asking for clarification

[delifadzli]

Here I would to ask for your opinion regarding my code and diagram.
The code is basically PWM controlling speed of dc motor.
compile = no error

[Ttelmah]

Your duty cycles are wrong.
You have Timer2, counting to 250 (249+1). The PWM, updates _four times_ for each count. So the pwm values run from 0 to 1000. 50% duty cycle will be 500, not 120 - _when the value is stored in an int16_. The compiler looks at the value handed to set_pwm_duty, and if it is an int8, automatically multiplies it by 4 for the set_pwm_duty function. So:

set_pwm_duty(medium);

will basically give just under 50% duty, but:

temp_adc=medium;
set_pwm_duty(temp_adc);

Will give just under 12% duty.

Do the following:

Update your constants, as:

#define medium (500L)
#define slow (100L)
#define fast (700L)

This will force the compiler to treat the numbers as 16bity, no matter what the value.

Best Wishes

[delifadzli]

Thanks for explanation. Can you explain a little bit on how to get 50% duty cycle? I assume 125/249= 0.5 isn't true. Sorry for my weakness.

Then how about cel 20 and cel 50 ...?

Isn't need to replace it? like cel 20 = 250L and cel 50= 600L ??

[Ttelmah]

The PWM, counts to the value you set for timer2 _plus one_, in '1/4' counts. So with Timer2=249, the PWM accepts values from 0 to 1000. With '1000' being 'fully on' (no pulse, signal fully high), and '0' being 'fully off' (signal fully low). The half way point, is 1000/2 = 500. Pulse on 1/4 time, is 250, etc..

Best Wishes

[Ttelmah]

Your 'cel' values, are the value you are reading from the ADC, nothing to do with the PWM values.
The values you need here, will; depend on what you are doing with the ADC.
You don't need to use the 'L' designation for these, since nothing you are doing makes any 'distinction' between 8bit integers, and long (16bit) integers.
The point is that the PWM code _does_ make a distinction. If it receives a 'long' integer (a value >255, a value stored in an int16, _or_ a value with 'L' appended), then it uses this value directly. If it receives an 8bit value, then it automatically multiplies it by 4, assuming that you only want to set the top 8 bits of the 10bit PWM value. This is documented in the manual.

Best Wishes

[delifadzli]

Here is a little improvement that I had managed to compile it without any error...

[delifadzli]

the component 2sj48 i replace it with IRF9540...sorry for that one...

[delifadzli]

anyone?...please help..me...i quite new is this area...actually.....sorry for my weakness

[ckielstra]

Hint: fix the layout of your code. Now the indentation goes left and right at random.

When you have fixed this, look at where the while-loop ends. Do you think this is correct?

[delifadzli]

#include <16F877A.h>
#device ADC=10
#fuses HS,NOWDT,NOPROTECT,PUT,BROWNOUT,NOLVP
#use Delay(clock=20000000)

#include "C:\Users\deli\Desktop\pwx2\brum\Flexlcd2.c"


#define medium 125L
#define slow 63L
#define fast 240L

void main()
{
int16 temp_adc;
float temp;
int16 pwm_duty;




setup_adc(ADC_CLOCK_DIV_8);
setup_adc_ports(PIN_A1);
set_adc_channel(1); //read analog input from channel 1
output_low(PIN_C2); // Set CCP1 output low
setup_ccp1(CCP_PWM); // Configure CCP1 as a PWM
setup_timer_2(T2_DIV_BY_4, 249, 1); // 5khz
set_pwm1_duty(medium); // Set for 50% duty cycle

lcd_init();

lcd_putc("\ftemperature is:\n");

while(1)

{
temp_adc = read_adc();

temp = 5.00*temp_adc*100.00/1023.00;
lcd_gotoxy(1,2);
printf(lcd_putc,"%f",temp);
delay_ms(3000);



if ( temp_adc < 58)
{
temp_adc=slow;
}


if ( ( temp_adc > 58) & ( temp_adc < 70) )
{
temp_adc=medium;
}


if ( temp_adc > 70)
{
temp_adc=fast;
}

set_pwm1_duty(temp_adc); //Change duty cycle and adjust


}

like this?


i truly sorry if i'm wrong...i'm still newbie....

[ckielstra]

Use the 'code' buttons when posting code. Now it is very difficult to read.

[delifadzli]

[ckielstra]