Just though I'd share this after a poor experience with last hatch. My main gripes last time were not enough room for eggs and the light bulb went pop on day 18.
So the basis of it is a cool box, I brought for 5 pounds from as supermarket. The window is 2 CD cases cut in glued with silicone sealant and lots of fashing tape
Here is the "Control unit" using an unused guitar pedal case going spare. I have a fairly standard Veleman MK138 kit with a couple of mods as per recommended to make the range suitable for incubation, higher temps and low hysterisis
R4 4K7, R5 3k9 ,R6 2K7 ,R7 2M (should be 10M but I had none of those, makes very little difference in the real world RV1 1K Pot
Holds the temperature accurately and 37.5 Deg C is the centre of my control dial.
On the back, 12V input, Sensor input, Heater output, Lamp output (there is a toggle to turn the light on and off, will put in some LEDs to make light it up)
My heater is made from a canibalised dead computer power supply. I ripped it apart and threw away the inards and kept the case and fan only
Inside the PSU case I have put an elecrican's junction box and 2 coils of nichrome wire approximately 1 Metre each, both wired across 12v.
I think the nichrome wire I had was 24SWG, each meter is about 5 ohms, giving 2.5 ohms with both wired in parallel. The wire gets warm but not super hot, and as the air drawn by the fan blows it around the incubator.
I found the fan a bit fierce at first, so I slowed it down a little with a series resistor (100ohm)
Then my spindle turner, based around a motor for a glitter ball
The glitter ball motor, with "mechanically questonable" linkages - they look awful but actually work quite well..
The spindle and the perspex tray. I'm hatching bantam eggs so I've used 22x 32mm holes cut with a wood bit., which are fine but I recon 35 would be perfect - I wish I had an arbour drill it might have come out neater.
I found some wingnuts to make disassembly for cleaning less of a chore.
There you have it - here we go with the next batch. Fingers crossed nothing breaks.