Variable Voltage Ignition Coil Power Supply

This instructable deals with the creation of a very simple high voltage power supply using a car ignition coil. Please take care if you are going to build this as the voltages exceed 30,000. Also do not attempt this project unless you know the dangers of high voltage. This supply can be used for tesla coils and with the right component values produce an arc like a neon sign transformer.

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Step 1: Parts

First of all your going to need:
- A gluegun
- A car ignition coil
- A light dimmer (400w+)
- A capacitor with a voltage rating of around 600v and a capitance between 0.1 and 30 microfarads
- some 2 core mains cable with a flug
- Sunflower oil
- Some bolts
- Some insulated wire (stripped mains cable will do)
- A drill
- Zipties
- A plastic box ( I used a 3Litre box from maplins)

Step 2: Putting It Together

This step is fairly simple.

Live wire:
You will need to wire the live input from the mains to the dimmer and out again.
Then from the dimmer the live wire goes to the capacitor ( make sure its the + terminal if it is a polarised capacitor)
After the capacitor the live goes to the + terminal on the ignition coil

Neutral wire:
This wire goes straignt from the mains to the - terminal on the ignition coil
Also this wire will have to be extended past the ignition coil so it is attached to a bolt through your case. Basically this serves as the high voltage return for the high voltage secondary output.

Middle terminal on ignition coil:
This terminal is high voltage positive and will be arcing to the - of the primary. Run  a wire from the middle of this terminal to a bolt in the case.

This whole setup will need to be submerged in oil to prevent arc overs. Transformer oil is expensive so I used sunflower oil ( £3 for 3litres in Tescos) and it works just as well. Do NOT use motor oil as this is volatile and might explode.

Use zipties to secure your apparatus and cover the drill holes with hot glue to prevent the oil leaking out.

For my power supplyI used a 400w dimmer switch, a 0.1microfarad MOT capacitor.

Step 3: Results

Here are some pics of the output. My camera is crap but this at max ( dimmer turned all the way up) produces around 40KV.


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    33 Discussions


    1 year ago

    Is it possible to build a welding using a car coil run by accu 12 v?

    Is there any DC voltage variable regulator?

    How long it's can run?



    2 years ago

    Can i use a flyback transformer instead of an ignition coil?


    6 years ago

    I have a motor run cap with a voltage rating of 370v
    and a capacitance of 6microfareds.
    Would this work in place of your micowave cap

    1 reply

    Reply 4 years ago

    Yep, your capacitor will work fine. It's close to what I use.


    Reply 4 years ago

    They aren't. I don't expect my coil to live forever, which is why I only run it in short bursts long enough only to light the flammable mixture I need. Eventually it will carbon bridge internally and not work any more. When that happens years from now I can get another coil for next to nothing.


    Reply 9 years ago on Introduction

    true.however this is an inductive kick transformer. What matters is the rate of change in the input voltage. Despite being designed for 12v input, these transformers are very robust arnd can handle 230v no problem.


    8 years ago on Step 2

    pyromadness: Are you crazy or suicide??

    This circuit is very-very dangerous and strictly speaking, lethal!!!

    It uses live mains connectings and the high voltage pole of the ignition coil is directly connected to the mains (because the ignition coil is an autotransformer - do you know what this means?)! You can get lethal shock through that point!
    Nobody use this device!
    (A good question: have any professional ever checked these circuits up??)

    You may avoid the graveyard using a good safety transformer between the circuit and the mains. Nobody use the mains directly when playing with high voltage! Protect your life - or you may get a Darwin awards...

    2 replies

    Reply 4 years ago

    Most fun or useful things can hurt you if you go about it in a stupid way. I am burning hydrocarbons to reach temperatures in a furnace that reaches 3000F and pouring molten metal within feet of my body. The electricity used to start it all in motion is only one small part of the dangerous equation. Use common sense and this is a workable project.


    Reply 7 years ago on Step 2

    the transformer is not connected directly to mains, the capacitor and ballast linit the current significantly, and its boxed up.

    I do agree it is still very dangerous, but so is everyday risks, like walking down stairs, i can always trip fall, and break my neck... and if one take extreme caution with the circuit it is fine.


    4 years ago

    Thanks for the write up. This circuit works great, I have made two of them, one to light my waste oil fired foundry, the other lights the waste oil heater for my garage. I used an el-cheapo dimmer and a 370/480v 10uF motor start capacitor and it lights oil vapor every time.


    5 years ago on Introduction

    I had something like this that was professionally made, and I believe that it had about 50,000 volts (1955?) when I was about 10 (we used to trade toys like this, bb guns, sling shots and fireworks). It was a plug in device, and it had two curved rods that were very thin where the lightning bolt would jump from one side to the other. Each rod had a wood extension so that you could adjust the distance. The box was about 12" x 12" and the spark would jump as much as 8 inches or so. It did not feel particularly good when you put your hand in the way. Don't ask how I am still here, today.

    There is a great use for these things. I grew up in the age where all the adults smoked their filterless Camels and Pall Malls. If you know someone who smokes sneak out a couple of their weeds and put them in the path of the sparks being sure to do as much of the cigarette as you can in a bunch of directions. Then sneak them back into the pack.

    You won't see any difference in the cigarette (at least with the machine I had), but watch as your friend starts to take a drag. It is like sucking on a 4 inch drain pipe filled with one inch holes. Your friend will start sucking so hard that you would think he was deflating a basket ball in two seconds. You won't see the smoke drawn into the weed.

    to an extent, yes. When the dimmer is fully turned up, rate of change in the input voltag is highest so the output voltage its at its maximum.