OneWire circuit

So I’m having thoughts of wiring my house with a bunch of sensors but would like to limit the amount of wires as much as possible. Ofcourse that would best be done with some kind of OneWire circuit. One wire for ground and one wire for data and power.

I’ve experimented in Falstad’s circuit emulator and so far this is what I’ve come up with.

fiacrop1

The 470uF capacitor keeps the remote circuit (here its just a 1k resistor) powered while the data line (A) is pulled to ground to send signals. The resistor-transistor at the power source limits the current so it won’t short-circuit. The switch will be replaced with a MCU of some sort to control the sending of data.

I’m thinking of CLR, DATA and CLK going into a 74HC164 serial-to-parallel chip. Pulling the data wire (A) to ground very briefly would latch a 1 (one) as CLK goes back high, pulling it to ground a little bit longer would drain the 4.7uF capacitor enough to register a 0 (zero) when CLK goes high and finally pulling the wire to ground long enough to drain the 10uF capacitor would make CLR go low and reset the HC164 (asynchronous active low).

Timing depends on the values of the capacitors. Ofcourse at point (B) the voltage to power the MCU would be only 3V, but an atmega or attiny will run on that. It’s even possible to have several sensor circuits on the same two wires.

Now I just have to go from drawingboard to physical circuit and make it work…

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