Hello, I'm working on a little side project for my home thermostat.
I recently bought a nest smart thermostat to replace my old "dumb" thermostat and ran into an issue with the wires. I don't have enough wires to accommodate all of the thermostat functions. Running new wiring is not an option because that means cutting open a lot of drywall but there is a product called the FAST-STAT wire extender that uses data communication with a transmitter/receiver setup (transmitter wired to thermostat and receiver wired to furnace).
The catch is that this product is very expensive. So I decided it would be interesting to come up with my own version of this with two microcontrollers communicating via serial connection.
The concept is a three wire connection between transmitter and receiver. R-wire is 24vac, C-wire is common, and third wire is data wire. Both transmitter and receiver will be powered by the R and C wires.
The problem I'm stuck on is that the transmitter will receive 24vac inputs from the thermostat that I then need to convert to 5vdc for the microcontroller. There will be a total of 8 inputs coming from the thermostat and more than one can be energized at the same time.
I will already have a rectifier circuit connected to R and C wires to power the board, I just need some way to detect if there is 24vac on any of the inputs then send 5vdc to the inputs on the microcontroller. The simpler the circuit, the better since I would like it to be as compact as I can get it and be somewhat cost effective.
I recently bought a nest smart thermostat to replace my old "dumb" thermostat and ran into an issue with the wires. I don't have enough wires to accommodate all of the thermostat functions. Running new wiring is not an option because that means cutting open a lot of drywall but there is a product called the FAST-STAT wire extender that uses data communication with a transmitter/receiver setup (transmitter wired to thermostat and receiver wired to furnace).
The catch is that this product is very expensive. So I decided it would be interesting to come up with my own version of this with two microcontrollers communicating via serial connection.
The concept is a three wire connection between transmitter and receiver. R-wire is 24vac, C-wire is common, and third wire is data wire. Both transmitter and receiver will be powered by the R and C wires.
The problem I'm stuck on is that the transmitter will receive 24vac inputs from the thermostat that I then need to convert to 5vdc for the microcontroller. There will be a total of 8 inputs coming from the thermostat and more than one can be energized at the same time.
I will already have a rectifier circuit connected to R and C wires to power the board, I just need some way to detect if there is 24vac on any of the inputs then send 5vdc to the inputs on the microcontroller. The simpler the circuit, the better since I would like it to be as compact as I can get it and be somewhat cost effective.