QUESTION: operational lifetime circuit/system

Brevor said:

Hello Ozgur84,
Not really much to explain, Where I work we have several "air handlers" large blowers that circulate the air.
The devices I made simply connect to the blower motor power source (120 V 60Hz) and counts how many hours the blower motor runs. At 500 hours it lights an led to alert a maintenance worker to replace the air filters.
When the filters are replaced the maintenance worker pushes a reset button that turns off the led and resets the hour counter to zero. It uses a Microchip PIC 12F629 to count the runtime. It saves the registers to EEPROM in the event of a power failure and then restores them when power returns.

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Thanks Brevor, I think I will also follow the same solution because it seems most cost effective solution probably with a coil meter as dr pepper's suggestion. One question, does your system write the data to eeprom after each completed hour or does it make a calculation between the switch on and off time and write the final value at the end?

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