Smart AC Unit

by littleBits July 15, 2014

Monitor and control the temperature of your home remotely. 

Want a smart air conditioner without having to buy a new one? Retrofit your existing window unit with littleBits and turn it into an internet-connected device. Forget to turn the AC off? No problem, just press a button on your phone to turn it off! Cool down your apartment on the way home from work? Easy! Save energy and save $$$ with this easy DIY project.

*Note: The AC Switch, IR transmitter, and temperature sensor are coming soon. Stay tuned!

How it works:

Monitor - The temperature sensor transmits data through the cloudBit to Cloud Control. You will be able to see the temperature readout in cloud control under the “receive” tab. When at home, you will also be able to see the temperature displayed on the number module. Now you can always know the temperature in your apartment/house.

Control - Use Cloud Control to turn your AC unit on or off using the IR transmitter and the AC switch. When you press the button in Cloud Control, you send a signal to the cloudBit in your home. This signal is passed on to the IR transmitter, which outputs a burst of infrared light. [Note: you won’t be able to see this burst of light because the IR spectrum is not visible to the human eye. This is the same control technology used in your television's remote control]. The AC switch has an infrared sensor that picks up this burst of IR light and toggles the window unit’s power on and off.

Automate - Use IFTTT to automatically turn your AC unit on/off in response to conditions that you set. IFTTT (If This Then That) is a service that lets you connect to different web apps through simple conditional statements. Use the Date & Time channel to turn your AC on at 5pm and off at 8pm, or create a location based trigger that turns your AC unit on when you enter your home zone with the iOS or Android Location channels.

Bits used: cloudBit™, IR Transmitter, number, temperature sensor, usb power

Tags: Wi-Fi Gadgets Hack Around the house

Videos and Recipes

IFTTT Recipe: If I send IFTTT a text tagged #AC, then turn on my Air Conditioner connects sms to littlebits


  1. 1

    Set up your cloudBits if you haven’t done so already. Instructions for setting up the cloudBit can be found here.

  2. 2

    Connect your circuit: USB power + temperature sensor + number + cloudBit + IR transmitter. We held our circuit together with littleBits Adhesive Shoes and mounted it to our AC unit. Set the number module to “value” mode so it will display the temperature data in either fahrenheit or celsius. Switch between the two readouts by flipping the switch on the temperature sensor board.

  3. 3

    Turn on your AC unit and set a desired temperature. While it is still on, unplug it.

  4. 4

    Plug the AC Switch into the wall. Now, plug your AC unit into the AC switch. You will notice that the AC switch has a small oval-shaped sensor tethered to it. You will want to position this sensor so that there is a direct line of sight between it and the IR transmitter on your littleBits circuit.

    Note: the IR transmitter emits light out from the side of the board. You will need to position the circuit so that the side of the IR transmitter is facing the AC switch. IR light is invisible to the human eye so you won't see anything happen on the board when you trigger the IR transmitter.  In our case, we placed the sensor directly below our circuit on the AC unit.

  5. 5

    Prepare the IR transmitter. The IR transmitter has four channels and is able to work with up to four AC switches. However, for this project, unless you have more than one AC switch, you only need to use one channel on the IR transmitter. Set one of the little switches on the IR transmitter to the "on" position.

  6. 6

    Pair the IR Transmitter with the AC switch. If you have a button module handy, temporarily replace the cloudBit in your circuit with it [if not, you can still use the cloudBit - the button just makes it easier to test quickly]. On the AC switch, you will see a slow blinking red light. If you don’t see this, hold down the button on the AC switch until you do. On your circuit, press the button module to pair with the IR transmitter. You should see the red light on the AC switch blink very quickly and then go off.

  7. 7

    Test the circuit. Now, when you press the button module, your AC unit should turn on. Press it again and your AC unit should turn off. If it doesn't work, check all the connections of your plugs and/or try adjusting the positioning of the IR transmitter. To reset the AC switch, just hold the button down until the red light starts blinking slowly again.

  8. 8

    Make it smart! Once you know your circuit works, replace the button module with the cloudBit. Wait for the cloudBit to connect to wifi (the status LED should be solid green), and then use the button on Cloud Control to remotely turn your AC unit on and off.

  9. 9

    Stay cool!

Bits used (5)

Accessories used (3)

Other Materials Used (1)

  • AC window unit 1

Other files

  • phatbhuda 5 months ago

    This is neat, but what I'd really like is the ability to use the IR Transmitter to send IR remote control signals to my AC unit. Paired with the Arduino bit this should be easily doable.

  • monkycl 4 months ago

    Hi, can it work with another IR switch like that?

    • littleBits 4 months ago

      Our IR transmitter is programmed to our own AC switch, so it won't work out of the box with other remote control devices.

  • mzamkow 3 months ago

    Will the IR transmitter be programmable to send different messages? I'd love to be able to pair it with a cloudBit to cloudify all my devices that already have IR sensors built in (TV, stereo, etc)

    • emily_littlebits 3 months ago

      The forthcoming IR transmitter is not re-programmable. It is currently configured to work only with our AC switch and the remote trigger module. Perhaps this will be possible in a future version though :)

  • afro001 23 days ago

    Is it possible to use IFTTT with the information provided by the temp sensor itself, so if the temp rises above X temp, switch on? I'm thinking this would be ideal for heating/cooling a babies room, particularly overnight when you're not checking the control hub.

    • afro001 23 days ago

      Actually, I just noticed the threshold module, but not sure where that would fit into the circuit and if it could be used to also switch off when it reaches a given temp...

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