Ignition Coils

Okay, so what the FRICK is an ignition coil? Well if you know a little about cars, you'll know that a 4 stroke engine goes SUCK, SQUEEZE, BANG, BLOW. Literally.

The BANG bit utilizes an ignition coil to produce a spark across the spark plug, initiating the power stroke of the engine.

Ignition coils are essentially pulse transformers. Transformers that work using pulses of current, instead of standard alternating current. These pulses that are applied to the primary coil are magnified and the voltage appearing from the secondary coil can be up to about 40kV.

I managed to get the ignition coil in the picture above for $5 from the local car wreckers.

By the way, old cars also have other goodies in them, like bits in the dashboard, or money in the glove box (haven't come across this one yet...).

Here is Aidan scavenging through an old trashed up car in some scrubby location.

To run the ignition coil outside of the car, specialised circuitry is required that produces pulses of voltage to the primary coil. I took a very common design (the 555 timer driving a MOSFET) and built it. Well, more like lashed it up, as seen in photo.

In the photo, it shows the first firing with two ignition coils. The spark pictures below were actually with only one ignition coil, since I blew one of them when it arced over inside.

Here is a poor circuit board being electrified. Notice the corona at the top of the wire. This is due to the roughness of the copper, as very sharp points lead to the build up of charges and hence charges leaking off very fast (corona).

Also notice how the sparks immediately tend to the grounded metal objects (the tops of those capacitors).

Those sparks are about 4cm long, an estimated 44kV (1.1kV/mm).

Exposure is 1 second.

A demonstration of what happens in a lightning cloud. The charges build up on the tip of the wire and discharge onto the circuit board below. It discharges here because the other side of the ignition coil is connected to the circuit board.

Notice how the spark isn't anywhere near straight, it all depends on the temperature/humidity/wind draft of certain spots in the air.

That spark is estimated at around 50,000V.

This is what happens when the wire is brought closer to the board. The sparks are produced much more frequently, as the charges don't have to build up for as long anymore.

So intense that the camera is saturated.

Any guesses what happens when the wire is brought even closer?

When the wire is brought very close (this is about 1.5cm), no sparks occur anymore, just a continuous arc. The charges no longer have to build up very much, and immediately jump onto the circuit board.

The temperature of the arc exceeds 10,000 degrees Celsius.

Notice that stray spark catching the other corner of the metal can. This is probably due to wind drafts.

In this similar photo, you can see that the air around the arc is heated super hot. The metal can is untouchable after a few seconds of arcing.

By the way, this is what happens during arc welding, except the arc is much longer here (though not as bright and fat).

A demonstration of the ineffectiveness of normal plastics as insulation at these very high voltages. The sparks simply track along the insulating plastic until it reaches the grounded terminal at the end.

That's why power companies utilize ceramic disk insulators... ceramics are the best insulators known. Some particularly poor insulators at high voltages include rubber, plastic, paper and wood.