A finished view of the “Auto-Fire” controller box. The 10-turn pot allows fine control of the firing rate. It ranges from around 1 shot per second to 17 per second. On and off periods are identical, i.e. 1 second open, one second closed. Future iterations will allow adjustable periods independent of each other.
The timer circuit is based on a 555 timer IC and a solid state relay. It’s a 4 channel relay so it has expansion possibilities.