| chipco3434 |
What causes an uneven voltage output on a +/- supply...
This should be a no-brainer but I have tranny of 30VAC and voltage of 40VDC. No problem. But it is +5VDC to GND and -35VDC to GND.
Tranny to bridge then to a couple rows of caps. GND comes from AC GNC "down the middle of the caps... |
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| paulb |
GND has to come from a source of some kind, the capacitors do not work well as a voltage divider as you have found. It should go to the centre tap of your transformer. If you have none, you would have to do something like a voltage doubler arrangement or a supply splitter circuit afterwards.
How much current do you need this supply to provide? |
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| chipco3434 |
I have no center tap...
Ah ha!
But I have made this 30VAC from two transformers of 15VAC... I guess I ought to connect the GND to the point where I connected the two trannys. Right?
Anyway, it would be nice to know the alternative.
A couple or three amps I reckon...
That would be plenty.
Thanks for the physics lesson! |
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| chipco3434 |
From where the two transformers are connected, I ran a wire to ground. DC voltage is now +20 and -32 after the caps and snubbers.
What gives? |
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| pinkmouse |
| Are the transformers identical? Have you measured with a load on the PSU? |
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| chipco3434 |
| No, I haven't applied a load. The measurements are unloaded. 1K 2 watt OK? To each side and GND and then test + to -? |
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| chipco3434 |
It works with a load. Each side with a R390 2 w and the voltage is ~20 on each side... within a few mV,
How come? |
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| chipco3434 |
"We" as in "scientists, physicists and hobbyists"?
Cool. |
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| SY |
| "We" as in people who don't have the stuff in front of us so we can nail down the reason. |
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| apolon34 |
you should use a separate diode bridge for each transformer and then tie together the + output of one bridge with - ouput of the other. This'll be your gnd point.
il your transformers ac voltage are the same, the dc will be the same too. |
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