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Schematic - Push Button Fire
The Build
I ended up using a Sonoff SV since it had everything I needed. The Sonoff SV also has 3 GPIOs available which I used for a RGB LED. It also exposes the GPIO-0 (button) which I used for the foot pedal. The foot pedal made things so much easier.
I originally powered the SONOFF SV off of the battery but found that it would cause the SONOFF to reboot sometimes. So, I ended up powered it with a dedicated 12V 2A power supply.
I programmed the SONOFF micro-controller (ESP8266) to open the relay for a number of microseconds in order to perform the weld.
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