• Skip to main content
  • Skip to secondary menu
  • Skip to primary sidebar
  • Skip to footer
Circuits Gallery

Circuits Gallery

All about Electronics and Circuits

  • Home
  • Basics
    • Components
    • Wiring
    • Circuitry
    • Oscilloscope
    • Conductivity
  • Project
    • Using 555 Timer
    • Using Op-Amp
  • MicroController
    • PIC
  • Arduino
  • Simulation
  • Digital
  • Communication
  • How To
  • About Us

Automatic Temperature Controlled Fan Circuit Using Thermistor

April 30, 2022 by Charles Clark Leave a Comment

This is a simple automatic temperature-controlled fan circuit using an NTC thermistor. The main components of this temp control fan circuit are a negative temperature coefficient thermistor (NTC) which detects the temperature, a comparator which is used to compare the preset temperature value, and a relay circuit to drive the fan. The power supply for this circuit is given by a step-down transformer and a bridge rectifier. A filtering capacitor is used to get the perfect DC. We will be posting a circuit on how to control the fan speed as speed control of the fan is not discussed in this thermistor applications circuit.

Circuit Diagram of Automatic Temperature Control Fan

                                             

Components Required

  1. IC LM324
  2. Transistor BC 548
  3. Diode 1N4007 (4 Nos)
  4. Resistors (1K 2Nos,4.7K)
  5. Variable resistor(10K 2Nos)
  6. Thermistor NTC
  7. Capacitor (1000uF/16V)
  8. Relay 12V
  9. Transformer 230V/0-12,500mA
  10. FAN 230V

Working of Automatic Temperature Controlled Fan

  • The step-down transformer reduces 230V AC into 12V AC. It is then converted into DC by a bridge rectifier circuit. A capacitor (1000uF) is used to avoid unwanted AC ripples.
  • IC LM324 has four comparators each having an inverting and noninverting terminal. Here we use the first comparator, inverting terminal which is connected to a reference voltage made by two voltage divider resistors R1, R2, and a variable resistor RV2.
  • The non-inverting terminal is connected to the thermistor and resistor RV1. The temperature at which the fan becomes ON is set by the variable resistor RV1.
  • When there is a temperature increase, thermistor resistance will decrease as it is a negative temperature coefficient NTC thermistor. Then the voltage drop across RV1 is increased and if it becomes greater than the voltage on the inverting terminal of the comparator, then it output will go high(+Vsat)
  • The high comparator output will turn ON the transistor and the relay will switch ON the fan as a phase of the AC supply is connected to the NO (Normally Open) connection of the relay.
  • When the transistor is ON, the resistors R1 and RV2 become parallel decreasing the voltage drop(reference voltage). Hence fan will not be OFF through the fan ON time the temperature is reached. This difference in temperature can be varied by using the variable resistor RV2.

Components Pin Out

Conclusion

No one likes to left the bed at night when it is too cold. This easy-to-make circuit will help you to automatically control your fan speed as well turning it On and Off depending on the surrounding temperature.

Filed Under: Project, Using Op-Amp

Reader Interactions

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Primary Sidebar

More To See

Oscilloscope versus Vector scope

Oscilloscope versus Vectorscope

Best Oscilloscope for Ham Radio

Best Oscilloscope for Ham Radio – A Comprehensive Guide

3 Pole vs 4 Pole

3 Pole vs 4 Pole | Isolators Compared

Repair Spring Clip Speaker Terminals

Repair Spring Clip Speaker Terminals | A Step-by-Step Guide

More About

  • Arduino
  • Basics
  • Circuitry
  • Communication
  • Components
  • Conductivity
  • Digital
  • How To
  • MicroController
  • Oscilloscope
  • PIC
  • Project
  • Simulation
  • Using 555 Timer
  • Using Op-Amp
  • Wiring

Footer

QUICK LINKS

  • About Us
  • Privacy Policy
  • Terms and Conditions
  • Contact
  • Arduino
  • Basics
  • Circuitry
  • Communication
  • Components
  • Conductivity
  • Digital
  • How To
  • MicroController
  • Oscilloscope
  • PIC
  • Project
  • Simulation
  • Using 555 Timer
  • Using Op-Amp
  • Wiring

AFFILIATE DISCLOSER

Circuits Gallery is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for website owners to earn advertising fees by advertising and linking to amazon (.com, .co.uk, .ca etc) and any other website that may be affiliated with Amazon Service LLC Associates Program

© 2023 · Circuits Gallery | All Rights Reserved