A few months back my son told me he wanted an ant farm. So after some research and help from AntsCanada we got our first queen ant. The ant colony is doing good but it is time to let them hibernate and that is where the Arduino mini-fridge comes in.
When doing research I seen lots of people suggest using a wine cooler. They do not get as cold as a refrigerator. But those things are expensive. I did not want to spend $100+ on a colony of 6 ants.
That’s when I remembered I had a tiny mini-fridge at work I could repurpose and use to hibernate our ants for a few months. Assuming I could control the temperature.
Arduino Mini-Fridge Parts List
I did not want to damage my mini-fridge so most of the parts are on the outside.
You will need:
- Arduino Uno or some other microcontroller.
- jumper wires. (I like to pull wires out of old network cables.)
- DS18B20 Temperature sensor (Or another kind you like)
- Relay Switch
- an extention cable that you can destroy.
- LCD Screen (optional)
- 3D printer (optional)
Temperature Sensor Test
Here I am testing the temperature sensor with a known good source. I want to make sure everything is set up right and that I have no bugs in my code.
I will link to the code below.
Relay Switch Test
This is where I hooked up the relay switch. I wanted to make sure everything worked right before I enclosed the relay in a box. I also added an LED on the breadboard so I could see when the relay should be on and off.
Then I started working on a box to put the relay in. I will put a download link to this box below in case you are using the same relay switch as me.
Wiring up the Relay Switch
Next, I put the relay switch in line with an extension cable.
DO NOT HAVE THE EXTENSION CABLE PLUGGED INTO THE WALL WHILE WORKING ON IT!
If you do not use a 3D printed box then find some other none conductive box to put it in. This is the most dangerous part and IT COULD KILL YOU if you touch live AC power. Please be very very careful!!!
I 3D printed this box and coated the bottom of it with electrical tape. Then I cut the cable and pulled the wires in. I soldered together the two sets of wires that were not going into the relay so that they would not slide out. Then I wrapped each one real good with electrical tape.
Then I took the neutral wire and hooked it to the relay’s default open connection. This why power would be off by default.
This wire color code chart might help you. https://www.allaboutcircuits.com/textbook/reference/chpt-2/wiring-color-codes-infographic/
Ones that was done I used lots of hot glue to make sure everything was secure and safe. Then I popped the lid on to the box so nothing could be touched by mistake.
The last thing I want is for a pet or my 5-year-old to start poking at it.
All hooked up
Now I plug the mini-fridge into the extension cord I just made and tuck the temperature sensor into the door.
I had soldered the temperature sensor to some long wires I pulled out of a network cable. I was worried it may mess up the reading being at the end of long wires. But it seems to work fine behind 3-4 feet of wire.
Arduino Mini-Fridge In Action
WARNING: This project deals with high voltage AC power. Do not attempt if you are not sure what you are doing.
This project and information is intended for general information purposes only. You should not rely upon this information alone.
By using this information you agree that I have no responsibility for what happens as a result.
AC power can kill you! Please be very careful!
The Code and 3D Print File
Here is a Zip file with the Arduino code and the 3D print file for the relay box.