Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ukma!tindle
From: tindle@ms.uky.edu (Ken Tindle)
Newsgroups: sci.electronics
Subject: Multiplex noise
Message-ID: <13647@s.ms.uky.edu>
Date: 10 Jan 90 21:49:46 GMT
Reply-To: tindle@ms.uky.edu (Ken Tindle)
Distribution: na
Organization: U of Kentucky, Mathematical Sciences
Lines: 25

I have a problem that has me thrown for a loop-

I've got a project running digital and audio side-by-side, which I've always
known was trouble; it's fun keeping the audio clean.

So I have three power supplies- +12 for audio; +12 for 60 multiplexed LED's;
and +5 for microcontroller power.

My problem is a whine in the audio, caused by the LED's turning on and off.
All these supplies are separate from each other; I did this to (ha) keep the
audio quiet.

The digital and LED power is coming from a new, surplus TI 99-4A board.  Is
this thing known to be unstable, when drawing current pulses out of it's +12
output?  It should be providing me with some isolation, but using the audio
+12 for everything actually works slightly better!

The audio power supply (a Lambda LSS series 25W) and the TI supply have a 
common ground- am I gonna have to separate them?

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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"
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