I'm pretty new in the Arduino game, and also my basic electronic skills are not the best, so please bear with me.
I'm thinking of making an ethernet based AirCondition remote control.
I want to do this by emulating the remotecontroller which is IR based.
But insted of using IR at all, I thought, will it be possible to solder an Arduino pin directly (or thru some electronics) to the IR reciever inside the AC unit. This way I can put the ethernetboard inside the AC unit and be happy?
I have never seen IR used with AC... But I have lived a sheltered life
There are two kinds or IR receivers... Active (3 wire) and passive (2 wires.)
If the receiver unit is a 38KHz standard 3 wire receiver, yes, you can pull off the TTL signal lead. If it is a passive 2 wire sensor, you could introduce noise into the receiver and muck it up.
IR remote controls are common with AC units, and differ from normal TV remotes in that they typically send a very long sequence, of the full configuration every time - so not as simple as TV IR signals. Otherwise the signalling is similar.
As you opened your post saying that you have limited experience, I would tend to suggest that you don't make a direct connection, as there will be AC voltages within the casing & any warranty may be compromised. You may also find that if the unit fails the engineer wont touch it if it has been hacked on the inside.
It sounds as if you would be better starting with sending IR from the Arduino, once you have first captured the AC IR signals. The IR remote library is excellent and there are several examples in the blog of people who have done what you want with IR.