Thier are also these ways.
"Tube Switched Coil
The ignition that requires the least modification of the camera consists of cutting one of the main leads to the flash tube, and connecting the ignition coil in between. Triggering the flash will produce a spark from the output of the transformer. The advantage to using the flash tube itself to switch the main discharge, is that almost any small switch can be used to trigger the circuit. If the trigger switch is replaced by a thyristor (SCR), the ignition can be triggered by an electronic circuit. The flash circuit itself is mostly intact and not driven out of spec, which means this circuit is quite reliable.
 Manually Switched Coil
The flash tube can also be replaced by a heavy duty switch for triggering, though if the switch is too weak it may become welded shut. This switch will also be carrying the full voltage of the capacitor, and must be properly insulated to prevent electric shock. If the trigger switch is held down for a long time the charging circuit in the flash may break since its output is shorted for the duration.
 Triggered spark gap
Another ignition method that does not require an external step-up transformer, consists of removing the flash tube, and taking out the trigger lead as well as the two main leads. These are then connected to three electrodes, which are placed together to form a spark gap of a millimeter or less. Triggering the flash will ionize the air in the gap and discharge the main capacitor. This produces a more intense spark than the first method, but it requires a more complex park gap. The electrodes can also erode over time, requiring readjustment.
 Trigger transformer spark
The trigger transformer for the flash tube produces a few kV on its own, and can be connected to a spark gap. The advantage to this method is that the main capacitor is not dumped, so recharge time is eliminated and it uses less battery power. The spark is very weak however, and this method is generally not recommended.
 Short circuit gap
A camera flash can be used with a short circuit gap, which has movable points that can be brought in contact from outside the chamber. The flash capacitor is connected directly to the gap and creates a spark when it's shorted. This spark gap is more difficult to make, and may have isues with weldong and erosion, but is easy to hook up and requires little electronics knowledge.
A camera flash can also be used to trigger sprinkler valve solenoids built for mains voltage, however the opening time will be brief since the flash capacitor is drained quickly. "
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