tindle@ms.uky.edu (Ken Tindle) (02/01/90)
I posted here a short while back with a problem in a microprocessor- controlled audio project. I received some help from several people, and have the problem fixed. For reference, I was using two power supplies in the project to keep digital switching noise out of the audio, but had noise anyway. The digital side was being driven by a TI 99/4A supply, and this was the problem. Not that it was sub-par per se, it just wasn't designed for the use I needed. All +12 volts is not created equal! The five volt output was clean, but the +12 didn't like to give me the LED multiplex current pulses I needed, and made a noisy ground plane. Switching to optoisolators driven by the TI +5 with a constant-current o-c circuit, and a small separate six volt supply with an isolated ground cleared this mess up. Thought I'd post this to tell folks to watch these small switching power chassis with multiple outputs; sometimes they bite! --------------------------\ /----------------------------------------------- INTERNET:tindle@ms.uky.edu | "Could you please continue the petty bickering? BITNET: tindle@ukma.bitnet | I find it most intriguing." --- Data, Ken Tindle - Lexington, KY | Star Trek, The Next Generation, "Haven" --------------------------/ \-----------------------------------------------