Mini-fridge to Incubator Project

Discussion in 'Incubating & Hatching Eggs' started by jclaudii, Mar 22, 2017.

  1. jclaudii

    jclaudii Just Hatched

    Feb 27, 2017
    After being unhappy with off the shelf Styrofoam incubators and seeing gpop's awesome wine cooler incubators I finally decided to try build my own. I did have a dorm fridge that I rescued out of the dumpster a year ago and my wife has been threatening to put it back in there, perhaps with me, if I don't do something with it. So here is what I came up with and a bit about how I got to this point.


    The first step was to clean and remove the compressor and a few other pieces that I did not think I would need. The I left the electrical plug but just capped off where the compressor went to the thermostat so I could still use that wiring that is already ran and it allowed the door light to still function :) One of the lines I cut on the compressor went to where the freezer section or Ice Tray area of the fridge. I just pulled some clips out and out the whole cooling coil assembly came. Now I didn't throw this away as It was going to be used to mount a fan and a heating element. The heating element is 40W I believe.


    For some of the "Spare Parts" I scavenged from my old microwave that was on the trailer to be taken to the scrap yard. This is the fan that you hear and makes so much noise when you turn the microwave on. The heating element is from one of the Styrofoam incubators where the thermostat went out. I just used the dremel tool to cut off excess plastic on the fan housing and used it as well to drill some holes in the freezer coils to mount everything too.

    The next step was to be able to see into the darn thing. So I did some measuring.

    Next, I used the dremel to get things started. I broke several of the cheap little blades in trying to cut through this sheet metal front. Safety Glasses are a MUST!

    I then switched to a drillbit

    And attempted to guess where my cut would be.

    This allowed me to break out the big toys. Basically I repeated the process for each of the 4 cuts. I would use the dremel to cut the front sheet metal so the blade could fit in and I would use the drill bit on the dremel to remove some plasstic on the back end so the blade could come out.

    It does make a mess!

    And we end up with this and are ready to silicone it in place. I used whatever I had handy for weight to make the plexi glass press into the silicone.

    Next up was some of the wiring.


    if you look by the light you can see the temp probe dangling. It will be secured better in the future but I didn't want to attach it to the wall.

    I'm using an SSR Solid State Relay for controlling the element. The relay is all digital with no moving parts, will last hundreds of thousands of cycles with silent operation. It is rated at 50 amp and 250v if I wanted to use some massive elements. To turn it on I simply just send it a signal that is between 3 and 32vdc. That signal could be from a ebay PID temp controller, digital thermostat, or in my case an Arduino Micro-controller. Right now the only plugs I have to plug in are the 9v power adapter for the Arduino and the Fridge plug itself.

    It is messy as it's still on a breadboard. But it only has two inputs and one output. Three temp sensors will be in the final design. Two will be in the unit for failover and error checking and one will just tell me what the temp is outside the box. The output simply turns the relay on or off.

    You can barley make out the readings. Temp A: is the Probe inside the incubator and Temp B: is the probe outside. The glowing green light is just an LED on the breadboard that lets me know when power is being sent to the relay. The S: on the second line is the set temp. I still need to make my buttons able to adjust the set temp but for now it is fine being hard coded.

    The relay also has a led that lights up when it is activated :)

    So far it has managed to keep temp stable at 99.5 to 98.5 for a very very short amount of time. Humidity is the hard one to control at the moment. I have on order a ultrasonic misting fogger that should help keep it more stable and it can be activated by a mechanical relay to activate in the future. I still need to add a section to the code that can turn off the heater and flash a light in the case of a data signal issue. This simply means a wire came unhooked and only shows 32 degrees. Which turns the heater on and well it got up to 118 and stayed there not getting any hotter.

    The LCD also has buttons on it and I am using those buttons to switch to another LCD view that shows the Min and Max temp since I reset it. Another button is used to reset the numbers. This is very handy for monitoring temp stability. That way when I have the door open and the temp drops to 84 or whatever and when it reaches 98.5 again I can hit the reset button and it then sets the high as 98.5 and the low as 98.5. From that point on it will overwrite the values as they are replaced.

    My wife just put eggs in it and we will see how it does while I hash out a egg turner ideas. I'll get some pics soon of it with eggs and running. I am working on a version 2.0 that will use a wemos R1 D2 board that is compatible to an Arduino but has built in wifi. The cool thing about that board is I can flash program it while it is running wirelessly AND I can use it to send temperature data to a file so I can render it on a webpage or program. Technically it would be able to send SMS messages if something goes crazy.

    Thanks for looking at my project and I look forward to your feedback. I'll clean my code up and provide it here as well. Big thanks to gpop1 for helping out with the code. I originally tried to do a PID approach but just could not figure it out. It is currently a simple if statement to turn the heater on and off.
  2. eggbert420

    eggbert420 Chillin' With My Peeps

    Feb 15, 2017
  3. gpop1

    gpop1 Chillin' With My Peeps

    May 2, 2015
    I really like it.

    My only concern is the solid state relay can fail shut and that's bad news (been there done that) I suggest either adding a back up standard relay set 1.5 degrees hotter (turns off at 101 degrees and sets off a alarm) or send me a private mail and I will post you a industrial quality solid state relay.

    Ive never tried it but I think you can just connect a analog output to the solid state relay (analog is really a pulse width modulating signal on the arduino) and you should end up with a adjustable heater. Im still not sure there would be a advantage to using a pid but it might be fun to try.

    Drop me a line if you need any help with the code.

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