- #1
madhatter4
- 4
- 0
Hello all,
I made a custom power supply using a standard ATX computer PSU. I took the -12V and +12V leads to get 24V then put a LM338 on the positive side for a 1.25V to 22V adjustable ouput. Works great.
I wanted to put a digital voltmeter on the adjustable output so I would know what voltage was being supplied at the banana terminals. I bought an LED digital panel meter from ebay and wired the voltmeter supply to +5 and ground from my moded ATX PSU. When I connect the adjustable +12V and -12V leads from my PSU to the sense leads on the voltmeter my PSU shuts off. I am guessing its because of a short caused by the negative sense lead and the supply ground being connected somewhere in the voltmeter PCB. If I only connect the + lead from the adjustable output to the voltmeter I get a reading of about half what I should as its only measuring from the + side of the adjustable output.
Is there a simple way to either isolate the voltmeter power or trick the meter into thinking it is seeing an additional +12V? Would adjusting the Vref on the voltmeter do the trick?
Thanks for any help you can offer.
I made a custom power supply using a standard ATX computer PSU. I took the -12V and +12V leads to get 24V then put a LM338 on the positive side for a 1.25V to 22V adjustable ouput. Works great.
I wanted to put a digital voltmeter on the adjustable output so I would know what voltage was being supplied at the banana terminals. I bought an LED digital panel meter from ebay and wired the voltmeter supply to +5 and ground from my moded ATX PSU. When I connect the adjustable +12V and -12V leads from my PSU to the sense leads on the voltmeter my PSU shuts off. I am guessing its because of a short caused by the negative sense lead and the supply ground being connected somewhere in the voltmeter PCB. If I only connect the + lead from the adjustable output to the voltmeter I get a reading of about half what I should as its only measuring from the + side of the adjustable output.
Is there a simple way to either isolate the voltmeter power or trick the meter into thinking it is seeing an additional +12V? Would adjusting the Vref on the voltmeter do the trick?
Thanks for any help you can offer.