Capacitor discharge ignition system ( PIC 16F615 )

Posted on Aug 29, 2012

This device uses a PIC12F615 to implement a capacitor discharge ignition system. When the switch (button) is closed, the PIC sends pulses to the IRF644 MosFet creating high voltage pulses to charge the 1.0 uf/250 volt capacitor. The voltage is read back via a 1M/10k divider until 200 volts is reached. Then the SCR (mislabeled triac above) is fired and 200 volts applied to the primary of the ignition coil. Note, the 12 volt zener is needed to let the capacitor discharge to zero and allow the SCR to reset.

Capacitor discharge ignition system ( PIC 16F615 )
Click here to download the full size of the above Circuit.

The resulting spark is about 1/2 inch to a spark plug with a modified gap. Most of the electronics and momentary switch are located in the handle. Unscrewing the coupling to the barrel allows the (high carbohydrate) projectiles to be breach loaded. Unscrewing the rear fitting access the main chamber to inject the propellant (I've been using lighter fluid in a nasal inhaler bottle - really works great!) - here are some other propellents that we have not tried. Coating the marshmallows with flour keeps them from sticking in the barrel and improves performance. Watch out when they get a bit stale, they really come flying out then and may go several hundred feet. Don't forget to 'air out' the chamber between firings, or you won't get any real action. Here are the Layout SOURCE and Hex files.

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