I must admit I was lazy enough to use this calculator, but in fairness it does provide you with the closest resistor to the value you can actually buy, which is pretty handy. If you weren’t satisfied with my explanation, maybe can help, but I wouldn’t know as I haven’t even ...
Initially I had thoughts of a two unit system. One sender unit mounted on the garage door and a receiver unit that sat inside with an indicator light with RF comms using one of the many different types of Arduino RF shields. But this was complete overkil so in the end I settled on 2...