First thing you need a thermostat to control temp.. otherwise your chicks cannot survive...
second is FAN ... use computer phone with 12v dc power supply to rotate generated bulb heat into bator.
Third.. direct bulb light can harm your eggs. Even you have a temp or hygrometer but direct bulb light can change temp immediately until your meter values changes. In my opinion temp which effects egg will be by air not by direct bulb light.
You cannot hatch until all three conditions must be true.. In my opinion your design is not correct
have a look at my homemade bator.
here you can see bulb is protected by foil.. so when bulb lit its light cannot effect eggs. just below bulb you can see two computers smps fans are situated to rotate heat... you can install only one ( i did it coz my one fan is weaker and i dont want to replace fan during hatching process :) ).
you can see thermostat just beside eggs to control bulb on and off.
Fan must be near water to increase vaporization in the air..
One more thing should remm that eggs and water should be in separate layer otherwise after hatching chicks can drowned their self in to water.
I successfully hatched 4 out of five this weekend in this bator.. :)
Edited by rahul2299 - 5/12/12 at 1:55pm