I'm building a web-controlled IR remote control for my air conditioner.
you know how when you press the power button on an AC remote it turns on the unit to the selected settings, but if the unit was on, it turns it off? Well, there's my problem.
I need to come up with a way of determining if the AC is on, so I know what signal to send it. It would be nice to also have the ability to know what setting it's set to, but I could live without that.
I can't hack the AC itself - this is a rented apartment, and I don't want to modify my landlord's AC.
I plan on having the remote I'm building sit across the room from the AC, connected to my home router, and would prefer not having to run wires across the walls.
I used to be the manager of an offshore oil production platform and we would (infrequently) experience the loss of main power generation - with critical systems falling over to UPS power generation.
Our control room team asked for a simple device which would advise them when main power had failed (yes they had bells and whistles capable of doing it but that's control room operators for you)
So one of our bright sparks fitted a lamp to the front of their control panel and plugged it into a power socket. He then stuck a big label onto it reading :-
"Light ON power available .... Light OFF platform blacked out"
Control room quickly got the message and withdrew their request.
How about a pair of LM34 or similar temperature sensors, one at the AC outlet vent and one in the room or at the inlet vent. Then test that the AC is operating by comparing the two temperature readings.
ethan1701:
I can't hack the AC itself - this is a rented apartment, and I don't want to modify my landlord's AC.
My first idea was to attach a rectified 5V transformer across the compressor and connect the output to a digital pin, but if you can't get at the internals that wouldn't work. Can you put a temp sensor in the A/C output duct and average the reading over a couple of minutes (to avoid spurious readings while it was switching on/off)? That raised another question, though: how are you going to turn the AC on and off from across the room without hacking into it?
What can be done depends on the mechanical setup of the air conditioning system. Is it a simple window unit, or is it an installed hearpump type of system? lack of detailed info means lack of useful suggestions.
The air conditioner is not a window unit, but rather installed on the wall, with the compressor outside the apartment. I intend to control it via an infra red signal, same as the remote control that came with it does.
The volt measuring clamps would probably be too bulky and expensive. Though I like the idea of putting a small fan next to the vent. I think any old fan from an old PC would do the trick. Thanks!
The way industrial units determine if a fan is running is by use of a paddle switch moved by the flowing air. Most simple setup might be a paddle made from a piece of aluminum foil on a piece of cardboard with one wire attached, and the the other wire set so it just touches the aluminum foil on the paddle making a circuit. When air blows on the paddle, the paddle moves away a little breaking the circuit. Buttons on an IR remote control can be operated fairly with a little tinkering like below.
I think that the thing missing here is the difference between the AC being turned on and running. The AC may only be running when it is turned on, but it can be turned on but not currently running.
Unless there is some kind of indicator light that you could monitor, I don't see how you can tell the difference between the AC on but not currently running (the room is cool enough) and the AC not being on.
That's a very valid point. I guess the fan idea just got blown out the window (hehe).
There is in fact an indicator LED I could rely on, and put a photodiode in front of that.
Brainstorm? How about just placing an inexpensive magnetic hall effect sensor on the compressor motor. There should be more then enough magnetic field on when the compressor is actually running Vs when it is not running. That is also a nice non-intrusive measurement that doesn't require an electrical connection to any power circuitry.
Actually current sensing wouldn't be the worst idea seeing as the compressor would draw a measureable amount of current more than when just the fan is blowing.
Also, if this AC unit is anything like mine when the compressor kicks in the thing will vibrate enough that you could couple an accelerometer to the unit to give you detection.
I'm now inclined to glue a small rare earth magnet to the vent, and put a reed switch next to its "open" position, and thus have a circuit close when it's on.
Cr magnetics sells a nice current switch that you can use to sense power going into the compressor or a fan. That's what I have used successfully in the past. They are non contact, just have to lead a line wire through the hole to enable it. Iirc, the minimum current to trip it reliably was 350mA. However, you can always run a wire multiple times through the loop (assuming you have excess available) and hence increase the sensitivity.