I would like to replace a piezo igniter in a small project with something that can be electronically controlled (I have created some simple hairspray-powered foam rockets, and I would like to be able to sequence several of them from a computer).

It looks like pulse igniters, [like this](http://amzn.com/B00NM8VIE4), are relatively inexpensive, but it's been hard to find any documentation or wiring diagrams for them and I'm unsure if I understand all the connections.

There are obvious inputs for power and for a switch, but on the high voltage side there are three wires, labelled `HV1`, `HV2`, and `S`. `HV1` and `HV2` appear to come off either end of a coil, and `S` is a mystery.

The igniter looks something like this:

[![Diagram of the igniter](https://i.stack.imgur.com/l9KB6.png)](https://i.stack.imgur.com/l9KB6.png)

And the innards look actually like this:

[![Inside of igniter](https://i.stack.imgur.com/BGrf3.jpg)](https://i.stack.imgur.com/BGrf3.jpg)

`HV1` to `HV2` seems to generate the most effective spark, but I don't know if that's using the igniter correctly or slowly frying its innards. Can someone help explain these labels?