Another simple project that you are gonna need it if you’re starting out in electronics. This was my first workbench power supply and I still use it.It will suit your needs for most of your bench testing and prototype applications. No more batteries and wires stacked together. The output is adjustable from 1.2 volts to about 30 volts.

Maximum current is about 1.5 amps which is also sufficient for most of your projects. It is easy to build and can be pretty cheap if you have some of the required parts.Be sure to put a cooling rib on IC1, at its max 1.5 A current it quickly becomes very hot.Most of the parts are obtainable at your local electronic parts shop.Whatever type transformer you get or purchase, make sure it does not exceed 24VAC. The LM317’s max input voltage is 36V. 24VAC x 1.44pp = 34.56Vdc so right at the maximum edge.

Better to obtain a transformer with a little less voltage and be safe. An 18VAC transformer will still give you about 26VDC and more then anyone hobbyist ever need.The amperage of the transformer should be 3A or so. That way it does not get hot.You can use a small case to fit the circuit and the transformer inside, make sure it has some ventilation holes. The LED will remain lit after switching off the power and slowly bleeds off via electrolytic capacitor C1, this is normal. You should follow all the safety precautions when working with mains voltage. Insulate all connections on the transformer.

VARIABLE POWER SUPPLY

Parts List:

  • BR1: Bridge Rectifier 30 v 5 A
  • R1: 18k
  • R2: 220 R
  • C1: 2200 uF
  • C2: 0,1 uF
  • C3: 10 uf
  • LED: 1 led the color of your choice
  • IC1: LM317 adjustable regulator
  • P1: 5K potentiometer
  • D1: 1n4001