Optimizing IR range

[dhouston]

Anand,

I found a page from someone who reverse engineered a Canon remote.

• http://www.doc-diy.net/photo/rc-1_hacked/

[ardhuru]

Dave, thanks for the link. I had stumbled upon that site, and used the information there to be the basis for my own design. The guy uses an Atmel, which was another incentive for designing my own around a pic. But of course, the detail timings table he's given helped a lot.

In the page you pointed out, the writer uses a switch to control the Vdd itself; when I tried that my signal burst was not very clean. So my version has Vdd always connected to the battery and 2 separate momentary contact switches for the 2 functions.

My version is now working very well, functionally, so am now in the process of reducing the current consumption. Shutting off the watchdog, configuring the I/Os and using a nap in the loop has now reduced it to around 40 uA; I guess that means a single CR2032 should last for well over half a year of average use!

Again, thank you so much for the inputs.

Regards,

Anand

[ardhuru]

Shutting off the watchdog,

Sorry, my mistake, that has to be kept on.

[ardhuru]

Okay folks, with all the help from you guys, I have this working pretty well now.

For the benefit of others designing an IR transmitter powered from a typical coin battery, I would like to share this point. Once you have the basic thing working, probably the one single factor to increase the range significantly would be a large capacitor (100uf plus) across the battery.

I dont know how this would impact the battery life though.

Regards,

Anand

[peu]

Dave, thanks for the link. I had stumbled upon that site, and used the information there to be the basis for my own design. The guy uses an Atmel, which was another incentive for designing my own around a pic. But of course, the detail timings table he's given helped a lot.

Anand, can you post the part of the code where you encode the trigger for the Canon, I would like to add it to the timelapse remote I'm building. Thanks!!

Pablo

[ardhuru]

Hi Pablo,

Thats a nice idea; a sort of semi-universal (Pentax/Nikon/Canon) time lapse trigger.

The Canon trigger is perhaps the simplest to encode. I'm pasting my code, of which you could delete the delayed-trigger related lines. These a re used on the remote to trigger the shutter 2 seconds after the signal is sent.

    Main:
    NAP 0                           ; Reduce consumption in standby from 900uA to 116uA (cost of 18ms delay)
    IF SW1 = 0 THEN GOSUB NO_DLAY
    IF SW2 = 0 THEN GOSUB DLAY
    GOTO MAIN
 
    NO_DLAY:
    HIGH LED
    CYCLES = 16                     ; COUNTER HAS TO BE RESET TO DEFAULT!
    Gosub Pulse
    PAUSEUS 7300
    CYCLES = 16                     ; COUNTER HAS TO BE RESET TO DEFAULT!
    GOSUB PULSE
    PAUSE 50                       ; Prevent inadvertant double triggerPAUSE 500
    LOW LED
    PAUSE 500
    RETURN
  
    DLAY:
    HIGH LED
    CYCLES = 16                     ; COUNTER HAS TO BE RESET TO DEFAULT!
    Gosub Pulse
    PAUSEUS 5300
    CYCLES = 16                     ; COUNTER HAS TO BE RESET TO DEFAULT!
    GOSUB PULSE
    PAUSE 50                       ; Prevent inadvertant double triggerPAUSE 500
    LOW LED
    PAUSE 500
    RETURN
    
    Pulse:          ' THIS GENERATES "Cycles" number of 40kHz pulses (if total delays are 25)
                    ' So, for Canon, 16 Cycles of 31 uS (32.6 KHz) => Demodulated pulse of 0.496 mS
ASM
   bsf IRTX,PIN     ; 1uS, LED=on
   goto $+1         ; + 2uS = 3uS
   goto $+1         ; + 2uS = 5uS
   goto $+1         ; + 2uS = 7uS
   goto $+1         ; + 2uS = 9uS
   goto $+1         ; + 2uS = 11uS
   goto $+1         ; + 2uS = 13uS   
   goto $+1         ; + 2uS = 15uS 
   goto $+1         ; + 2uS = 17uS 
   bcf IRTX,PIN     ; 1uS, LED=off
   goto $+1         ; + 2uS = 3uS
   goto $+1         ; + 2uS = 5uS
   goto $+1         ; + 2uS = 7uS
   goto $+1         ; + 2uS = 9uS
   goto $+1         ; + 2uS = 11uS
   decfsz _Cycles,f ; + 1uS = 12S           ; This decrements in a loop till 0; then goes to next line    
   goto _Pulse      ; + 2uS = 14uS
   return           ; Return to caller    
ENDASM
  
    END

Would be nice to have your feedback on the finished product.

BTW, in your schematic you have a pullup on the switch input; cant you just enable the internal pullup?

Regards,

Anand