the TO-220 and TO-3 types. In fact you can pay more for a TO-92 type (rated at 100 ma) than you would for a TO-220 type (rated at 1.5A)

When you have a requirement for a project of say 12V, or even 5V if it's a digital project, then these are the types you use. LM340-5, LM340-12 or 7805 or 7812 are the types.

There are of course negative voltage regulators with the numbers LM320-XX or 79XX which are substantially the same as those discussed here excepting they are negative. We will not consider them further.

Assume your project calls for a basic fixed 12V D.C. to operate. Looking back to our earlier tutorial we apply all the same principles. Look at the original schematic.

Now the first thing I'm going to recommend for small projects, is discard everything to the left of the four diodes D1 - D4 and use a plug pack (wall wart in US). The ammeter and voltmeter I left in purely for illustration. In a normal small project you don't need them.

All we are after here is 12V D.C. @ 1A. The same principles apply to 5V. This current limit believe it or not, covers 90% of projects I have ever been involved with. Higher currents we will deal with later.

The type of regulator discussed here (LM340-12 or 7812 types) REQUIRE a minimum input voltage to function and there is a maximum they will accept. This gives you a little bit of flexibility.

In the case of the 12V regulator the minimum is 14.8V D.C. and maximum is 27V D.C. Whereas for the 5V regulator the minimum is 7.5V D.C. and maximum is 20V D.C. Please note these are DC voltages.

Also note if you use plugpacks, you can choose to buy the D.C. types and dispense with the diodes. If A.C. is all that is available then the diodes MUST go in. As is the case with many things it all depends upon what you can buy in your locality.

Just remember to buy a plug pack which will deliver at least the minimum required input voltage at your current requirement (don't buy without first scrounging around your relatives, friends and neighbours - recent statistics must surely indicate there are more plug packs around than there are people on this earth).

Hokay!, I just found a 15V D.C plug pack capable of 1A. Suits me fine for my project. I also have on hand a 4700uF / 25V electrolytic capacitor, this is also fine and I have a LM340-12 regulator of the TO-220 type as well. Here is how I connect it

Now here C1 is our electrolytic capacitor while C2 and C3 are cheap ceramics at 0.22 uF and 0.1 uF respectively. Simple eh! A decent heatsink needs to be connected to the IC because if you are drawing appreciable current AND your input voltage is getting higher then the IC starts to dissipate a fair bit of power.

Note: the pin connections for an LM340T12 when placed face up on the bench with the pins toward you, are left pin = input, middle pin = ground and, right pin = output. Always check pin outs of all devices you buy. In this case, the tab (top of IC with hole in it) is at ground potential. Unfortunately many other regulator IC's aren't.

F1 is a fuse and should be about twice the expected current to be drawn at 12V. The switch might be optional depending on whether or not you are going to switch on / off at the power point. The socket depicted is a panel mount type to suit the plug pack plug, you could dispense with that by bringing wires directly into project box but then your plug pack can't be used for something else! ALSO PAY CLOSE ATTENTION TO POLARITY.

HIGHER CURRENT SUPPLIES

Well how high is high? If you believe my email some people want 13.8V D.C. @ 50 A !!!!

I'm NOT going to get into that because there are more problems here than there are in a can of red backs (black widows). Doing an exotic design, without actually building and testing it, is somewhat dopey to say the least and; as I don't have such a requirement I'm not about to spend the money on it (megabucks to say the least - and largely forget surplus computer power supplies because they create other problems).

If you wanted say 3 amps then look at something like a LM350 type regulator (consult the appropriate data sheet) which also is happily; adjustable (just like the LM317 in Part 4 next). Diodes have to have a suitable rating of course and you won't get a plug pack at 3 amps so it's back to transformers which:

FOR SAFETY REASONS WITH INEXPERIENCED READERS I WILL NOT RECOMMEND

I don't have any control over my readers so I won't discuss the transformer input half at all. You will have to make your own arrangements. If you are experienced no problem, if not then find someone competent to help you out.

EVEN HIGHER CURRENT

This is straight from a National Semiconductor data sheet, will supply a variable voltage (1.2V - 25V and up to 10A) I will assume you obviously have available a source of D.C. voltage (filtered) @ 10A.

Here is the broad schematic BUT you will have to consult the LM350K data sheet AND applicaion notes.

Down load the data sheet: http://www.national.com/pf/LM/LM350.html#Datasheet

Now if you are competent to build a 4.5V to 25V variable power supply capable of supplying 10 amps then the above information is all you need. On the other hand if the above leaves more questions than were answered then obviously you need more experience. The little schematic above, as a project, would run into hundreds of dollars to build. For experience, try the smaller project in the next section. It's a useful tool.

source: http://my.integritynet.com.au/purdic/power3.htm

Basic Regulated Power Supply (II)

2009-01-08T04:02:00.000-08:00

To regulate small amounts of current the cheapest approach is to use a zener diode. Higher currents can be obtained from higher power zeners but I prefer to use dedicated I.C.'s in these cases. In one instance you can use a zener diode in conjunction with a pass transistor to extend the range of the zener regulator.

As with our previous design example in Part - 1 we had a small unregulated bench supply of 500 ma for our projects. Now we have decided that it should become a well regulated, well filtered supply giving us 13V dc.

By using a series pass transistor we are extending the useful range of the zener diode as well as reducing Vo ripple. This is called "electronic filtering".

There is one large handicap with this circuit though. Under over-current conditions Q1 will most likely be destroyed long before F1 blows. Of course I have very cynical (practical?) friends who will tell you that if you buy up Q1 types at 5c each then in fact they are cheaper than most fuses anyway. Q1 usually requires a suitable heatsink.

FACT: Back in the olden days when transistors first emerged (and were incredibly expensive believe me) valve enthusiasts, (code for non-transistor literate) described transistors as "the dearest, but fastest acting fuse so far devised by man."

Most calculations you will note are still in accordance with the example in Part 1.

To calculate the value of Rs in the above figure you need to know the base current I_bfor Q1. This is the emitter current I_e divided by the transistor beta. It is preferable to meaure the transistor beta if you can (some meters have this facility) because the spread of beta on most transistors, even from the same batch, is about as wide as Sydney Harbour.

For the purposes of this exercise we will use the general purpose but cheap 2N3055 which will be mounted on a heat sink. Our beta measured 34. (if in doubt use mfrs. minimum beta from data sheet). Our base current is the emitter current divided by beta.
In this case we have 500ma/34 or 14.7ma. Also for decent regulation ZD1 needs a fair amount of current. I would suggest something about 25ma. Armed with this information, if Iz = 25ma minus the earlier Ib of 14.7ma = 10.3ma and if our dc voltage at C1 is 25.3V and our zener is 14V then Rs = [25.3V - 14V]/0.0103 = 1097 . I would use 1K

The power rating of both the zener and Rs are calculated as follows:
ZENER P_d = [ ( V_in - V_z) / Rs] X Vz = [ ( 25.3 - 14) / 1000 ] X 14 = 0.16W
It is quite common to use a safety factor of 5 so I would opt for a 1W type zener.

Rs P_d = ( V_inmax - V_z )² / Rs = ( 25.3 - 14 )² / 1000 = 0.128W (use a 1/2 watt resistor).

CURRENT LIMITING - I have decided it is pointless including design for additional circuits for current limiting as this is provided even more economically with dedicated IC's. In fact all of the foregoing is mainly to give you the general basics.

source: http://my.integritynet.com.au/purdic/power2.html

Basic Regulated Power Supply

2009-01-08T03:44:00.000-08:00

The ac from the transformer secondary is rectified by a bridge rectifier D1 to D4 which may also be a block rectifier such as WO4 or even four individual diodes such as 1N4004 types. (see later re rectifier ratings).

The principal advantage of a bridge rectifier is you do not need a centre tap on the secondary of the transformer. A further but significant advantage is that the ripple frequency at the output is twice the line frequency (i.e. 50 Hz or 60 Hz) and makes filtering somewhat easier.

As a design example consider we wanted a small unregulated bench supply for our projects. Here we will go for a voltage of about 12 - 13V at a maximum output current (I_L) of 500ma (0.5A). Maximum ripple will be 2.5% and load regulation is 5%.

Now the rms secondary voltage (primary is whatever is consistent with your area) for our power transformer T1 must be our desired output Vo PLUS the voltage drops across D2 and D4 ( 2 * 0.7V) divided by 1.414.

This means that Vsec = [13V + 1.4V] / 1.414 which equals about 10.2V. Depending on the VA rating of your transformer, the secondary voltage will vary considerably in accordance with the applied load. The secondary voltage on a transformer advertised as say 20VA will be much greater if the secondary is only lightly loaded.

If we accept the 2.5% ripple as adequate for our purposes then at 13V this becomes 13 * 0.025 = 0.325 Vrms. The peak to peak value is 2.828 times this value. Vrip = 0.325V X 2.828 = 0.92 V and this value is required to calculate the value of C1. Also required for this calculation is the time interval for charging pulses. If you are on a 60Hz system it it 1/ (2 * 60 ) = 0.008333 which is 8.33 milliseconds. For a 50Hz system it is 0.01 sec or 10 milliseconds.

The formula for C1 is:

C1 (uF) = [ ( I_L * t ) / Vrip ] X 10⁶
C1 = [ ( 0.5A X 0.00833 ) / 0.92V ] X 10⁶
C1 = 0.00453 X 10⁶ = 4529 or 4700 uF

Remember the tolerance of the type of capacitor used here is very loose. The important thing to be aware of is the voltage rating should be at least 13V X 1.414 or 18.33. Here you would use at least the standard 25V or higher (absolutely not 16V).

With our rectifier diodes or bridge they should have a PIV rating of 2.828 times the Vsec or at least 29V. Don't search for this rating because it doesn't exist. Use the next highest standard or even higher. The current rating should be at least twice the load current maximum i.e. 2 X 0.5A or 1A. A good type to use would be 1N4004, 1N4006 or 1N4008 types. These are rated 1 Amp at 400PIV, 600PIV and 1000PIV respectively. Always be on the lookout for the higher voltage ones when they are on special.

TRANSFORMER RATING - In our example above we were taking 0.5A out of the Vsec of 10V. The VA required is 10 X 0.5A = 5VA. This is a small PCB mount transformer available in Australia and probably elsewhere. This would be an absolute minimum and if you anticipated drawing the maximum current all the time then go to a higher VA rating.

source: http://my.integritynet.com.au/purdic/power1.html

12V / 20 mA max Transformerless Power Supply (input 230V)

2009-01-06T17:38:00.000-08:00

If you are not experienced in dealing with it, then leave this project alone. Although Mains equipment can itself consume a lot of current, the circuits we build to control it, usually only require a few milliamps. Yet the low voltage power supply is frequently the largest part of the construction and a sizeable portion of the cost.

This circuit will supply up to about 20ma at 12 volts. It uses capacitive reactance instead of resistance; and it doesn't generate very much heat.The circuit draws about 30ma AC. Always use a fuse and/or a fusible resistor to be on the safe side. The values given are only a guide. There should be more than enough power available for timers, light operated switches, temperature controllers etc, provided that you use an optical isolator as your circuit's output device. (E.g. MOC 3010/3020) If a relay is unavoidable, use one with a mains voltage coil and switch the coil using the optical isolator. C1 should be of the 'suppressor type'; made to be connected directly across the incoming Mains Supply. They are generally covered with the logos of several different Safety Standards Authorities. If you need more current, use a larger value capacitor; or put two in parallel; but be careful of what you are doing to the Watts. The low voltage 'AC' is supplied by ZD1 and ZD2. The bridge rectifier can be any of the small 'Round', 'In-line', or 'DIL' types; or you could use four separate diodes. If you want to, you can replace R2 and ZD3 with a 78 Series regulator. The full sized ones will work; but if space is tight, there are some small 100ma versions available in TO 92 type cases. They look like a BC 547. It is also worth noting that many small circuits will work with an unregulated supply. You can, of course, alter any or all of the Zenner diodes in order to produce a different output voltage. As for the mains voltage, the suggestion regarding the 110v version is just that, a suggestion. I haven't built it, so be prepared to experiment a little.

I get a lot of emails asking if this power supply can be modified to provide currents of anything up to 50 amps. It cannot. The circuit was designed to provide a cheap compact power supply for Cmos logic circuits that require only a few milliamps. The logic circuits were then used to control mains equipment (fans, lights, heaters etc.) through an optically isolated triac. If more than 20mA is required it is possible to increase C1 to 0.68uF or 1uF and thus obtain a current of up to about 40mA. But 'suppressor type' capacitors are relatively big and more expensive than regular capacitors; and increasing the current means that higher wattage resistors and zener diodes are required. If you try to produce more than about 40mA the circuit will no longer be cheap and compact, and it simply makes more sense to use a transformer.

Important Notice:
Electric Shock Hazard. In the UK,the neutral wire is connected to earth at the power station. If you touch the "Live" wire, then depending on how well earthed you are, you form a conductive path between Live and Neutral. DO NOT TOUCH the output of this power supply. Whilst the output of this circuit sits innocently at 12V with respect to (wrt) the other terminal, it is also 12V above earth potential. Should a component fail then either terminal will become a potential shock hazard.

source: www.zen22142.zen.co.uk

5V / 100mA max Transformetless Power Supply (input: 110V AC)

2009-01-06T16:15:00.001-08:00

This is transformerless power supply schematic diagram. Please take a note that this circuit running ONLY for input voltage 110V AC.

I use this power supply for applications that doesn't use too mucho power. It can provide power to circuit that uses less than 100mA without any problem. The disadvantage of this circuit is the danger of an electrical shock, so it cannot be used if the circuit is in contact with the user.

The voltage supplied by this is determined by the zener diode.

The version of the transformerless power supply that uses a bridge rectifier provides more current than the first one because it rectifies both phases of the AC voltage.

Unregulated Power Supply

2009-01-06T07:46:00.000-08:00

This is a very basic AC to DC rectifier power supply. The transformer is chosen according to the desired load. For example, if the load requires 12V at 1amp current, then a 12V, 1 amp rated transformer would do. However, when designing power supplies or most electronic circuits, you should always plan for a worst case scenario. With this in mind, for a load current of 1 amp a wise choice would be a transformer with a secondary current rating of 1.5 amp or even 2 amps. Allowing for a load of 50% higher than the needed value is a good rule of thumb. The primary winding is always matched to the value of the local electricity supply.

Notes:
An approximate formula for determining the amount of ripple on an unregulated supply is:

where I load is the DC current measured through the load in amps and C is the value of the capacitor in uF.The diagram below shows an example with a load current of 0.1 amp and a smoothing capacitor value of 1000uF.

The calculated value of ripple is (0.1 * 0.007) / 1000e-6 = 0.7 volts or 700mV. The value of peak-peak ripple measured from the graph is 628mV. Therefor, the equation is a good rule of thumb guide for choosing the correct value for a smoothing capacitor in a power supply.

source: http://www.zen22142.zen.co.uk/Circuits/Power/unreg.htm