i wanted a way to capture lightning photos without keeping the shutter open for lengths of time and i came across a project that seems to fit what i was looking for which works on nikon and with one small change will work on canon too but there was no case for it that i could print so i ended up designing my own, it uses a 9v battery and arduino nano, the 9v must be connected to pin 30 which is marked on the board as vin, if connected to any other pin then wave bye bye to your board. if this will be used on canon cameras then the octocoupler needs to be changed to pc817 as lower resistance is needed.
to my own design i added 2 x 3mm leds, 1 as a power indicator and a second which lights up when the trigger detects lightning, these use 330ohm resistors
the power switch is a simple rocker switch, 18mm x 11mm give or take 1mm.
the lid slides on and off and on the base is a hole which is optional for a helicoil to be inserted incase this is used on a seperate tripod although attaching a shoe mount would probably be better (there are several on thingiverse)
on the link there are 3 circuits, i used the last one as it uses a 10k pot which can be used to adjust sensitivity
the link to the project this relates to is here...