Variable Power Supply Circuit 6-12V

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

Variable Power Supply Circuit 6-12V

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)


  • 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.

About Power Supply
A power supply is a device that supplies electrical energy to one or more electric loads. The term of "power supply" is most commonly applied to devices that convert one form of electrical energy to another, though it may also refer to devices that convert another form of energy (e.g., mechanical, chemical, solar) to electrical energy.
A power supply may be implemented as a discrete, stand-alone device or as an integral device that is hardwired to its load. In the latter case, for example, low voltage DC power supplies are commonly integrated with their loads in devices such as computers and household electronics. More explanation about power supply can be found at

This is the tutorial about "How to build an AC to DC power supply ". The video tutorial covers the basics of diodes, bridge rectifiers, and how to build simple unregulated AC to DC power supplies than can handle a few mA up to several Amps.

Watch the video: