Temperature-controlling circuit


Posted on Apr 29, 2012

The circuit switches the current to an electrical heater on and off to maintain the temperature of a room at 25 ±0.5°C. The temperature sensor is a thermistor which provides a differential input (for reduced noise) to an operational amplifier. A 5 kilohm potentiometer is used to adjust the set point through a voltage divider; a value of 2.17 kilohms yields the 25° C setting. A second operational amplifier is connected as an inverting differential-input comparator. The output of operational amplifier 2 controls the electrical heater through a zero-crossing solid-state relay.


Temperature-controlling circuit
Click here to download the full size of the above Circuit.

A transistor/transistor-logic (TTL) gate adjusts the output to the proper level for the relay. A thermal switch is placed in series with the heater and the ac supply for safety in case of thermal runaway. A third operational amplifier monitors the output of the thermistor, providing a signal to a computer for data logging.




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Arc Welder Simulator
Universal Audio Line Amplifier
Switch-Mode Voltage Regulator
Understanding circuit diagram on datasheet and resistor value
Traffic Light Control Circuit
Three Phase 6 Pulse Inverter
50w audio amplifier using ic tda1562
Trimless IF VCO: Part 2: New ICs Simplify Implementation
Infinity Bug
MICROPOWER RADIOACTIVE RADIATION DETECTOR
Current Limiter - Support Material



Top