The circuit diagram given here is a 12V DC Fan speed controller. This circuit is base on the IC LM 2941CT. This IC is 1A voltage regulator IC with low drop out. The drop out of this IC is less than 0.5. This IC can sink a maximum output current of 1A. A 12V DC supply is used for powering this circuit. The IC LM 2941CT has some advanced features like power supply reverse protection, thermal protection, short circuit protection etc. This IC can provide a maximum output current of 1A.
The speed of fan is controlled by using current called adjust current (Iadj) which is determined by the potentiometers R1 (22K), R2 (10K). The 12V DC voltage is applied between Vin (pin4) of the IC and ground pin. The output is taken from Vout (pin5). The fan is connected between Vout and ground. Potentiometer R2 can be used to adjust Iadj, and then the output voltage also changes. By the effect of this fan speed is controlled.
- Use a good quality PCB to assemble this circuit.
- Adequate heat sink should be provided for IC LM 2941CT.
- Minimum fan speed can be adjusted by using potentiometer R1.