Context: I'm trying to design a little monitoring circuit that will tell me when my air conditioning is interrupted by my utility's "Saver Switch" which reduces load during peak times.
Specifics: Central air conditioners normally receive a signal to turn on their compressor by having 24 VAC applied to two terminals on their control board by the thermostat (a switch). In my case my utility has wired another (remote controllable) switch in series with the thermostat which can be turned off during periods of high demand preventing the compressor from being run. I would like to monitor the state of both the thermostat switch and the utility saver switch independently. I would also like to monitor whether 24 VAC is being applied to the compressor control board.
Goal: A circuit which will provide three 5vdc logic outputs one which shows whether the thermostat switch is open or closed, one which shows whether the utility saver switch is open or closed and one which shows whether 24 VAC is being applied to the compressor terminals. If any one of the three logic points is low the compressor would not be running, if all three are high the compressor should be running.
Does anyone have some suggestions about how to do this? It seems to me the tricky part is measuring whether the switches are open or closed as they may or may not have 24 VAC flowing through them.
Thanks!