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# Help with a DIY 90vdc power supply with low amps from a 120vac standard line. Answered

I need to make a power supply for a project. I need 90vdc with very low amperage. I am currently using (10) 9v batteries placed in series to get 90volts. I would like to make a custom power supply so I can get 90vdc from a standard 120v AC power line. Preferably I'd like something I could make and put on a circuit board. Thanks!

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So...Re-design has a good solution to get your power, but what on earth are you building that needs 90v? Is there any different more 'common' options?

It's called a nothing box, it was something that was built 40 to 60 years ago. It's a series of NE/2 Neon bulbs in a something the size of half a shoe box there are 9 bulbs that flash randomly due to a spider web of capacitors and resistors. The NE/2 bulbs flash at 90volts of dc current for just about 50ms. They blink randomly every second, it use to run on two 45vdc radio batteries that either are prohibitively expensive or hard to find. I'd like to make a plug and play option to run these bulbs rather than relying on batteries.

Definitely consider steve's idea of using a 12vac wall wart with a couple voltage doublers.

If you are only using a VERY low current, and can get away with ripple, I'd use a 12V transformer and double it, to ensure you only have a small current available.

Thanks for the reply. Yes, I only need very small current, less than one amp probably less than 500ma, most likely less than that. What do you mean when you say double a transformer?

I meant really low, like 10s of mA or less
"Doubler"
Look for "voltage doubler" circuits - take an AC source, pass it through a doubler, get twice the volts at half the amps. Do it 3 x in your case, and 12V becomes 96.

Steve

Take two 12 volt transformers and connect the 12 volt secondaries together. Put a plug, switch and fuse on the primary of the first transformer. Now when you plug it in you will get approx 110 volts a/c on the other primary line. You can put a high volt diode on this and get approx. 110 d/c. You can calculate the proper resistor to get this down to 90 volts. Add a 150 volt capacitor and you can get fairly clean d/c at 90 volts out of the.

BUT!!!!

This can be very deadly if you aren't careful and insulate all exposed connections and put in a metal box and ground the box etc, etc, etc.

Thanks for the quick reply. I might give that a shot, it makes me a little wary to deal with something that can be quite dangerous. But I like your style. Thanks.