How to make Temperature controlled circuit

Temperature controlled home automation

In this project, we are going to make a simple Temperature controlled circuit using Temperature Sensor LM35.This circuit will be automatically on or off your any AC home appliance according to temperature. We also adjust the temperature by the Variable resistor in the circuit. . When you set the Temperature value at fix Temperature (35 Degree Celsius) then temperature goes above 35 Degree Celsius then fan will switch on automatically and if temperature goes below 35 degree fan will be automatically switched off.

 Temperature controlled circuit diagram:-

 Components Required :-

• 12v Battery
• IC 7805
• Temperature sensor LM35
• Op-amp LM358
• 1k ohm Resistor (3)
• 10k ohm Resistor (1)
• 4.7k ohm Resistor (1)
• Variable Resistor 10k
• LEDs (Red and Green)
• NPN Transistor BC547 (1)
• Diode 1N4007
• Relay 12v
• Bulb or any AC appliance
• Capacitor (1000uF and 100uF)

PCB :-

Working:-

In this we are using a 12v general purpose adopter is used to power up the whole circuit and IC7805 is used to provide the regulated 5v supply to the circuit. The Supply is indicating by RED led. When temperature goes below down 35 degree Celsius then “reference voltage >>> LM35 Output voltage” and When temperature is goes above 35 degree Celsius then “LM35 Output voltage >>> reference voltage” and this is compare by Op-amp. LM358. And given Output is High this Output of LM358 connected to the base of NPN transistor BC547 .This BC547 transistor is switch on then after switching the 12v relay     also becomes ON and Green LED starts glowing and AC home applies is automatically switching on.

Temperature Sensor LM35:-

1.     LM35 is an analog temperature sensor.

2.     The LM35 sensor converts temperature values from -55ºC to 150ºC.

3.     The sensor has a sensitivity of 10mV / ^oC

4.     LM35 is Operates from 4 to 30 volts

5.     LM35 is three pin transistors like device. It has VCC, GND and OUTPUT

6.     The LM35 is a low voltage IC which uses approximately +5VDC of power.

Operational Amplifier LM358:-

1.     LM358 is a Dual Low Noise Operational Amplifier which have two Op Amp in a single chip.

2.     LM358 consists of two independent, high-gain, frequency-compensated operational amplifiers designed to operate from a single supply over a wide range of voltages.

3.     LM358 is Dual voltage comparators inside.

4.     This is a general purpose op amp which can be configured in many modes like comparator.

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