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

[mengckid]

Hi Mengckid,

Your Pic has the hardware PWM built-in so it is your best choice.
Your program can read the ADC (pot) and update the speed variable
and the hardware PWM does the rest.
Depending on your motor voltage & current draw you may need to
consider your Mosfet circuit. Your Mosfet's voltage rating should be
at least twice your DC supply voltage. You need a clamp diode connected
across your motor (cathode to M+ anode to M-).
Your Mosfet has 2 losses that generate heat, conduction loss (dc current squared times the rds on resistance). example 2 Amps x 2 Amps x .1 ohm = .4 watts, requiring a heat sink. The Mosfet has a large gate capacitance that can give slow turn on & turn off times (switching losses). I prefer to use a mosfet driver IC such as TC4426 or TC4427.

Mark

HiHi,yaya, thanks u again

i got few problem here:

for the code above, I cannot compile this part: The code:
IF SPEED > SPD THEN SPD = SPD + 1 'accelerate
IF SPEED < SPD THEN SPD = SPD - 1 'de-accelerate

the error message is mismatching if loop..then...endif. Thus, i dunno how to fixed it. Thus, here is my code, hopefully you can help me a bit, thanks ya


INCLUDE "modedefs.bas"
DEFINE OSC 4

DEFINE ADC_BITS 8 ' Set number of bits in result
DEFINE ADC_CLOCK 3 ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 10 ' Set sampling time in microseconds
AD1 var byte
SPEED var byte
SPD var byte

TRISB = %10000000 ' set output for led portb.0
TRISC = %11111000 ' set output for pwm portc.2
TRISA = %111111 ' Set PORTA to all input

ADCON1 = 0 ' for 10-bit ADC and Set all PORTA is analog
ADCON0 =%10000101 'SET A/D Fosc/32, [4MHz], CHANNEL-0 = ON

main:

ADCIN 0,AD1 'read chanel 1...AN1
AD1 = AD1 >> 6 'justify data
gosub ADJUSTFAN
hpwm 2,SPD,300 ' PWM 20,000 Hz

IF SPEED > SPD THEN goto acce
endif
if speed <= SPD then goto deacce
endif

ADJUSTFAN:

IF AD1 < 2 then
SPEED = 153
endif '60% min speed
IF AD1 >= 3 then
SPEED = 178
endif '70%
IF AD1 >= 5 then
SPEED = 204
endif '80%
IF AD1 >= 7 then
SPEED = 229
endif '90%
IF AD1 >= 9 then
SPEED = 255
endif '100%
return

acce: SPD = SPD + 1 'accelerate
hpwm 2,SPD,300
return

deacce: SPD = SPD - 1 'de-accelerate
hpwm 2,SPD,300
return

P/s : The code above is Pic Basic Pro code...


Another problem is how do I get the ADC scaling. Actually, what is ADC scaling mean?? If I wanna do the ADC scaling from 1-32, so how to write in pic basic code? Is it neccessary to iniatiate first, the 1-32 values?

Thanks u,cheers

Regards
Mengckid

[mengckid]

I need some helps~~Can anybody tell me how to scale ADC or ADC scaling meaning if i wanna scale a voltage value from 0V to 5V in ADC Scaling from 1-32 values? How to do that?

In Pic Basic Pro, Do I need to initiate the ADC scaling 1-32 values? like assembely language.

If I wanna do a increasing speed or decreasing speed continuesly, i wanna create a mathematical equations Pic Basic Pro?Can I...anyone got any ideas,can share here....hehe,thanks a million...I really need a help here,thanks you

[mister_e]

a range from 0-32!!

if you use a 10Bit resolution

Adcin 0,Initial
Final=Initial>>5

change 5 for 3 if you use a 8 bit resolution.

32= 2^5 or 5 bit resolution

Im i still mixed in my head... maybe, as now, it looks good to me.

10 bit resolution = range of 1024
8 bit resolution = range of 256

1024/32 =>32
256/32 =>8

and blah blah blah... i feel like a pre-school teacher today

[mengckid]

Hi...I need some helps here...once again,i will post my Pic Basic Pro Code below,hopefully somebody will help me fixed my code, bcoz i just cant get the result that i want...

The Code:

include "modedefs.bas"
DEFINE OSC 4

' Define ADCIN parameters
DEFINE ADC_BITS 8 ' Set number of bits in result
DEFINE ADC_CLOCK 3 ' Set clock source (rc = 3)
DEFINE ADC_SAMPLEUS 10 ' Set sampling time in microseconds

B0 var BYTE ' Create B0 to store result

TRISB = %10000000 ' set output for led portb.0
TRISC = %11111000 ' set output for pwm portc.2
TRISA = %111111 ' Set PORTA to all input

CCP1CON = %00001100 ' Set CCP1 to PWM
ADCON1 = 0 ' for 10-bit ADC and Set all PORTA is analog

HIGH PORTB.0

GOSUB GETMBAT 'read voltage variable
main:

ADCIN 0,B0 ' Read channel 0 to B0
B0 = B0 >> 3 'justify data

if (B0>0) and (B0<5) THEN
PWM PORTC.1,10,100
endif
if (B0>5) and (B0<10) THEN
PWM PORTC.1,30,100
endif
if (B0>10) and (B0<15) THEN
PWM PORTC.1,60,100
endif
IF (B0>15) AND (B0<20) THEN
PWM PORTC.1,100,100
endif
IF (B0>20) AND (B0<25) THEN
PWM PORTC.1,127,100
endif
IF (B0>25) AND (B0<28) THEN
PWM PORTC.1,160,100
endif
IF (B0>28) AND (B0<30) THEN
PWM PORTC.1,200,100
endif
if (B0>30) and (B0<32) then
PWM PORTC.1,254,100
endif

GOTO main

GETRESULT:
PAUSEUS 50 'WAIT FOR ADC SETUP
ADCON0.2 = 1 'START CONVERSION BY SETING GO/DONE BIT HIGH

LOOP: ' WAIT FOR GO/DONE BIT TO CLEAR
IF ADCON0.2 = 1 THEN
GOTO loop
ENdif
goto main


GETMBAT:
ADCON0 =%00000101 'SET A/D Fosc/32, [4MHz], CHANNEL-0 = ON
GOSUB GETRESULT 'START CONVERSION
B0 = ADRES 'STORE THE A/D CONVERSION VALUE IN RESULT
RETURN


The PIC that I am using is PIC 16F874A, and i am trying use a 10k potentiometer to control the motor speed (increase or decrease the speed). Thus, I try the HPWM before, just cant get the result also.

Hopefully, somebody will help me...thanks u