this is what i found that works on dyi bators, I also custom build and educated on the conditioning of air. if you take a dimmer switch hook it up to your light or heat source you can adjust the heat to stay at a constant temp, although you have to adjust on climates, and when building your box you have to have a constant movement of air, so what I have done on previous units I have built and have to explain to people why it takes me upto 4 days to set, is when building your bator you have to know how to adjust your heat to the size of your box. that is where the dimmer switch came into play, i first set up the unit. I dont but the heat light directly on the eggs, I build a partician between the source then drill holes in the partician in the middle. so that the heat will flow up through the holes supplying the eggs with heat, at the back of the unit i place a laptop dual fan these are fairly cheap.what makes them great is the are already in a case and easy to assemble to you unit. i cut a slot the width and length of the fans out, i then drill small hole in front of the unit to allow the air to be circulated back to the bottom of the unit. as the air is being recirculated I have a few holes in front of the bottom panel to draw in fresh air. as the air is being drawn from the top of the unit back to the botton it is coming back across the heat source and wich is keeping a constant temp. now you do have to adjust the heat source and that is why i really recommend the dimmer switch. i have one hooked up to my fans and light, that way in colder months i can decrease the fan speed, and then increase my heat source, then in hotter months I increase fan speed then decrease my heat source. oh and the most important thing i forgot a thermostat from a eletric hot water heater, it serves as a back up to kick off and on your heat source. well I hope that helped anyone, if i lost you or something please let me know i can try to explain.
