There are several incubators on instructables... why create yet another? Because choice is good, and I liked something from each of the others, not one in particular.

My Goals:

Check once/twice a day to rotate eggs
Not spend too much (I had a lot on hand, spent $50 more)
Use skill I have to build
Not be too complicated

Those last two bullet items mean to write some software, which is what I do for a living. I spent about a day to get this done. I also had my 9 year old and my wife helping. Turned into a great family project!

Here are some of the instructables that I got idea's from:

UPDATE: So I did not have enough fresh air entering the incubator. Because of this my eggs did not hatch. If you follow this build, just make sure you add more ventilation than I did.

Step 1: Container & Egg Holder

Tools:

Hole saw
Rasp
Utility knife
Nail gun & compressor
Staple gun

Supplies:

Foam container (Walmart)
Plexiglass (Lowes)
Duct tape (Lowes)
5/8" x 1.5" wood scraps (Wood stakes - Lowes)
Nails
Screen mesh (Lowes)
Staples

Using the hole saw we cut a viewing hole in the top of the container. Using a utility knife I cut a piece of plexiglass a little bigger than the viewing hole. Then traced the plexiglass onto the container and used the utility knife to trip a bit more of the container so the window would sit flush. Duct taped plexiglass into position.

For the egg holder, I used the scrap pieces of wood to make a rectangle tray about the same size as the opening of the foam container. Then stapled the screen to the bottom of the frame. Finally put some slats to be able to divide up the eggs.

I didn't want the egg holder to be on the bottom, but instead suspended. In order to do this, since the container is tapered on the inside, I carved into the styrofoam a tray holder with the utility knife and the rasp on the corners and two long edges.

Step 2: Electronics and Wiring

Tools:

Computer
USB cable
Arduino software
Breadboard
Soldering Iron
Wiring station
PCB holder
Wire cutters/stripers

Supplies:

Arduino (Adafruit)
LCD Shield for Arduino (Adafruit)
DHT-22 Temp & Humidity Sensor (Adafruit)
Sunfounder Relay (Amazon)
Case Fan (Amazon)
Solder
Wire
Wire connectors
Shrink tubing
Light bulb & socket
Old extension cord
Old wall wart/power converter
Power strip

Code: Arduino Egg Incubator on Github

I am not the best with electronics, but I can follow others work and hack through stuff (sounds like my coding as well). The wiring diagram is attached, and should be correct :)

I then got everything working to what I hope are good specs. The LCD gives a readout of the current temp and humidity. Basically if the temp falls below 100 degrees, then I kick on the light, if it goes about 101, I kick it off. Simple. It seems to cycle the light on and off about every minute to two minutes.

The fan is powered on it's own by a 12v wall wart. I added a connection point so that I could install the fan in the incubator without putting in a big hole.

IncubatorWiring.pdf
Download

Step 3: Finishing It All Up

Tools:

Cutters

Supplies:

Felt pads
Piece of wood
Zip ties

I cut a whole in the container for the light socket and all the wires to feed through. I didn't have a nice box to mount the Arduino and relay in, so a tupperware container does the trick for now.

Attached the fan to a piece of wood with zip ties. Put some felt pads between the fan and wood to reduce noise. Was going to glue the wood to the container, but ended up just letting it sit in there.

Finally, used little plastic container to hold some water. Put the tray into the top and was ready to go.

The incubator stays pretty close between 100 and 101.

Things I would/will change: