Introduction: LittleBitty Air Conditioner

About: Welcome Innovators! Glad you can join me on the journey of Making! The quest began twelve years ago, when I received my first set of Snap Circuits. Since then, I was intrigued with the possibilities of creatio…

Has your room been a little too hot lately? Thinking about having a lemonade stand? A picnic? Prepare for summer with the littleBitty Air Conditioner! There are two options to turn on the Air Conditioner; through a temperature sensor or with the use of the wireless kit.The Arduino bit senses the room/outside temperature and turns on the littleBits fans and the PC fan after a certain temperature is reached. Add ice to the case and enjoy the cold air. Ideal for desks, picnics, table stands at workshops, or for any purposes where cool air is needed. If your vehicle doesn't have cool air then, you have found the right solution! Enjoy music with the wireless remote, too! :)

After viewing a similar project online, I thought it would be awesome to build a mini air conditioner since I had an old computer fan laying around. The Arduino bit has definitely expanded the capabilities of innovation and prototyping! I am excited for the new beginning!


1K resistor (1)

1N4004 Diode (1)

9 volt battery (1)

Breadboard (1)

Case (1)

Double-Sided Tape (1)

Jumper Wires (1)

Mesh (1)

Mounting putty (1)

PC Fan (1)

Screws & Bolts

TIP120 Darlignton Transistor (1)

TMP36 temperature sensor (1)

Wire Cutters (1)



Drill Press

Hot Glue Gun

Soldering Iron & Solder


Arduino Leonardo LittleBit (1)

button (1)

fan (3)

fork (1)

latch (1)

power (2)

split (1)

synth speaker (1)

wire (3)

wireless receiver (1)

wireless transmitter (1)

Step 1: Drilling

Warning: This circuit draws a lot of current through the Power Bit from the fan bits. Keep the power bit connected to the Mounting Board to prevent heat exposure.

The first step is to drill four holes into the plastic case. This step definitely requires adult supervision. I used a small plastic case from an old DC power supply. If you don't have a solid plastic case then a water resistant case or storage case will work as well, just use scissors to cut out the holes. Find the dimensions of your computer fan and trace the outline of the spinning blade on one side of the case. Trace the outline of the three littleBits spinning blades on the other side of the case; or however you want to set up your air flow. Drill holes large enough to accommodate the rotation of the spinning blades.

After drilling the four main holes, align the fans over the holes and ensure that there is enough space for the rotation of the spinning blades. Use a marker to mark the points of the corners of each fan to drill smaller holes to mount the fans. At least drill two holes to mount each fan; excluding the computer fan. The larger fan will require four screws to mount. The littleBits fans should be faced in the way where it sucks the outside air inside of the case. The PC fan should be faced where it blows out the cool air. I drilled a small hole at the bottom of the case to connect a mini tripod.

Step 2: Mesh

Now, lets use the plastic mesh to glue on the inside of the case This will prevent collisions between the ice and the spinning blades. Measure the size of the littleBits fan and the computer fan. Once the measurements are determined, cut the measurements out of the plastic mesh. Glue the mesh pieces to the inside of the plastic container. This will give a cool look to the box!

Step 3: Soldering

Now since the case is finished, we can begin to build the circuit. The first tools and components we will require are the soldering iron, arduino bit, wire snips, and jumper wires. If you do not know how to solder, I recommend watching this tutorial: Solder black jumper wires from pins A3 and D13; these two are our ground wires. Solder a red wire to pin D11; this is our power wire to the temperature sensor. Solder a blue wire to pin A2; this is our analog sensing wire (I used a red wire). Solder a red wire to pin D10; this wire is used to activate the Darlignton transistor to enable the computer fan. Solder a 1k ohm resistor to the end of the wire on pin D10.

Step 4: Circuitry

Lets build the littleBits circuits: Power + Wire + Wireless Receiver + (3rd Channel) Wire Bit + Arduino Bit (pin A0). Other side of Arduino Bit (pin D1) + Wire Bit + Fork + Fan + Fan + Fan. The second circuit is the remote. Power + button + Wireless transmitter (3rd Channel) + speaker (1st Channel).

Step 5: Schematic

Lets move to the component side of the circuit. To Control the 12 Volt computer fan from an arduino input, we will use a temperature sensor and the TMP36 to calculate the temperature of the room. To learn more about this component please visit The pins on the sensor from the flat facing side are the 3.3-5.5 Volt pin (left), analog sensor pin (middle), and the ground pin (left). Use the jumper wires from the Arduino to connect to the temperature sensor in a bread board. Pin D13 connects to the ground pin. Pin A2 connects to the analog pin; this measures the amount of voltage produced by the sensor. Pin D11 connects to the power pin.

In this step we will create a circuit to control the 12 Volt Computer fan from an input of an Arduino pin. We will use the 1N4004 diode, TIP120 Darlignton transistor, jumper wires, 9 Volt battery, and the PC fan. Connect pin A3 to the Emitter pin of the transistor and to the battery's ground. Connect the battery's hot wire (red) to the hot wire of the fan. Connect the ground wire of the fan to the base of the transistor. Connect the striped side of the diode to the Collector pin, as well. Connect the other side of the diode to the Emitter. Connect wire D10 to the Base.

The Darlignton transistor is used to allow the current from the 9 Volt battery to flow to the PC fan from the input of the Arduino pin. The transistor has 3 pins; Base (connects to the Arduino pin D10), Collector (Diode, and fan), and the Emitter (Ground of the battery and arduino). The 5 Volt input on the base will allow current to flow from the collector to the emitter. The resistor connected between the arduino and the transistor is used to protect the Arduino from shorts or failed components. The diode is used to only allow current to flow in one direction; from the battery power lead to the motor.

Step 6: Arduino Code

Update the 'Air Conditioner' code to the IDE . Change the temperature parameter of the tempOn variable to your preference. Upload the code to the Arduino Bit. Squeeze the temperature sensor and test the circuit. Open the serial monitor and view the temperature readings. The blades should be spinning away!

Step 7: Cool Down!

Mount the breadboard and the littleBits mounting board on the case with putty or double-sided tape. Make any necessary adjustments to the wires.

Awesome! You have created your very own air conditioner/fan! Add ice to the inside of the case and you are ready to go! Take it outside with you to sporting events, BBQs, picnics, table stands, desks, or anywhere you want; except the inside of the swimming pool! :) Be careful not to damaged your littleBits from water exposure! Enjoy!

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