Last Updated on April 21, 2022 by technoreview85
It is a high-temperature alarm or over-temperature alarm system electronic project.
In this article, I am going to describe how you can make an easy temperature alarm circuit using an operational amplifier IC LM 358.
It is an easy electronic project idea. As a temperature sensor, I will use an NTC thermistor.
You can make this circuit on a breadboard or you can use a perf board.
Working of this project
I am using a thermistor as an analog sensor.
Actually, a thermistor is a resistor & Its value decreases when the temperature is increased.
Generally, the same sensor is used in the 3D printer print bed & hot end to control temperature.
When the thermistor’s value is decreased then the op-amp IC LM 358 output pin 1 becomes high. An active buzzer & a Led are connected to the IC output pin so the LED & buzzer are turned on. Ic pin 3 is an input pin so the thermistor is connected to ic pin 3.
You can control temperature sensitivity using a potentiometer that is connected to the ic pin 2.
What is an operational amplifier?
An operational amplifier or op-amp is an integrated circuit. It has two inputs. One of them is called an inverted pin which is marked as a (-) negative sign and another is called non-inverted pin which is marked (+) positive sign.
It has one output pin.
Its basic work is to amplify and output the voltage difference between the two input pins.
Ic lm358 has two op-amps.it is a dual op-amp Ic.
Applications of this circuit
Over-temperature alarm for industrial purposes. Alarm systems for big electrical appliances,
You can use it as a fire alarm to prevent disasters at the home, office, school etc.
You need to make
- Active Buzzer ( passive buzzer will not work )
- Resistor 1K, 2.2K
- Potentiometer 10K
- Perfboard
- LED
- Ic LM358 & 8 pin Ic base
- 9V Battery & Battery connector
- Thermistor 10K
Project video
Circuit diagram
Spacial connection diagram with practical components
