What Battery and Capacitor Are Best for a DIY Spark Plug Ignition Circuit?

[nukengr10]

My friend and I are trying to build a very basic to get a spark plug to fire. Right now we have a plug, and Ignition coil that outputs 20 kV. The Ignition coil says on it 12 V and was bought at an auto parts store so I am assuming its an ignition coil for a car. What kind of battery should we test it with? Do we need as much power as a car battery or can we live with a much smaller size? Also i heard about using a capacitor to absorb the back emf in the primary coil that will run across the switch normally. i was thinking maybe a high voltage capacitor of like 10-100 microfarads?

 

[Marty]

I've done this circuit a couple of times. The first time I did it I tried to theoretically calculate the value of the capacitor. It was a pretty interesting problem in a lot of ways. I can tell you my calculated answer was around 0.010 microfarads, but I won't bore you with the details. The voltage won't be more than about 400V because the ignition coil has a turns ration of around 100:1.

There's a lot of physics in the circuit, but the most fun is making sparks. I got the best fireworks by dragging a screwdriver across a long piece of threaded rod.

Marty

 

[piercas]

Hello! It sounds like you and your friend are working on an interesting project. The spark plug ignition circuit is an important component in the functioning of a car engine, and it's great that you are trying to understand and build a basic version of it.

Firstly, it's important to note that the 12 V on the ignition coil indicates the input voltage required for it to function properly. This means that you will need a 12 V battery to power the ignition coil. While a car battery may work, it is not necessary to use one. You can use a smaller 12 V battery, such as a motorcycle battery, as long as it can provide enough current to power the ignition coil.

As for using a capacitor to absorb the back emf in the primary coil, this can help protect the switch and other components from damage. A high voltage capacitor of 10-100 microfarads should be sufficient for this purpose. However, it's important to note that the exact size and type of capacitor needed may vary depending on the specific design and components of your circuit.

Overall, it's important to carefully consider the components and their specifications when building a spark plug ignition circuit. It's also a good idea to consult with a knowledgeable person or reference materials to ensure proper functioning and safety. Good luck with your project!