Can you use a full bridge rectifier off of 1 AC line?

Other Hardware General Electronics
41

If I were to want to take intercept / control of what the thermostat was currently doing I wouldn't touch the thermostat wiring at the thermostat.

I would use an AC input optocoupler back at the HVAC unit for each of the controls Fan, Heat & Compressor. Disconnecting them from the HVAC unit.

GPIO input the output of the opto's, perform what ever calculations needed using the Arduino and control the Fan, Heat & Compressor using relays. I would not use the cheap "for Arduino" relay boards on my HVAC system, I'd use something more reliable. But that is just me.
Note: There will be no need for the "C" terminal at the Thermostat.

42

#14 is where the wires attach, #34 is the back of the thermostat.

43

Is this product?

https://www.enviro-tec.com/pdf/iom/honeywell-69-1714.pdf

44

Right where I asked him for it, thanks.

45

Wrong, put a new battery (duracell battery )

It doesnt, it is a battery operated.

47

Hi, @klzsh
This appears to be your system.

hvac1
hvac1511×617 40.2 KB

With G , W, Y being switched to 24Vac (R and Rc) to energize the appropriate relay.

Tom.... :smiley: :+1: :coffee: :australia:

48

yes, I already looked at the pdf

49

seems correct

50

the thermostat works, but we haven't replaced the battery ever. it runs in 2 aa batteries.

51

That's my point. If you select a low current relay or P-MOS option, a screen with a low-power mode and a switch(or gesture sensor) on the backlight, and an Arduino on low power mode then there's no reason you can't stick a couple 18650s in there and call it a decade.
Or follow what @johnwasser suggested and use 2 Arduinos and repurpose your wiring; that's a no battery solution.

52

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