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  #1  
Old 06-07-2012, 07:00 PM
rudyauction8 rudyauction8 is offline
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Question building step up circuit 12,000 volts - help!!!

I was wondering... I saw some 120-12.6 volt transformers at radiosnack, if I used 3 reversed in series, and used 12 volts AC to power them, would they give me ~12,000 volts or short out somewhere along the way. I am trying to make a circuit that generates small sparks. I was thinking a large one (~3 amps) first, then small ones (~1 amp) for the higher voltages. I know they aren't designed for high voltages, but would they work? They only need to last for a week or 2.
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Old 06-07-2012, 07:14 PM
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Not work. The second transformer would be fed with 120 volts on its 12V winding. Fast smoke. Better to try the transformer out of an oil furnace ignitor.
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Old 06-07-2012, 07:23 PM
rudyauction8 rudyauction8 is offline
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Even though the 120 volts will only have a current of about 50ma? I was going to use a 500ma 12v AC power supply for this. If it will smoke out, then I may be out of options. I could also use single pulses of 12volt dc to reduce load. Or does it short out because the 120 volts goes through the insulation? I'm honestly more worried about the third, when 1,200 volts is fed into the 12 volt coil at something like 1-5ma.

Is it possible for me to make my own transformer(s)?
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Old 06-07-2012, 07:27 PM
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Hallo,

There probably will also be problems with the isolation of the transformers.
It can be that there are sparks made INSIDE the transformers that may burn the transformers.

Bertus
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Old 06-07-2012, 07:27 PM
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You are correct to be more worried about the third stage. Whatever might go wrong with the second stage will surely go wrong with the third stage.

There are many ways to make a spark. Car ignition coil is one way.
It is possible to make a transformer, just much easier to find one that is already good enough.

Please describe your goal more fully.
Other helpers, please contribute ideas.
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Old 06-07-2012, 07:41 PM
rudyauction8 rudyauction8 is offline
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my goal is a simple to build circuit that can generate sparks at least once per second that are about 1cm long, give or take. A car coil would work, but how does the circuit around it work, and how high of a voltage can I get from it? I would like to push what ever I use to the limit, if a car coil can give me 1 inch long sparks, that's what I will do. This circuit is just for fun, so the only restriction is the price. I can pick up a car coil at a junkyard today or tomorrow, but first, I need to know the details of how it works.
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Old 06-07-2012, 07:54 PM
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I'd say a 555 timer oscillating at 1Hz with a low duty cycle, to a MOSFET that allows current through the low voltage side of the coil. When the MOSFET shuts off, a frewheeling diode allows the primary coil to collapse and the secondary coil kicks out a spark.

is that enough?
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Old 06-07-2012, 08:03 PM
rudyauction8 rudyauction8 is offline
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I understand up to the diode. How and where does it go? I'm new with transformers. And how much voltage can I use? Could I use ~24 volts for a bigger spark? I have a few 18-30 volt power supplies from laptops to work with. Again, it only has to last a few weeks of 2-3 minute uses.
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Old 06-07-2012, 08:08 PM
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AAC user DEBE has already done all the work for you here:

http://forum.allaboutcircuits.com/sh...ad.php?t=50728

You may need to vary the 555 timing to suit your needs
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Old 06-07-2012, 08:19 PM
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I can't top that!
However, I can give you a dirty look for trying to up the voltage until you finally get it to fail.
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