Here a schematic of a really simple electronic thermostat using IC LM56. LM56 is a terribly correct twin output low power thermostat from National Semiconductors.LM56 has varied helpful options like internal temperature sensor, 2 internal voltage comparators, internal voltage reference etc. 2 stable temperature trip points (VT1 and VT2) are created by dividing the LM56′s 1.250V internal voltage reference using 3 external resistors (R1, R2 and R3). There are 2 digital outputs for LM56 .Output1 becomes LOW when the temperature will increase higher than T1 and goes HIGH when the temperature decreases below (T1±Hysteresis Temperature). within the same method, Output2 becomes low when the temperature goes on top of T2 and goes HIGH when the temperature goes below (T2±Hysteresis Temperature).
By connecting a cooler because the load for relay L1 and a heater as the load for relay L2, a really easy and helpful temperature control system will be created.
- The circuit can be assembled on a Vero board.
- Use 5V DC for powering the circuit.
- L1 and L2 can be 5V relays.Their current ratings must be selected according to the load they switch.
- Do not give more than 10V to LM56.
