How to use a potentiometer resistor to control speed of motor fan manually?Thanks

[mengckid]

Hi Mengckid,

You did't mention which PIC you were using or what application.
Here is code that I use with hardware pwm (HPWM).
My application requires 5 speeds and a 60% minimum speed setting.
You can add more comparisons or calculate speed settings based on AD1.
There are 2 lines that control acceleration & de-acceleration
I like the hardware pwm best, it runs consistent speed
while your program executes other code. It will work with PWM if you change the last line.

ADCIN 1,AD1 'read channel 1...AN1
AD1 = AD1 >> 6 'justify data

ADJUSTFAN:
IF AD1 < 2 then FANSPEED = 153 '60% min speed
IF AD1 >= 3 then SPEED = 178 '70%
IF AD1 >= 5 then SPEED = 204 '80%
IF AD1 >= 7 then SPEED = 229 '90%
IF AD1 >= 9 then SPEED = 255 '100%
IF SPEED > SPD THEN SPD = SPD + 1 'accelerate
IF SPEED < SPD THEN SPD = SPD - 1 'de-accelerate
hpwm 2,SPD,32760 ' PWM 20,000 Hz

Mark

Thanks u,anyway... you are so great,ur code help me much,thanks u

The PIC i am using is PIC16F874A, and the application is used the single turn 10k potentiometer to increase or decrease the speed of motor fan in another pin in PIC. Meaning,i will use a N-channel MOSFET to drive the current to motor fan.

Sorry for that, if I willing to use PWM command to control speed of motor fan, meaning accelerate or de-accelerate it, can I do that?

Hopefully, you can help me, thanks a million

[mister_e]

if I willing to use PWM command to control speed of motor fan, meaning accelerate or de-accelerate it, can I do that?

If you mean PWM instead of HPWM you'll be disapointed, PWM do only few cycle and don't run in background. AND MORE, the signal generated is quite poor. This is really not what you need.

If your PIC don't have any PWM module, you can still use timer interrupt to generate the PWM signal.

HPWM is the way to go. It could be as simple as...

START:
    ADCIN 0,MotorSpeed
    HPWM MotorSpeed
        '
        ' Other code here
        '
    GOTO START

[CocaColaKid]

I have to agree with Mr E, HPWM is definitely the way to go. Once you set it it keeps on running until PWM which needs to be refresh all the time. We use an op-amp with high input impedence along with a small capacitor attached to the IO so that we can do other things with out having to refresh all the time. It's not a smooth an output as the HPWM but it does work. The capacitor slowly discharges through the op-amp.