Circuit Schematic Zero Degree Celcius Alarm using Thermistor and LM7215 IC

Eltronicschool. - Thermistor is one electronic component that can detect air temperature that used in many application. One application that we will show to you is to detect temperature for zero degree Celcius like electronic circuit schematic in Figure 1 below. 

Circuit schematic

Figure 1. Circuit Schematic Zero Degree Celcius Alarm using Thermistor and LM7215 IC (Source: Circuitstoday)

Component Parts

1. Thermistor
2. LM7215
3. Resistors
4. Capacitors
5. Transistor
6. All components see in Figure 1 above

Description

Circuit schematic like in Figure 1 above is Circuit Schematic Zero Degree Celcius Alarm using Thermistor and LM7215 IC. According Circuitstoday site describe that this simple circuit will produce an alarm whenever the temperature falls below zero degree. A thermistor is used here to sense temperature. The op-amp LM7215 is used to compare the reference voltage and voltage from the thermistor network. Reference voltage is given to the non inverting input (pin3) of the IC and voltage from thermistor network is given to the inverting input (pin4).When temperature becomes less than zero degree the voltage at the non inverting input becomes larger than the voltage at the inverting input and the output of the op-amp becomes high. This makes the transistor Q1 ON and drives the piezo buzzer to make the alarm. In the power supply section, IC 7805 is used to derive 5V from the 9V battery. Read more here.