Mitsubishi AC hacking

I am trying to get an Arduino hook up with a Mitsubishi AC system but it seems tricky.
I have few Mitsubishi Fden140: http://www.orionairsales.co.uk/mitsubishi-heavy-industries-air-conditioning-fden140v-ceiling-145kw--48000btu-heat-pump-inverter-70-p.asp
There is the main thermostat which is connected with 3 Wires ( picture attached ) but I have no idea where I can find some information about what these cables do.
Probably 2 of them carry power ( V+, GND ) and the 3° is like signal.

Can someone help me out to find out some more information about this system? Or How to try to hack it’

max246: I am trying to get an Arduino hook up with a Mitsubishi AC system but it seems tricky. I have few Mitsubishi Fden140: http://www.orionairsales.co.uk/mitsubishi-heavy-industries-air-conditioning-fden140v-ceiling-145kw--48000btu-heat-pump-inverter-70-p.asp There is the main thermostat which is connected with 3 Wires ( picture attached ) but I have no idea where I can find some information about what these cables do. Probably 2 of them carry power ( V+, GND ) and the 3° is like signal.

Looks to me that the module is mains powered. DR1 and DR2 look like they form a bridge rectifier and IC1 looks like a voltage regulator. The colours of the attached leads tend to confirm this. I can't see any output on it, but this (these) maybe on the underside and make contact with a fitment on the case.

Or whoever has wired it up has used a piece of "twin and earth" and is using the earth wire to carry a signal (5VDC or 230VAC? !!!) :fearful: :fearful:

If that's a thermostat it's a mighty complicated one incorporating a fully pblown processor

The picture has a partnumber that can be Googled: pja505a124. First result will be a service manual, and on page 36 of that you will see the front of this unit, called a wired remote controller. If you have a look at the picture here and compare it to the one in that manual, you can see the tabs coming through the pcb, holding the LCD on its place. You can also see that it has the same outline, and it is very well possible that the other side of that pcb has buttons on it. This service manual tell you about how to program the unit (i did see some remark about entering some test run), but it doesn't tell anything about how to connect it, or how it communicates.

In an other part of that manual, red is supposed to be 240 V live wire, white neutral and yellow/green is earth. This is different from the colors visible on the photograph above, that has texts red, white and black printed next to the terminals.

How to find out what each connection does involves a multimeter at least, and perhaps an oscilloscope.

MAS3: In an other part of that manual, red is supposed to be 240 V live wire, white neutral and yellow/green is earth. This is different from the colors visible on the photograph above, that has texts red, white and black printed next to the terminals.

The colours of the wiring in the phote correspond to that scheme. The standard UK (EU?) colours are: Brown = Live, Blue = Neutral and Green & Yellow = Earth. The colours printed on the unit may be the standard wiring colours for elsewhere in the world.

jackrae: If that's a thermostat it's a mighty complicated one incorporating a fully pblown processor

As far as I can tell, it isn't a thermostat! It's some sort of controller.

I know I am a few months late to the party, but I am also interested in hacking it :)

I have come as far as finding the manual, and sniffing the signal pin. I have decoded a few of the bytes, but am still searching. If anyone is interested we can work together :)