A brief outline for a homemade, autoturning incubator that can be left over long periods (say if I go away for the weekend). In practice I suspect pretty low hatch rates will result from all of the bumping about that the eggs are subjected to.
MICROWAVE OVENS ARE HIGH VOLTAGE ELECTRIC APPLIANCES.
I DO NOT ADVISE ATTEMPTING TO MODIFY A MICROWAVE OVEN.
Step 1. Unplug the microwave oven and gut the electrics. Junk the magnetron, the big transformer, and the big capacitor. Leave most of the other stuff in, especially the turntable motor and whatever else is required to power it up. It will serve as the motor for the egg turner. Save the glass turntable plate too.
- This is a very dangerous procedure if you don't know what you're doing. You can kill yourself on the high voltage capacitor even if the microwave is not plugged in. The first thing you must do after taking the back of the microwave off is to identify the large oval-shaped metal tube and discharge it by grounding the terminals to the chassis using a suitable tool.
Step 2. Make a rotary egg turner that straddles the turntable plate. Arrange it so that it stands on the floor in a fixed position while the turntable spins at 5 RPM or so. Maybe put a textured rubber mat on top of the plate as a shock absorber, and to ensure that the eggs spin rather than skid. As the turntable spins, the eggs turn. The fact that the turntable spins in a random direction each time you turn it on is actually a useful design feature here.
Step 3. Now the microwave contains everything that you need to rig up an electronic timer. You press the button, the egg turner rotates for a while, and then it goes Ping! and stops. Kinda fun and you don't need to open the door. Even better is to make an automatic timer that turns the turntable on for 10 seconds or so every hour while you drink beer and watch TV. This site gives an idea of how to do it. You will need a low voltage power supply for it: there may already be one inside if the microwave has an electronic timer and push button interface, rather than the old style power and time dials. You will need a mains relay on the output: try using the one in the microwave guts. Protect the live wire with a fuse. The one that is already in the microwave probably has too high a rating.
Step 4. Make an electronic thermostat and connect it to two 12V 10W long life halogen bulbs and a 12V CPU fan like this. Power it using the same source that you used for the timer. Mount the lamps, fan, and temperature probe inside the main compartment of the microwave. (As an alternative to a CPU fan, you might be able to use the mains fan that is already inside the microwave. The main problem is that you need a fan that will circulate air gently around the interior, but the microwave fan is designed to blast cool air on the magnetron to stop it overheating. It will likely haul out all the heat and humidity. There will also be a little light bulb in there but it is probably too small and food-spattered to be useful. Although I suppose you could try to reuse the light fitting.)
Step 5. Make sure that the microwave casing is earthed. Check that the mains live wire is connected through a fuse and that the fuse has an appropriate current rating. Double check the electrics to make sure everything is safe. If you are not sure, ask a qualified electrician to have a look at it.
- Is it safe? Are you sure?
Block off some of the air holes to the interior compartment. Then cover round with insulation to retain warmth. Duct tape is good.
Step 6. Twiddle with your homemade turner and thermostat until you are happy with it. Plug in the mains. Put eggs in the turner and throw your thermometers, a hygrometer, and damp sponges/diapers for humidity. Leave for 18 days, topping up the humidity as necessary. Switch off turner for lockdown. Hatch eggs, remove chicks to brooder. Bada bing.
Click here to see the build.