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Simple 12V DC Fan Speed Controller Circuit

A simple 12V DC fan speed controller is an important circuit that helps control how fast a fan runs by adjusting the voltage.

In this post, we will look at a 12V DC fan speed controller that uses the IC LM2941.

This component is known as a low dropout voltage regulator and can manage up to 1A of current.

It is especially useful in situations where you need to change the fan speed like in cooling systems, temperature control devices and different automation projects.

In the following sections, we will explore how a fan speed controller circuit works with the IC LM2941 focusing on its role as a low dropout adjustable voltage regulator.

Circuit Working:

Parts List:

Component TypeSpecificationQuantity
Resistor2.2k 1/4 Watt1
Potentiometer22k1
Potentiometer10k1
CapacitorCeramic 470nF1
CapacitorElectrolytic 470µF 25V1
SemiconductorIC LM29411
Fan12V DC Fan1

The above circuit diagram shows how the fan speed controller works with the IC LM2941.

The IC LM2941 is a type of voltage regulator that can adjust the output voltage as needed.

In this setup the potentiometers VR1, VR2 and resistor R1 are used to form a voltage divider which is important for setting the output voltage that controls how fast the fan spins.

The circuit gets a 12V DC input to work properly.

To keep everything stable and reduce any changes in the input voltage a capacitor C1 is used.

The LM2941 effectively manages the output voltage based on the resistor values in the feedback loop.

You can find the output voltage at a specific pin using the formula below.

Also, capacitor C2 helps to smooth the output voltage making sure the fan gets a steady power supply.

The fan runs well at this controlled output voltage and its speed can be changed by adjusting the resistor values.

Formulas with Calculations:

Below mentioned are the formulas with calculations for Simple 12V DC Fan Speed Controller Circuit:

Output Voltage Formula:

Vout = Vref × (1 + (VR1 / VR2)) + (Iadj × R1)

where,

Substituting the given resistor values:

Vout = 1.275 × (1 + (22k / 10k))

Vout = 1.275 × (1 + 2.2)

Vout = 1.275 × 3.2

Vout = 4.08V

The fan will run at about 4.08V with these resistor settings.

If you change VR1or VR2 it will alter the output voltage, which means you can control how fast the fan goes.

How to Build:

To build a Simple 12V DC Fan Speed Controller Circuit following steps are needed for connections of the circuit:

Conclusion:

A simple 12V DC fan speed controller that uses the IC LM2941 is an easy and efficient method to control how fast a fan runs by adjusting the voltage.

It is a budget friendly option that requires only a few parts, yet it provides steady and adjustable fan performance.

By changing the resistor values users can fine tune the fan speed making it perfect for different uses like cooling systems and automation projects.

References:

Datasheet IC LM2941

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