Precise temperature control through Thermoelectric Cooler with PID controller

Avalanche Photo Diode (APD) has wide applications in remote sensing electro optical payloads. APD's gain is highly sensitive to temperature. Hence, temperature of the APD needs to be controlled to get accurate & steady results. This paper proposes a Peltier element based Thermoelectric Cooler (TEC) system for precise temperature control. The design electronics system provides precise control by using PID based close loop system. A commercial available integrated TEC controller MAX1978 is considered for this purpose. This controller provides heating or cooling based on error between set temperature and measured temperature. A negative temperature coefficient (NTC) based Thermistor element is used for temperature measurement. This element is used in a bridge network and provides continuous feedback to controller. Developed electronics is evaluated with simulated load. With hardware test results, short term stability of 70mK is achieved. Peak power drawn by Peltier element is measured nearly 4W.