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# Need help powering two circuits on a single power supply Answered

Hello, I need some help with a project I'm working on and hopefully someone has an answer. I'm building a white noise generator  and it consists of two circuits, the white noise generator and a amplifier. Now when I bread boarded these I had each circuit built on its own bread board powered by its own 9v battery supply, but I want to have both circuits powered by a single 9v power supply with a 5v voltage regulator.
Now when I bread boarded the device it worked fine using two 9v batteries powering the individual circuits, but when I connect them to a single power supply the circuit starts oscillating instead of generating white noise.  I've tried all sorts of different ways of rewiring the circuit, but I can't get it to run on a single 9v source without it oscillating. I think it has something to do with the amplifier signal feeding back into the white noise circuit. What I can't figure out is why it works when powered by two separate power sources and not a single power source.
Anyone have an idea of what's going on here? I could really use some advice.

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## 4 Replies

supernoodle2014 (author)2016-05-24

Are you using a 9v wall adapter? if so the problem is hard to explain. The answer would be to get two .1uf Capacitors and one 100uf Capacitor. put one .1uf and the 100uf Capacitors on the Vin of the 5 Regulator with the polarity correct. then put the other .1uf capacitor on the Vout of the Regulator. You need to do this because the wall adapter is changing AC to DC, AC is pulsating at 60herts (at least in the U.S.), and the DC current is pulsating because of it. The Capacitors should clean that up so you get a steady stream of DC electricity. hope this helps explain it.

DoomG (author)2016-05-20

My best guess is that electricity follows the path of least resistance. If this is true to the circuit, the power will follow only one path in the circuit. My guess is that it has to be routed in parallel. I am having the same trouble on my PWM DC Motor Control Access Terminal.

steveastrouk (author)2014-04-21

Yeah, you have a ground loop issue. Post your circuit, and some pictures of the build