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Using a LED as Light sensor

 
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Jody



Joined: 08 Sep 2006
Posts: 182

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Using a LED as Light sensor
PostPosted: Wed Oct 28, 2009 4:23 am     Reply with quote
Hello,

I am trying to use a LED behave as a LIGHT sensor.
Like this example. So reverse the LED and measure the voltage.
http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html

When I do that (no PIC attached) I wil see a light related voltage across the LED.
But when I attach the PIC(12F615) I get a stable 200mV.

Did I did something wrong with the PIC settings????
Code:

unsigned int   red_duty, light;

void main()
{
   setup_adc_ports(sAN3|VSS_VDD);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DIV_BY_16,255,1);
   setup_ccp1(CCP_PWM);
   
   while(1){

   set_adc_channel(3);
   delay_us(10);
   light = read_adc();
   light = light * 1;
   set_pwm1_duty(light);
   }
}


Thanks in advance,

Jody
Jody



Joined: 08 Sep 2006
Posts: 182

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Got it working!
PostPosted: Wed Oct 28, 2009 8:49 am     Reply with quote
The Vref setting messed things up.............

Code:

void main()
{
   setup_adc_ports(sAN3|VSS_Vref);
   setup_adc(ADC_CLOCK_INTERNAL);
   setup_timer_0(RTCC_INTERNAL|RTCC_DIV_1);
   setup_timer_1(T1_DISABLED);
   setup_timer_2(T2_DIV_BY_16,255,1);
   setup_comparator(NC_NC_NC_NC);
   setup_ccp1(CCP_PWM);
   set_pwm1_duty(512);;   

   while(1){
   delay_ms(255);
   delay_ms(255);
   light_old = 0;
   light = 0;
   set_adc_channel(3);
   delay_us(10);

      for(i = 0; i <1000; ++i)
      {
      light = read_adc();
      light_old = light_old+light;
      }
      light = (light_old / 1000);
      if(light < 15) light =15;
      set_pwm1_duty(light);;     
   }
}
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