In this instructable I will show you how to build a small fridge with a peltier cooler. The fridge can cool one aluminium can down to 3 degrees celcius.
For this instructable you need the following material :
- An Arduino - Leonardo Leonardo R3 + USB cable
- A big heatsink with fans
- A smaller heatsink or something to contain an aluminium can
- Thermal past - Arctic Cooling MX-4 4g Thermal Compound
- Temparatur sensor Adafruit TMP36
- 12v Peltier cooler - TEC1-12706 Peltier element 12v 5.8A
- N Channel MOSFET with heat sink
- Resistors (10kOhm and 100kOhm)
- 10kOhm variable resistor
- Some carboard
- 12v 5A Power supply - 60W Transformer UK 3-prong
If you want to build a PCB you also need :
- Pin header connectors
- Screw connectors
- Jumpers or cable
If you don't want to build the circuit on a PCB you need :
You can find the most material on used electronic devices. My heat sinks and fans for example are from CPU coolers.
Step 1: Assemble Cooler
Take the big heatsink and attache a fan. After that put a bit of thermal past on the back side of the peltier cooler and press the module on the heatsink. Finally put the smaller heat sink on top of the peltier cooler with thermal past. You may also want to put a piece of carboard between the two heatsinks to insulate. I also add tape at the side on the heat sink to optimise airflow, but I'm not sure if it's helpeful.
Step 2: Build Circuit
To control the fridge we need an arduino and some electronics. I built a circuit on an experimental stripboard PCB, but you can build it on a breadboard if you don't have a soldering iron.
To avoid bad connections I put a piece of tape at the bottom of the MOSFET heatsink. I added copper wire to some copper strips on the PCB to avoid overheatink
The last picture shows the diagram of the upper side of the PCB. Each
circle is a hole in the PCB and each cross an interuption in the copper strip.
The circuit assume that the arduino is powered by the USB cable of another external power source (not the 12 volt). You can change the circuit and add a voltage regulator or a DC - DC converter to step down the 12 volts to 5 volts.
Step 3: Programming
After the hardware is done, let's start programming. For this you need to download the arduino software.
Copy and past the following code in the editor : https://github.com/postronium/peltier-fridge/blob... .
Befor uploading your code select the right connector in "tool -> port" and select the correct arduino board in "tool -> board".
Explanation of the code
The code reads the voltage at the A1 pin. This voltage represents the target temperature. If the target temperature is lower than the temperature at the sensor, the pulse width is set a bit bigger. If the target temp is bigger that the temperature at the sensor, the pulse width is decreased.
Step 4: Connections
Connect the power on the right connector, there are 4 connectors to connect the fans. Connect the peltier module on the left.The red wire is the "+" and the other the "-". If, for one reason the module work in reverse (get hot where it schould be cooled) you can reverse the polarity.
Solder wires on the "Adafruit TMP36" sensor and connect them to the 3 connector on the PCB.
Step 5: Usage and Safety
Plug the module in the Arduino and connect all the wire, be sure to have wire and a power supply that can provide at least 4 amps. If you built the circuit on a breadboard with jumper wire you shouldn't draw more than 1 amp of current.
Be sure to don't go over the Peltier module current limit. This limit is something about 5 or 6 amps for most of the 12 volt modules.
You can see the Arduino log message with the Arduino software. Go to "tool" -> "serial monitor" in the Arduino software to see it. (see picture)
To cool the hot heat sink efficiently let some space between it and other objects in order to have an optimal airflow.
Be careful short circuits and overheating can hapen, use a power supply with short circuit protection.
I'm not responsable for any damage or incident in any case.
Thank you for reading ! Feel free to ask questions or suggest improvements in the comments section below.