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Help with transformer spark (probably simple if you are knowledgeable on the subject)? Answered

I am building this poster that is for a school project that is supposed to be about me so I decided to do it on electronics. One of the parts is a small spark that I am trying to make.

The difficult thing is that I am trying to make it from a battery supply (whilst using a transformer) and that I am presenting it so the spark needs to be pretty visible and noisy.

I had a wall power supply that took 120VAC and output 4VDC. I removed the output smoothing and rectifying circuitry so all I was left with was a transformer.

I connected a 9v battery to what used to be the output through a pushbutton switch. Then I placed what used to be the 2 input wires (there is a center tap as well I think) close together. Upon clicking the pushbutton switch I get a spark of maybe 1mm. (the spark seems to jump when I open a previously closed switch rather than when I close it.

Is there a way I can use a capacitor to get a more sustained charge? My results were faint in sound and visually. I need to present this to a room.

Is there a way I can automate the switching process? I tried to use a ceramic resonator but I have little understanding of how those work since I have only used them in embedded electronics and would just align the proper pins. I am thinking about sing a 555 timer and tying the output to a transistor which would supply the transformer with 9VDC.

Is there a way to get a spark from DC battery supply without a transformer? It seems like the transformer adds complication since it is made for AC.

I am thinking about tying the output of my current setup (which produces a small spark) to the input of another transformer. Will this work? Will the spark become even more faint if I do this?

Thanks, and I understand that I am working with HV at my own risk.


If you want some more drama, adding a fluorescent tube light might help. I mean: you put it series with the output of your transformer, and it will flash briefly with each high voltage pulse. This simple trick may be all you need. Also you could dim, or switch off the lights. That way, even the people sitting in the cheap seats can see something happening.

How about a fake-spark?
Use a camera-flash unit to produce a flash, but build it into the board so it looks like a big arc. Maybe fit a stencil over it



Thanks for this post, I think I will use it. I was looking to make a real spark but for it to be visible it has to be dangerous and not made with what I have on hand.

You're right there. A bright flash should get noticed enough though, and in real terms it would still be a high-voltage plasma, just contained in a glass tube.


It would be difficult to make a stage-effect spark that would be AUTHENTIC and LOUD and VISUALLY bright.... and cheap/safe to make. For this reason, a FAKE spark is the way to go. I agree with LEMONIE.

Is there a way I can charge a row of capacitors in parallel (say 10) and then Switch them to series so that there voltages are added when they discharge?

Yes, its called a Marx generator, and it can be lethal.
L. has a great suggestion, easy to make, safe and spectacular.
I'd add that you can buy ultrabright LEDs and get a similar effect.


How big a spark are you after ? You need more volts to get more spark, a rule of thumb is about 1000V /mm.

A Tesla coil is the simplest way to get big, relatively safe sparks.


It is supposed to be on a poster board (although I will probably use a square piece of wood or cardboard). I do not plan on making a complex or complete system like a tesla coil, just something quick and dirty.

Also, you say more volts for a bigger spark. I understand this in terms of spark length, but what about visibility and audibility? It seems like that is associated with the current. So, if I were to go for another transformer, I am guessing that my spark would be longer but wisp-like. That was why I thought of incorporating a capacitor but I can't figure out how to do so.

More current will help, but high voltages, high currents, open arcs and school don't go together.