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 Type | Specification | Quantity |
|---|---|---|
| Resistor | 2.2k 1/4 Watt | 1 |
| Potentiometer | 22k | 1 |
| Potentiometer | 10k | 1 |
| Capacitor | Ceramic 470nF | 1 |
| Capacitor | Electrolytic 470µF 25V | 1 |
| Semiconductor | IC LM2941 | 1 |
| Fan | 12V DC Fan | 1 |
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,
- Vref is 1.275V reference voltage of IC LM2941
- Iadj is typically small and can be ignored for most calculations
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:
- Assemble all the components mentioned in the above circuit diagram.
- Connect one end of pot VR1 from OUTPUT pin and other end to VR2 pot, and VR2 other end connect to one end of resistor VR1 and other end of VR1 to GND.
- Connect ADJ pin 1 of IC1 between VR2 pot and resistor R1.
- Connect GND pin 3 of IC1 to GND.
- Connect INPUT pin 4 to +12V DC, connect one end of capacitor C1 from input pin and other end of C1 to GND.
- Connect positive of capacitor C2 from OUTPUT pin 5 and negative of capacitor C2 to GND.
- Connect positive of 12V DC to OUTPUT pin 5 and negative of fan to GND.
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.
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