Minuscule circuit of the
electronic heater controller presented here is built around the
renowned 3-Pin Integrated Temperature Sensor LM35 (IC1) from NSC.
Besides, a popular Bi Mos Op-amp CA3140 (IC2) is used to sense the
status of the temperature sensor IC1, which also controls a solid-state
switch formed by a high power Triac BT136. Resistive type electric heater at the output of T1 turns to ON and to OFF states as instructed by the control circuit.
This gadget can be used as an efficient and safe heater in living
rooms, incubators, heavy electric/electronic instrument etc. Normally,
when the temperature is below a set value (Decided by multi-turn preset
pot P1), voltage at the inverting input (pin2) of IC1 is lower than the
level at the non-inverting terminal (pin3). So, the comparator output
(at pin 6) of IC1 goes high and T1 is triggered to supply mains power to
the desired heater element.