On my first hatch i made one from a styrofoam cooler.. It was kind of small but did the job. This time I used a solar panel that we had made last summer, in prep. for the winter on the coops. The spot that our coops are in doesn't get any sun in the winter time so it didn't help much. I took out the aluminum cans and put in the thermostat, bulb, and everything I needed for the bator.
The outside of the box, with some air/vent holes...... The blue light from inside is the fan
Bottom left corner is the light and the thermostat, above that is the hygrometer, and to the right of that is the tray i am using to hold the eggs...It was at temperature so the light had turned off...... all around the inside is foil backed insulation that had been spray painted black when we originally used it for the solar panel. And we used caulking all around to seal it good.
This is the other corner, you can see the bulb has turned back on, the egg tray with a 2nd thermometer, in the center bottom is the bottom of a soda bottle that I am using to hold water to bring up the humidity level, and that blue light on the bottom right corner is the fan circulating the air...