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[DPRG] Power question

Subject: [DPRG] Power question
From: ed at okerson.com ed at okerson.com
Date: Sun Jan 31 21:11:23 CST 2010

In electronics voltages are measured relative to reference level called
"ground".  That is why there are always at least two leads from a power
supply.  But ground is not always the lowest voltage present in a circuit.
 Think if you create a circuit with two 9v batteries in series, and call
the junction between the batteries ground, now you will have +9v, ground
and -9v.

Ed Okerson

> OK-
> I need a 5v power supply for a project. I get that. What I don't get is
> "-5 v". Where can I go to learn more about that? I'm not sure that's a
> concern for me yet, but in looking at switched power supplies (I get the
> switched part), I find +5v, 12v, -5v. Free me from my ignorance, master,
> so that one day I may snatch the pebble from your hand.
> Sincerely, Grasshopper
> Bruce K. Harlan
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