Did you not notice that I labeled R1 and R4 as 1W resistors? If the the opto has the original 5mA flowing through it, then it shouldn't get hot.Hello. There is a problem. The resistors are dissipating a lot of heat when in off mode ( low input). Also optocoupler becomes hot. I am using 817. Is there any way to "shutdown" this circuit in "standby" mode?