mixing DC power supplies

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perfectbite
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mixing DC power supplies

Post by perfectbite » Fri Apr 09, 2004 9:41 am

I do not have a 17VDC power supply but I do have individual 5VDC and 12VDC power supplies each with a different but above 2Amp rating and I need 17 volts for a stepper motor test. My humble question to you all is 'Can I series the different power supply outputs to get 17VDC without smoking either power supply?' Thanks.

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Dave Dixon
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Re: mixing DC power supplies

Post by Dave Dixon » Fri Apr 09, 2004 11:06 am

Probably - - BUT - - First you need to be sure that both power supply returns (-) are isolated. Have them each plugged in and turned on and check for continuity between the two power supply returns. If there is no continuity - you are in business. Most good power supplies have the return (-) isolated from case/line ground, but not all.
Good luck,
Dave

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Dave Dixon
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Re: mixing DC power supplies

Post by Dave Dixon » Fri Apr 09, 2004 11:12 am

On another note, how about two nine volt batteries = 18V. If you have to have 17 use a diode or two as discussed in the thread "Voltage drop across silicon diode"
Dave

perfectbite
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Re: mixing DC power supplies

Post by perfectbite » Sat Apr 10, 2004 9:31 am

Thank you Dave, that worked. I did think of using 9V batts but my original problem (the one I wanted to check) may have been a lack of amperage to begin with, it wasn't. Stepper notors may be strong but I found, much to my disappointment, that if the load doesn't move on the first pulse it ain't gonna move on the umpteenth pulse (it wasn't much of a load either and steppers aren't gravity friendly, even very light vertical loads tend to fall back down). Meanwhile, back at the drawing board, one door closes another opens.

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Chris Smith
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Re: mixing DC power supplies

Post by Chris Smith » Sat Apr 10, 2004 10:55 am

Dont forget that its only as strong [amperage] as the lowest number out put value of any multiple PS. Same goes for batteries, its only as strong [amperage]as the weakest battery.

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