Temperature Controller project using thermistor sensor — analog (Op-Amp) and digital (Arduino PID) designs developed during DRDO internship under Mr. Pankaj Aggarwal (June–July 2025)
A closed loop temperture control can be made using 2 approaches.
- Using a Microcontroller Any microcontroller could be used taken as the primary controll unit. In this prooject, an Arduino was used to sense and regulate temperature using a thermistor as the feedback element.
The microcontroller reads the temperature value(converted from thermistor's resistance), compares it with a referense setpoint, and adjusts the output accordingly using PID control logic.
This output drives the heater or cooling element to maintain the desired temperature precisely.
Key Components
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Arduino Uno
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NTC Thermistor
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MOSFET
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PID controll algorithm
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Potentiometer
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Using an analog Ciruit In this approach, the temperature controller is designed using operational amplifier (op-amp) in Multisim.
The LM-35 sensor is utilised because of its linearly characteristics of temperature with voltage.
The voltage produced form the LM-35 sensor is then compared with a reference voltage using a differential amplifier configuration.
The difference in the voltages is then fed to a PID configuration using 3 op-amps.
The output of the combination of the PID configuration is summed up using a summer and this output is used in a gate driver IC.
Key componenets:
- LM - 35
- Op - amp (LM 741)
- Potentiometer (providing reference voltage)
- Driver IC
- Heater