what im trying to do is lets say a house has a upstairs and a down stairs, with one air conditioner, a thermostat for up stairs and downstairs, think of the thermostat you have in your house on the wall
each t stat has 3 wires i need to choose between ( heating, cooling and a fan ) i cant have both thermostats sending information at once so i have 3 relays to switch them, depending on if the relays coils are enegized, now i need a timer circuit that alternates them every 15 min if both are calling at once, so basically if normally closed thermostat calls first, then normally open thermostat calls second and starts a basic astable timing circuit the first cycle will be on therefore giving the normally open thermostat priority because the coils will be energize, its supposed to work by giving what ever thermostat called first 15 minutes then cycle,
here is a diagram of how the relays are set up and the coils are gonna be controlled by the timing circuit and the timing circuit is gonna be turned on when any 1 wire on each thermostat has power at the same time
basically the relays switch complete controll of the a/c unit depending on if the coils are energized or not