temperature controlled fan

[Amith Jose]

hey am a newbie , trying to make a temp controlled fan using a pic16f877a.
i hope to vary the rpm using PWM .
i made a design and code but unfortunately smething's wrong with it..

i have like zero experience when it comes to PWM, so i doubt the problem is with my code.
I used an 'lm35' to sense the temp and a 'l293d' as the driver circuit to run the fan ..

please help me out .

//code



#include <16F877A.h>
#device adc=8

#FUSES NOWDT,HS
#use delay(clock=20000000)
#include <lcd.c>

void main()
{
int x;

lcd_init();
setup_adc(ADC_CLOCK_DIV_32);
setup_adc_ports(ALL_ANALOG);
setup_timer_2(T2_DIV_BY_4,255,1);
setup_ccp1(CCP_PWM);
delay_ms(500);
while(1)
{
set_adc_channel(0);
x=read_adc();
delay_ms(5);

lcd_putc('\f');
lcd_gotoxy(1,1);
lcd_putc("Temp");

printf(lcd_putc,"%u\n",2*x);
delay_ms(20);



if(x<40)
{ set_pwm1_duty(3*x);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_C7);

}
else if(x>40)
{set_pwm1_duty(255);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_c7);
}
else
{OUTPUT_LOW(PIN_C6);
OUTPUT_LOW(PIN_C7);
set_pwm1_duty(0);
}
}
}

 

[Jinzpaul4u]

Hello there,

i made a design and code but unfortunately smething's wrong with it..

what is the problem are you facing???

Best regards,

 

[kam1787]

why is set_adc_channel in the loop?

 

[Amith Jose]

the problem i am facing is that the fan rotates at times, sometimes it rotates for a while and then slows down and stops,
temp detecting part is ok, but cant control the fan speed..

 

[Jinzpaul4u]

Hello there,

f(x<40)
{ set_pwm1_duty(3*x);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_C7);

}
else if(x>40)
{set_pwm1_duty(255);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_c7);
}
else
{OUTPUT_LOW(PIN_C6);
OUTPUT_LOW(PIN_C7);
set_pwm1_duty(0);
}
}
}

x=read_adc();

Can you check whether X is constant value or not?? it might be the problem from adc read .. ADC values may varying and it enters the if -else loop randomly ..Check your hardware connection and analog voltage strength?? is there any noisy signal on analog input pin??

Update me.

Best regards,

- - - Updated - - -

Try these too

[B]set_adc_channel(0);[/B]
while(1)
{

x=read_adc();
delay_ms(5);

lcd_putc('\f');
lcd_gotoxy(1,1);
lcd_putc("Temp");

printf(lcd_putc,"%u\n",2*x);
delay_ms(20);



if(x<40)
{ set_pwm1_duty(3*x);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_C7);

}
else if(x>40)
{set_pwm1_duty(255);
OUTPUT_HIGH(PIN_C6);
OUTPUT_LOW(PIN_c7);
}
else
{OUTPUT_LOW(PIN_C6);
OUTPUT_LOW(PIN_C7);
set_pwm1_duty(0);
}
}