this is a simple automated incubator made using a 555 and comparator ic's. The 7 ohm resistor on the right represents a 10D-9 thermistor that varies its resistance with change in temperature. The other 7 ohm resistor on the left sets a reference voltage at which the output of the comparator is high which then triggers the 555 to switch the relay and power on the infrared lamp. The lamp stays on until the rising temperature of the enclosure drops the thermistor resistance below the value of the reference resistor. Changing the value of the 7 ohm reference resistor changes the temperature at which the light is switched on or off.
Note: The thermistors resistance is inverse to change in temperature.
