Connecting to Mitsubishi Heat Pump CN105

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I got a Mitsubishi Heat Pump, which has pretty limited thermostat options, so I decided to build my own thermostat. There’s some basic connectivity info as well as a library that talks the protocol but I couldn’t find a ton of specific information on how to make the physical connection.

I used the following parts:

  1. JST PAP-05V-S housing
  2. JST SPHD-002T-P0.5 contacts
  3. Tensility 30-00394 4 stranded conductor 26AWG wire
  4. IWISS Crimping Tool

This crimp tool is definitely not the correct one for these contacts, but I managed to make it work. You should order at least twice as many contacts as you’re going to need because crimping is such a pain. (I started with 0 crimping skills. If you know what you’re doing then maybe it’ll all be easy.)

(Chris M reports success using simple crimp wires and soldering them instead of trying to crimp. He covered up the solder joints with heat shrink tubing. That’s probably a better method.)

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Once you have the parts, they go together how you would expect. Crimp the contacts onto wires in the cable, then insert the crimped contacts into the housing. Because I did not want the 12V signal I just used a cable with 4 conductors. These conductors have to be stranded, otherwise crimping won’t work.

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The picture above shows where to plug in the cable. It’s the red receptacle labeled CN105. My board nicely labels pins 1 and 5. (The marking for pin 1 is hidden in the picture, but you can clearly see the number 5.) The pin mapping is:

4TX, data from heat pump
5RX, data from thermostat

Once it’s all done, the cable should snap cleanly into the receptacle, and come out when you press the tab.

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Living the good life in Seattle, occasionally sharing something interesting with the Internet.