In this slide you can know about the circuit diagram and working principle of automatic temperature control system.

1. Electrical and Electronic Shop
Practice.
EEE 2206
Salma Akter
BKH1717032F
Session:2016-17

2. Project Name
Temperature Controlled Automatic DC
Fan.

3. Introduction
A Temperature Controlled System is a type of
control system that automatically controls the
temperature of an object. We commonly
use temperature control systems in Air
Conditioners, Refrigerators, geysers, etc. where the
temperature is automatically adjusted as per the input
settings.

4. Components Required
1. Temperature Sensor LM35
2. Op-Amp IC (LM324/741)
3. Motor Driver IC L293D
4. Potentiometer-10k
5. DC Toy motor
6. Propeller
7. 7805 Voltage Regulator
8. 100uF Capacitor
9. Multi-meter (Digital one is Preferred)
10. A Breadboard

5. Circuit diagram

7. LM324N Pin Outs

9. Working principle:
Initially, at room temperature, V1(voltage of temperature sensor at
room temperature) < V2 (adjusted voltage using potentiometer)and
hence the output of the comparator is low so the motor
is in OFF state.
When heat is applied on the temperature sensor using,
the output voltage of the sensor V1 gradually increases.
This generates a feedback signal. When the output
voltage of sensor V1 exceeds the reference voltage V2
set by the pot, the comparator’s output goes high and
hence turns ON the motor through the motor driver.

10. When the motor turns ON, It produces high velocity wind
and blows. Now since the heat source is turned OFF, the
temperature sensor starts cooling and there by its output
voltage V1 reduces gradually. When V1 falls below the
reference voltage V2, the comparator’s output again
goes low and hence turns off the motor.

12. Applications
 The Temperature Control System is a common type
control system implemented in different types of
systems like Air Conditioning, Water Heaters,
Refrigerators, etc.
 This type of Temperature Controlled Systems can also
be implemented in industries, automobiles.

13. Advantages of this circuit:
1. No complex circuitry.
2. Cheap
3. No need of any advanced programming
or Microcontrollers.

14. Thank You.