My temp differance is about 3 degrees. In this one I just have the fan pointed in an upward positon. The nest one I build will have dual fans and be a little better insulated to control the over all temp. After all this one was a test. Total cost of this one was about 30 dollars because I...
I keep two quart mason jars of water and my humidity pan as well to help with the temp. Here are some pics of my incubator and hatcher. I will be making a new incubator because this one was threw together to test my plans.
The last one is what I use as a hatcher.
I a, useing a hot water thermostat at the moment. My temp hold from 97-102. So far all of my eggs are developing correctly. As for a fan how large is your incubator. Also how are you going to tune down your voltage for a PC fan. Most of your Pc fans are 12 volt not 110 volt.