A 5v humidifier is now providing the "smoke" while the toggle switch activates the warning LED, buzzer and push button. Pushing the button activates the 12v solenoid, which automatically resets to avoid overheating. The mode selection from the potentiometer bounces around a bit, so I'll have to work on that, but now I'm looking at a test housing to work out how to lay everything out so the steam is kept away from the electronics.

Hi Jonathan, great to hear from you. I'm in Northern Ireland. My nephew Dave (also in the group) formed a local rocketry club. I'm working on a miniature rocket model for use at indoor displays. It will let kids play and donate to raise money for rocketry clubs. I'll be uploading the schematics and STL files for 3D printing when it's done. What size of rockets do you launch?

@Jonathan Greig crikey, they left look amazing 😀