Ron Broberg/Projects/Variable Voltage Regulator

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This variable voltage supply is built on the LM317 variable voltage regulator integrated circuit. It is based on one by van Roon. The left hand circuit in TvR's original can be replaced with an ATX computer power supply. The right hand circuit in TvR's original was replaced by a handheld voltmeter. This variable voltage regulator supplies 1.2VDC - 32VDC at about 1.5 amps.


Overhead view of the power supply.

Left hand view of the power supply.

Right hand view of the power supply.

Front-right view of the power supply in operation.

Bill of materials

Power supply (in)

  • BR1 = Bridge Rectifier
  • TR1 = Transformer 24VAC, 3A
  • S1 = On-Off toggle switch
  • Fuse = 115V, 500mA, slow-blow
  • FuseHolder, enclosure, knob for P1
  • Plug = 3-wire plug & cord

Voltage Regulator

  • IC1 = LM317, adjustable regulator
  • D1 = 1N4001
  • C1 = 1000uF/63V, electrolytic (see text)
  • C2 = 0.1uF (100nF), ceramic
  • C3 = 1uF/40V, electrolytic
  • R1 = 22K (18K in orig)
  • R2 = 220 ohm
  • R3 = 27K
  • Led1 = Led of your choice
  • P1 = 5K, potentiometer
  • Red and Black Banana Jacks, coolrib for IC1.

Voltmeter (Not used)

  • V = Meter, 30V, Ri = 85 ohm
  • P2 = 10K, Bourns trim-pot