The next stage in this project is to start experimenting with hardware. Here you can see the (almost) complete setup. The yellow switch is the safety interlock, the orange push-switch simulates the igniter. The only components not present yet are the audio alarms for the various state indications.
After some rudimentary testing of the Wemos D1 Mini Pro, it seemed like a viable platform on which to build the system. It has enough GPIO pins, has a nice form factor, uses only about 80mA when running (not just idle) and seems stable.
What would be critical to the projects success however, would be the range both it and my mobile phone WiFi hotspot could achieve.
I knocked up a quick mobile version of the hardware, utilising the onboard LED to indicate the state of the WiFi connection.
With the external antenna connected, I managed to achieve a comfortable 100m range between the Wemos and my beat up, old Samsung Galaxy S7 as the hotspot/AP. Realistically the connection was dropping at around 120m, but I didn’t have the means to accurately measure the distance so I’ll stick with the 100m claim – still perfectly good enough for my needs.