discussion the Automatic Fan Speed using Temperature (LM35)

[yonghui]

when u manual turn the preset, the preset output voltage value will change, so PIC can read the voltage through the ADC channel.
then u can control the fan speed by using PWM pulse. PWM's duty cycle can be controlled, to get the fan speed.

i dont understand those transistors network part there. and i dont see how u can make PWM pulse from the transistors there.

[vitor85]

actually that part is my pwm circuit to control the fan speed.can you help me to explain the circuit working?thank you!

[vitor85]

thank you explain!can you help me to explain the circuit on below:

[yonghui]

whre did u get that "PWM" circuit from? can u explain how it work?