Cooling Fan speed control circuit

Last Updated on March 16, 2024

As a Electronic engineer we know the importance of proper heat dissipation from the electronic device and system, almost all Electronic components generate heat during operation, and excessive heat can lead to performance degradation and even permanent damage due thermal run away. Cooling fan speed control circuits play a crucial role in maintaining an optimal operating temperature for electronic devices. By adjusting the fan speed based on the temperature, these circuits ensure efficient heat dissipation without unnecessary noise or power consumption.     

This circuit is designed to control small cooling fan (any size that operates in 12V supply), speed of the fan is controlled by the NTC (Negative Temperature Coefficient) thermistors, NTC thermistor Resistance between two terminal will decrease when temperature around it increase.

Circuit diagram for fan speed control

fan speed control circuit

Components List

  1. NTC thermistor 470Ω = 4
  2. Resistor 1KΩ = 2, 390Ω, 10Ω = 4, 1Ω = 1
  3. LED = 2
  4. Capacitor 100μF/25V
  5. DC 12V 4010 Cooling Fan

Construction and Working

Construction and operation of this Circuit is very simple, Power supply to the 12V DC Fan is provided through Four parallelly connected 470Ω NTC Thermistor, Hence the total Resistance with out any sensing range temperature is 117.50Ω, in this situation DC fan receives limited voltage and during the operation of electronic device or system surround temperature will increase and the resistance of thermistor will decrease so the DC Fan gets full voltage. At the full voltage we can expect full speed operation., (This circuit trying to control the speed of DC fan through controlling the voltage and current flow, When you need reliable speed control then this circuit is not recommended try PWM based speed control circuit.)

   In this circuit power supply to the  cooling fan given through four NTC thermistors. Each one have 470Ω resistance when the temperature increase this NTC gives low resistance to the power supply flow to the fan, hence the fan speed increase, by the way the speed of fan controlled automatically depends on temperature.


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