Programmable Thermostatic Switch using AD22105

This project simply switches the system OFF or ON whenever the temperature rises at the desired set point.  The desired setpoint can be set using a fixed resistor R6 or PR1 trimmer potentiometer. Use any of at a time R6 or PR1. You can calculate the setpoint resistor R6 using the following equation.

A relay is provided to switch ON or OFF the load. The relay can switch 7Amps/250V AC load. D2 LED indicates the relay operation. J1 provided to choose normally closed or open options for the relay. This project is built using AD22105 IC from Analog devices.  The AD22105 is a single-supply semiconductor thermostat switch that uses circuit architecture to realize the combined functions of a temperature sensor, set point comparator, and output stage all in one IC. By using one external resistor or trimmer pot, the AD22105 can be programmed to switch at any temperature selected by the system designer in the −40°C to +150°C range. The internal comparator is designed to switch accurately as the ambient temperature rises past the set point temperature. When the ambient temperature falls, the comparator relaxes its output at a somewhat lower temperature than that at which the comparator originally switched. The difference between the switch and un-switched temperatures, known as the hysteresis, is nominally 4°C.

Programmable Thermostatic Switch using AD22105 – [Link]

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