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make a bi-polar dc supply from two un-regulated supplies

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metaldefektor

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I am wondering if there is any way possible to make a(1) bi-polar 9v dc supply from 2 9v dc wall-warts. I was thinking of one 9v supply running the positive supply and one 9v running the negative supply. Would the two unused wires be able to go to a couple of capacitors in series to form the ground or virtual ground?
Also I was assuming that common wall-wart supplies of either polarity were un-regulated but I wasn't quite sure of that.
 

Simply connect the outputs of the wall-warts in series like you would with batteries. Then you have +9V, 0V (where they are joined together) and -9V.
Yes, most wall-warts are not regulated. I have a little 9VDC wall-wart that is 9VDC with noticeable ripple at its rated current but is almost 18VDC with no load.
 

Strictly speaking, the extra capacitors are not needed to have a common mid-point ground, although the extra filtering is welcome for most applications. The tie point where the -ve of one wall wart and the +ve of the other wall wart are connected together is ready to be used as the common ground.
 

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