Hi!
Is it possible to control the temperature from an air conditioner using arduino. Or it would be a hard thing to do???
Why not use a relay connected to the Arduino to take the place of the air-conditioner's thermostat? Or just switch the A/C on and off with a relay. You'll need one that is suitably rated for the current and voltage that you'll be switching.
Ok that is the solution for switching off and on.
But setting the temperature for the air conditioner would a hard thing to do?? Or it would be easier to get the thermostat to control the temperature for the air conditioner and interface arduino with thermostat???
Analog or digital thermostat?? What would be easier?? My knowledge about thermostats is null :-/
Thanks
I don't think air-conditioners have a "throttle" that lets you control how much heat they pump out of a room. I think they're either "on" or "off", under control of a thermostat. Do correct me if I'm wrong! So, you'll need a temperature sensor connected to the Arduino, and a relay. Switch on when it's too hot, off when cool.
Our air conditioner has speed and temperature control, so it would be possible to regulate the temperature using those 2 controls without flicking the machine on and off.
I just wouldn't want to be the person trying it, the underside of our A/C is a scary piece of wiring.
Look into the PID library...
So it would be a hard thing to do to interface with the motor of the air conditioner.
So thinking about using the relay...it turns air conditioner to standby or on mode?? So I would have to program the temperature of air conditioner to operate before switching on.
What about relays with an input of 3V and output of 230V I think that is the output..? Any reference??
Driving the the compressor motor (or even just the AC PLUG) with a Solid State relay might be a way... but you need to be careful.
I'd use one of these if I were doing this: --> 25A, 480VAC Solid State Relay, UL
BUT...
I would warn you about cycle time. There is a chance that if you cycle too fast, you will burn out your compressor.
IE: Normal HOME Air Conditioning usually has a cycle time of 10 minutes on/10 minutes off.
You could easily get much more granular and much shorter cycle time... but important note: To avoid straining an air conditioner's compressor, wait at least five minutes between turning it off and turning it back on.
That might not give you the kind of control you want and you may just want to locate your themostat control on the unit... and emulate it.
Thanks for the reply!
Hacking the air conditioner would be a hard thing to do...I even tried to look for the service manual but no luck...
I think I will go for the relay option even though I am limited to switch off and on...
You could use PID if you want to get fancy. If you want to keep it a bit simpler, you could use low speed for temperatures within 1 or 2 degrees of the setting. If it gets outside of that setting you may want to switch to high speed. You may also want to incorporate some timers that would force some hysteresis. Example: once it switches on, it must run for some minimum time. In the same way, once it switches to high, it must run for some minimum time before switching back to low. Your stage-up timer may not be the same as your stage-down timer.
You'll need to decide if you want it to be able to go low-high-low-high and so on, or if you want it to ratchet up from Off to Low to High and then back to Off. Each scenario will require different algorithms for control. You'll also want to make sure that it stays off for a few minutes after it shuts down in order to allow the refrigerant to equalize throughout the system. This protects the compressor from trying to start up under load. Most A/C manufacturers use a 5 minute off timer.
Happy coding!
The vast majority of air conditioners have an on/off circuit for the compressor and a simple "high/medium/low/off" control for the fan. Units with knobs (i.e. no digital electronics) will usually have a knob to control the fan speed (high/low/fan only/off) which will control a 3 speed AC motor for the fan. When that knob is turned on (say "low" for example), the switch closes on a wire that goes to one out of three windings on the motor to give the motor a third of it's total power. The "thermostat" knob uses a simple bimetalic thermal switch adjusted by the knob to switch either on or off depending on the temperature of the air coming into the intake (usually through a copper wire running along the vent behind the filter). This thermostat switch will turn the compressor motor on or off. The compressors don't usually have multiple speeds, but when they do, it's usually set up the same way as the fan motor using seperate windings. Usually, the fan knob will allow you to run with just the fan, or with the compressor on for the full A/C.
Really, all you need is to do is to connect a relay to each motor winding, by activating one winding on the fan motor you get "low", two will get you "medium" and 3 will get you "high". The compressor, like I said, will usually have only one wire (with a common neutral) to turn it on or off and will run the same speed regardless of how fast the fan is running.
Years ago, I actually did this on an air conditioner using a regular digital wall thermostat on my night stand, connected to phone wire to the A/C, this way it would set the temperature at my bed rather than at the A/C. It really wasn't that hard and should be fairly easy with an Arduino (I'm gonna redo that machine with an Arduino later this year when it gets hot enough to use it).
Air conditioners with digital controllers tend to work the same way as their analog counterparts except that they use relays running from a microcontroller. This could make interfacing with the arduino a lot easier if the relays are already there. You could try interfacing with the electronics on the unit, if it's one with a remote control, you could probably even use an IR emitter to control the A/C without modifying the A/C, but what's the fun in that? That would be a lot of work to avoid having to control 4 relays.
I plan to use an arduino at some point to control my A/C for energy savings. I figure that it could monitor a thermistor outside to see if the temperature outside is cooler than the temp setting for inside, if so, it would avoid the compressor and just run the fan with an outside air vent opened by a servo or solenoid. It could also work with a realtime unit to follow a schedule so it stays off while I'm at work and comes on before I get home (like my current one does with the thermometer hack).
Ok then!
Change of path.... I think I will go for the IR way!!!
How to start?? I will look for similar projects...
Thanks
It shouldn't work any different than a regular TV remote. There are tutorials and blog posts out there (I can't think of any off hand, but I'll post some when I find them) that show how to use an IR reciever to record the signals of each button on the existing remote. Once you have all the commands, it's just a matter of programming the Arduino to send out these command signals when needed.