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Relay making PIC stop

 
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Markdem



Joined: 24 Jun 2005
Posts: 206

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Relay making PIC stop
PostPosted: Wed Mar 28, 2007 4:54 pm     Reply with quote
Hi All, i have tried to make a light conntroller that is controled using MIDI commands. It all works very well, but when i connect anything to the relays, eg to the 240VAC side, the PIC will stop about 2 sec later. Nothing happends if i unplug the light. I have tried to use diffrent devices on the 240 side, but it does not help.

The only thing that i can tell is it must be somewhere between when the PIC recived that data, and when i try to decode it, as PIN_E0 will be on when it stops.

The relays are powered off a diffrent power supply, and are connected via a darlington array.

Can anyone see why this may be happening??

Thanks, Mark

Code:

#include <18F4550.h>
#fuses HSPLL,NOWDT,NOPROTECT,NOLVP,NODEBUG,USBDIV,PLL5,CPUDIV1,VREGEN,NOBROWNOUT
#use delay(clock=48000000)

#use rs232(baud=31250, BITS=8, xmit=PIN_C6, rcv=PIN_C7, ERRORS)

#define USB_CON_SENSE_PIN    PIN_D1


#include <STDLIB>
#include <usb_cdc.h>

int1 MIDIDataIN;         
int BeatStep, i, Loutput, Qcount;
int MIDImsg;
int BeatMask[35];



#int_rda
void MIDIBeatIn()
   {
      MIDIDataIN = 1;
      output_low(PIN_E0);                                          
      MIDImsg = getc();
   }

void SettingDownload()
   {
      disable_interrupts(INT_RDA);
      
      printf(usb_cdc_putc,"200\n");

      for(i=0;i<32;i++)                           //get Beat Masks from host
         {
            BeatMask[i] = get_int_usb();
         }

      printf(usb_cdc_putc,"200\n");

      BeatStep = 0;

      enable_interrupts(INT_RDA);
   }


   
void main()
   {
      delay_ms(100);
      
      BeatStep = 0;
      MIDIDataIN = 0;
      QCount = 0;

      for(i=0;i<32;i++)
         {
            BeatMask[i] = 0;
         }

      usb_init_cs();
   
      enable_interrupts(INT_RDA);
      enable_interrupts(GLOBAL);


      while(1)
         {
            usb_task();

            if (usb_cdc_kbhit())
               {
                  switch(get_int_usb())
                     {
                        case 200:   
                           SettingDownload();
                           break;

                        case 201:   
                            for(i=0;i<32>= 24)                              //Has 24 clocks gone, meaning that is is a beat
                           {
                              printf(usb_cdc_putc,"BEAT!!\r\n");            /////Testing
                              QCount = 0;

                              loutput = BeatMask[BeatStep];
                              output_b(Loutput);
                                          
                              if(BeatStep >= 31)                                             
                                 {
                                    BeatStep = 0;
                                 }
                              else
                                 {
                                    BeatStep++;
                                 }
                           }
                     }
                     
                  output_high(PIN_E0);
               }
         }
   }
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Wed Mar 28, 2007 5:08 pm     Reply with quote
Whenever I hear a problem like this, the first thing I think of is the
"back emf" diode.
http://www.ccsinfo.com/forum/viewtopic.php?t=23634&highlight=relay+diode

There's a schematic diagram showing the diode across the relay's coil,
about half-way down this thread:
http://www.winpicprog.co.uk/pic_tutorial_extras.htm

Here's another page that describes the problem. Scroll about half-way
down to the section on "Quenching diodes".
http://www.bcae1.com/relays.htm
Markdem



Joined: 24 Jun 2005
Posts: 206

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PostPosted: Wed Mar 28, 2007 5:41 pm     Reply with quote
Thanks PCM, i forgot to say that i have back emf diodes installed
rwyoung



Joined: 12 Nov 2003
Posts: 563
Location: Lawrence, KS USA

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PostPosted: Thu Mar 29, 2007 7:38 am     Reply with quote
How much current does your relay's coil require for pull-in and also for hold?

How are you driving the coil? Direct from the pin (generally bad idea) or with some kind of buffer?
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SherpaDoug



Joined: 07 Sep 2003
Posts: 1640
Location: Cape Cod Mass USA

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PostPosted: Thu Mar 29, 2007 1:58 pm     Reply with quote
It sounds like the PIC works as long as nothing is connected to the contacts of the relays, but a load on the relay contacts makes the PIC stop. In that case the problem is not on the coil side of the relay. I would look at the proximity of the 240VAC wiring to the PIC, and maybe add some snubber caps to the relay contacts.
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