Hello guys,
I am not sure if this is the correct thread to post this topic on, but it is related to microcontroller, so here is goes.
I have a 120vac input signal coming from an existing sensor that i need to sense to my controller and then act accordingly. I have tried 2 circuitries and have success with both but there is a trust factor missing. I want it NOT to fail down the road because of heat issues etc.
1. Is using a bridge rectifier with a 20k 2 watt resistor, 0.5uF 200 V cap going to an opto coupler and from there to my controller. Works perfect but the resistor is starting to heat up. The location of installation wont have much ventilation so i am worried it will burn out. The math shows 2watt should be enough but apparently it aint. I can go higher, maybe lets say 3-5watt, but still with no ventilation, it has chances of failure.
2. Option 2, and everyone is going to hate this, including myself is using a capacitor on the AC side, 0.33uF to limit current with a 10ohm resistor, 470k ohm on secondard side of the bridge with 1000uF cap for smoothing, goes into the opto, also works perfectly. But safety is the concern.
i cannot make up my mind on what else i can do here or somehow perfect what i have with either option 1 or 2.
looking forward for some feedback.
thank you.
I am not sure if this is the correct thread to post this topic on, but it is related to microcontroller, so here is goes.
I have a 120vac input signal coming from an existing sensor that i need to sense to my controller and then act accordingly. I have tried 2 circuitries and have success with both but there is a trust factor missing. I want it NOT to fail down the road because of heat issues etc.
1. Is using a bridge rectifier with a 20k 2 watt resistor, 0.5uF 200 V cap going to an opto coupler and from there to my controller. Works perfect but the resistor is starting to heat up. The location of installation wont have much ventilation so i am worried it will burn out. The math shows 2watt should be enough but apparently it aint. I can go higher, maybe lets say 3-5watt, but still with no ventilation, it has chances of failure.
2. Option 2, and everyone is going to hate this, including myself is using a capacitor on the AC side, 0.33uF to limit current with a 10ohm resistor, 470k ohm on secondard side of the bridge with 1000uF cap for smoothing, goes into the opto, also works perfectly. But safety is the concern.
i cannot make up my mind on what else i can do here or somehow perfect what i have with either option 1 or 2.
looking forward for some feedback.
thank you.