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# How To Get 250vdc at 1.5a from our Variac

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We

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Those are lethal voltages & currents. Very bad idea for a Science Fair project.

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Blueroomelectronics:

We are not idiots - we took 4th place at the international fair last year with our hydrogen generation. If you can't help then please don't criticize us.

Lonnie Tyre

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He's probably right though, normally lethal voltages at lethal currents aren't allowed at these events.

I bet you weren't allowed to generate dangerous amounts of hydrogen gas.

If wasn't a Brown's gas improve the efficiency of your car project was it? ::)

Anyway, back to your original question: can I get 250VDC from a variac?

Yes, it's possible and is pretty easy, providing it doesn't need to be regulated.

Are you sure the output from the variac is 0 to 300V? I'm only asking because it seems an odd voltage for a variac., normally you get the input voltage plus 10% to 20%, there again with no load connected, it'll probably be a bit higher.

Do you measure the output from the variac on or off load?

Does the DC voltage need to be regulated?

How important is ripple?

You need an isolation transformer, to isolate the output from earth ground, for safety reasons.

Here's the simplest solution:

Add a transformer to convert the voltage from the variac to 0 to 180VAC with a current capacity of >2A. Connect a bridge rectifier and a filter capacitor to the secondary, to convert the AC voltage to DC. The output won't be regulated and will have some ripple.

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Making a simple and inefficient HHO bubble generator and a 250V @ 1.5A are completely different things.

We were told by Radio Shack to just build a simple circuit with a Diode Bridge and Capacitor but they don't have a clue what actual parts we need and we are not electronics-smart either.

1. Getting advice about electronics from Radio Shack is like trying to learn French Cooking from McDonald's.

2. Not electronics smart & lethal voltages are a bad combination.

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