Over Heat Detector with Auto Cut-Off System using Op-Amp

Overview: Over Heat Detector with Auto Cut-Off System using Op-Amp

In this mini electronics project, we will build a simple Over Heat Detector with Auto Cut-Off System using Dual Op-Amp IC LM358. The circuit can also be called a Heat Sensor. The circuit basically triggers an alarm or turns on the LED when the temperature of the surrounding rises and goes beyond the desired level. The circuit can help to completely shut down the working system after over heat is sensed.

The usage of the Over Heat Detector circuit is inside your PC or in your kitchen. In an oven, it is desired that does not exceed a maximum temperature and prevent anything from burning. Similarly in a cooling system for perishable foods, it is desired that the temperature does not exceed a maximum level. Heat sensor circuit or Over Heat Detector Circuit senses the heat from various electronic devices like amplifiers, computer and thus generates the warning alarm.

The circuit has an output relay. This relay can connect to any system to warn of an emergency. This could be a sound device, a light source of any other indicator. The relay can also trigger a system to disconnect the heat source. This project for the over heat detector uses a 10K NTC thermistor. NTC thermistors are often the preferred choice for temperature sensing because of their small package sizes and attractive price-performance ratios.

Components Required

Following are the components required for making the project. All the components can be easily purchased from Amazon.

Over Heat Detector Circuit

The circuit diagram of the Over Heat detector is shown below. It is built using an NTC Thermistor, popular Dual Op-Amp LM358, 12V, 1C/O relay, and a few other components.

The NTC Thermistor along with Op-Amp LM358 has been used here for sensing temperature variations. At room temperature, thermistor resistance is around 10K. But when the temperature increases, the thermistor’s resistance becomes low and the output of LM358 becomes high. Consequently, the NPN transistor conducts and activates the Relay.

For testing the circuit you can introduce the hot Iron near thermistor to check whether its working or not. Similarly, you can rotate the Potentiometer to adjust the sensitivity of the Sensor.

You can also check this project Based on Op-Amp IC LM358: Mobile Phone Detector.