dual purpose power supply

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#1 dual purpose power supply

Post by ed »

I'm a bit out of my depth here, so I thought I'd shout help.....

At present I have generated a balanced supply for the sig gen from a dual winding Tx in the time honoured fashion using 1 bridge and a pos and neg voltage regulator.....I can then supply an op amp with the balanced voltage and take a seperate supply off the pos rail for a 7805 for the processor...whole thing has a common ground...I don't have a problem understanding this....

but I thought I'd get clever and intro a splitter so I can dispense with the Tx and use a wall wart at twice the rail voltage. Problem I have in my head is that the splitter has a floating ground and I have lifted the actual splitter ground by 10R to make a virtual ground...If I then connect 7805 to the supply for a seperate processor supply I'm compromising the splitter ground...I think..because the source negative(gnd for the 7805) is not the gnd for the splitter.

trixy to explain...I will follow up with a drawing....

I could take the 7805 from the pos rail of the splitter but I'd have less headroom for the 7805 itself...
I think I've answered my own question.....must be having one of those days.....I'll just make the supply an 18v smps and take 5v reg from the positive 9v rail....the whole thing can float...

I suppose I could delete the thread ... but it's good to talk, even if it exposes me as a fool.
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Mike H
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#2 Re: dual purpose power supply

Post by Mike H »

Had to go over that several times, but yeah, I think so. Main thing is your splitter transistors need to sink any unequal current so the centre tap doesn't drift.
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