I'm designing an ATmega328 PCB with an optoisolated TRIAC controlling a 100W (~ 0.5A, 230V, PF = 0.98) load. I'd like to monitor the current with the processor and report an error if the current drops. The load is an electronic ballast driving 3 fluorescent lights and they are wired so that if one goes out, all of them go out. Therefore I only need to know if there is current present and not really measure it.
So far I've encountered 3 different solutions:
- A current sensor IC like ACS712 that uses the Hall effect (I later found out that ACS712 is not suitable for mains voltage)
- A shunt resistor with an opamp (galvanic contact problem due to Vcc on opamp)
- A current transformer for galvanic isolation and shunt resistor like in the previous point
I have no idea which one is the easiest to implement (and cheapest) and which one is the safest. I'm not really sure about the exact circuits I should use for either of the solutions.
I'd really appreciate some help on this matter as well as an appropriate circuit. If there is more information needed let me know.