The Ultimate Prototyper's Varible Output Power Supply

Do you need a variable power supply but don't have the space or budget for the expensive benchtop models? The Ultimate Prototyper's Variable Output Power Supply will provide up to 1.5A of regulated DC current at any voltage between 1.2V to your input voltage (max 12V). Use for field testing of an analog amplifier or just to see how bright that LED shines.

Warning: Due to the bare electrical connections on the power supply, do not use the power supply on a conductive surface or near conductive objects such as metal tools. For protection, it is advised that you cover the assembly in electrical or duct tape to prevent shorts that may cause batteries to overheat. If you notice any component becoming very hot or smoke, remove the batteries immediately and turn the power supply off.


HIGHVOLTAGE (Jul 26, 2014)
how did you get 12V out of a 9V battery? did you use a capacitor or something?
npol1 (May 18, 2013)

Regarding concerns about adequate heat dissipation, current, and voltage capabilities: Testing the power supply in a typical environment under 5 different resistive loads through 28 different trials showed no problems regarding heat dissipation for loads greater than 47 ohms--appropriate for most simple circuits except motors. Even at 47 ohms, the maximum temperature was approximately 35*C, not enough to cause burns. A chart will be posted soon showing the results. Voltage ranges observed were 1.9 to 11V. Maximum current draw was 200mA due to test equipment limitations.

200AQWH (May 09, 2013)

Better heat sink the 317 regulator if you intend to draw any significant current with a large input to output voltage difference. The 317 has over temperature thermal shut down but it will burn your finger long before the thermal shut down kicks in. Power dissipated in the chip will be approximately P=IV=I(Vin-Vout). Ouch!

npol1 (May 09, 2013)

Yes, although the potentiometer case can act as a heatsink, for anything other than a few milliamps for IC's, you would need a proper heatsink. It's a prototyper's power supply--customize it to meet your needs.

DrDigit (May 09, 2013)

there is also a 1.7(20ma) volt to 2.5volt(1.5A) drop-out voltage specification on this regulator which needs to be accounted for. Typically this suggests that you would need this additional voltage at the input to maintain the regulation at the output.

npol1 (May 09, 2013)

This is why I specify the 1.2V minimum output requirement. It's not desirable, but good enough for voltages you cannot get using a battery. For anything more advanced, you should get a good multi-output power supply, something better than a hacked PC one because they break with certain loads.

ADRIAN (May 09, 2013)

I would like to know how you intend to get 1.5A out of a 9 Volt PP3 battery? Referance: This shows a MAX current of 400Ma for Carbon/Zink and 565 Ma from an Alkaline type. Yes "Lithium" will go 1200 Ma or 1.2 Amps but the cost would be to high for use.

npol1 (May 09, 2013)

The 9V connector is simply there as a plug so you don't have to solder leads to a battery pack each time. You can get battery packs that work with the 9V plug but are not for a 9V battery. In particular: 2128083 for 4AA 6V 216267 or 216259 for 8AA 12V Or just solder a '9V' connector to your own battery pack.