IR emitter inside AC unit

[Sean123]

Last week the remote on my Airwell air conditioning unit stopped working. In a pure Murphy-inspired coincidence it failed on the exact same day when a service man was scheduled to come perform the yearly maintenance. After some embarrassing moments when I couldn't get the thing to start he got it going with manual controls.

I quickly verified with a camera that the remote control is actually transmitting, so the problem was obviously in the unit itself. He didn't have any spare parts with him so I decided to look into the issue myself before calling the service again and he was kind enough to show me how get the cover off. With the cover removed the location of the IR receiver board was immediately obvious. Right next to some shoddy wiring work that made me immediately reach for my soldering iron and shrink-tubing. I know electricians despise using a soldering iron, but you do not connect wires on a kilowatt-range equipment by merely twisting them together.
Any way, this is the so-called receiver board. In fact it holds four visible diagnostic LEDs, one high-intensity IR LED and one integrated optical receiver module, all on independent circuits. The receiver also has a tank capacitor on its supply line and a common-collector amplifier on its output.

Nothing was obviously broken and after connecting the receiver part to 5 V supply it sort of worked. However the output signal wasn't swinging rail-to-rail as it should be and it seemed to be affected by mechanical stress. None of the soldered joints seemed faulty upon visual inspection, but after reflowing them the problem went away.

I wonder what the IR LED is used for? It can't be for two-way communication with the remote control, because the remote control only has two LEDs and no receivers (at least that's on the model I have). When the unit was working again I checked with the camera and the IR LED is indeed active and seems to transmit something whenever the receiver receives a command from the remote control. Perhaps it is for synchronization if multiple units are installed in the same room?
By the way, the remote control emits a burst of data whenever a key is pressed. The packet is quite large, taking more than 200 ms to transmit. This is several times longer than in ordinary, say TV remotes, so it looks like it transmits the entire state, not just individual commands.

[AnalysIR]

Topic moved by ADMIN

[AnalysIR]

Interesting story.

Can't say I am certain, (not a lot of AC units in Ireland) but 4 possibilities spring to mind:

- As you said syncing multiple AC units in the same room/area
- Configuration/maintenance by Technicians.
- Could also be an option with some remotes to ACK the reeived signal??
- Could be a generic board used for multiple purposes

However, given that your signature linked to a commercial AC company, you probably know the answer already!

[ConnieKeefe]

hanks for answer me! right now I am in work, but as soon as I get home I will look at the model number of the remote, the model number of the A/C unit is 38MPQ2405, the receiver`s model number is TK 2236, yesterday I tried to control a GOODWEATHER unit, and something funny happened, the unit only responds if I send the signal in an angle of 90 degrees, unfortunately I do not have the model of that A/C, may that be because of the incorrect type of IR Receiver that I am using?
the thing is, I am running out of time to finish this proyect, it is my final university proyect, the idea is to create a device that control most of air conditioners as posible, using a web interface, the device must be interoperable with a domotic system, but that is an history for another time.

I am really interested in buying the AnalysIR, will you recommend it for people with very limited programming knowledge?, I want to buy some of the kits to, but we do not have paypal system in my country, is there another way to purchase it? another thing, I am from Paraguay, so I wonder how much time it is going to take for the components to arrive. (because of my running out of time issue).


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[AnalysIR]

To use AnalysIR, you should be familiar with Arduino (or equivalent). You should also understand a bit about IR remote control.

I am not sure about the 90 degree issue - it could be that the IR receiver in the AC unit is dislodged or obscured in some way. Direct & reflected sunshine can cause lots of issues.

AnalysIR makes things much easier, but you still need to do some work.

PayPal is the only method available at this time. (It may be possible to use a credit card with PayPal, without an account. (Several users got friends to make the payment on their behalf)
via this page http://www.analysir.com/blog/get-analysir/