Dual Adjustable Power Supply

Rajkumar Sharma      http://www.rajkumarsharma.com  
Project tested


This project is a solution to power up most of devices or projects requiring dual (+/-) adjustable power supply.


The circuit is based on LM317 positive and LM337 negative voltage regulators. LM317 series of adjustable 3 terminal regulator is capable of supplying in excess of 1.5A over a  1.2V to 30V DC output range, due to TO3 package of  IC and large heat sink the power supply can handle maximum load  current.

  • Output: +/- 1.2 to 30V DC
  • Output Current: 1.5Amps
  • Supply Input: 24V-0-24V AC, 2Amps Center tape Transformer
  • CN1: Transformer Connections
  • CN3: +/- Dual Supply Outputs
  • P1: Positive Voltage Adjust
  • P2: Negative Voltage Adjust
  • D1: Positive Power Indicator
  • D2: Negative Power Indicator



Parts List




19 Response on “Dual Adjustable Power Supply

  1. Can I use this two 220VAC/12VAC halogen transformer serial connected?
    If they have 12VAC 60W output each, I should get 24VAC 120W 5A output.
    Or this one :
    Connected directly to the output of the diode bridge.
    Which one is the best option?

  2. what would be the output voltage range if i only used a 15 – 0 – 15 transformer? thank you. great work by the way, neat and nice.

    1. With a 15Vac transformer you will get around 21V peak voltage, minus the voltage drop in rectifier and regulator you will get around 16-17V at the output.

  3. I used 24-0-24V, 1Amp Transformer as i needed max 1 Amp. The problem with the circuit is, without any load connected o/p is 1.5V to ~33V at positive side and the same with negative side ( obviously with -ve values). (after measuring on multi-meter) But, as i connect any load the +ve side provides stable and proper voltage supply. However, on -ve side it just stuck around 1.5V to 3V. I checked for any short circuits, bypass capacitors, etc. And every thing is seems good. But, only at pin’s of LM337 might be problem . so, i tried with LM905 and the same thing happens with it. no voltage at output when load is connected.
    Please, let me know what’s happening? and how to make corrections?
    Thanks in Advance…

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