I need to detect by if one o more pumps are really connected to the 230 Volt main supply. Each pumps is activated by means of a triac isolated by a MOC3021. Arduino commands the optoisolators and I need to detect if really the triac has switched on (e.g. the triac didn't switched due to a fault).
The solution has to be possibly cheap and reliable. I found this simply circuit from a site, and I would like to know your opinion. The optocoupler is a 4n35 or pc817 or similar. What also I need to know is if the 390K resistor should be dimensioned more than 1/4 W and if has to be a special resistor for high voltage. Thanks a lot.