Im trying to find an inexpensive way to take 8-24vac control signals (either on or off) and multiplex them digitally to be transmitted over a 100 foot 24vac power line and then de-multiplex on the other end back to 8 24vac lines to run relays. I was thinking of using res/caps on each line to give a noisy DC level to input into MID400 optoisolators where it would mutiplex into some sort of encoder/transmitter and then receiver/decoder at the other end into optoisolator Triacs. I am not sure what to use as the encoder or how to couple to the 24vac line. Anyone have any ideas?
Im looking for a way to expand HVAC thermostat controls to use existing wiring. The 24Vac transformer on the heating unit supplies the power to the termostat so I dont think I can get around the 24 vac thing since everything in the industry uses it. I would like to be able to put in any new thermostat with more accessories with a simple TX/RX system and be able to control up to eight items just over the oringal 2 or 4 conductor cable.
If the cable is 4 conductor, could you use 2 conductors as your 24vac power supply that is existing and then the other 2 conductors as communications wires? but then there might be an issue with interference. Just a thought.