ssir detector, please help

Comments

• Jonb Posts: 146

  2005-04-02 23:16 edited 2005-04-02 23:16

  What components are you using. Are they the standard ones that come with the boe bot? They output high when nothing is detected and low when they detect IR light at the proper frequency. The program you posted seems ok. Only problem I see straight off the bat is that IN0 should be output when sending out the 38.5khz signal then set to input to check for result.
  
  I recently set up a pair of IR emitters and detectors following directions in the boe bot documentation page 245.
  
  http://www.parallax.com/dl/docs/books/edu/Roboticsv2_2.pdf
  
  Also I tested the sensors by placing a LED on the output pin which greatly helped in troubleshooting. If your IR emitter/detector is a 1 pin component, then changing input/output direction will work.
  
  Post Edited (Jonb) : 4/2/2005 11:46:52 PM GMT
• Chris Savage Parallax Engineering Posts: 14,406

  2005-04-03 01:44 edited 2005-04-03 01:44

  Mike,
  
  ·· I see one more problem in your code...Don't know which part is wrong, but DIR0 = 1 sets it to an OUTPUT not an INPUT as the comment describes.
  
  
  
  ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
  Chris Savage
  Parallax Tech Support
  csavage@parallax.com
• allanlane5 Posts: 3,815

  2005-04-03 20:07 edited 2005-04-03 20:07

  I think I would do:
  
  '{$stamp BS2}
  '{$PBASIC 2.5}
  
  ' Pin 0 FREQOUT sends an IR signal.
  ' Pin 0 input reads the IR-Detector.
  
  INPUT 0 'sets pin 0 - to imput
  
  Holdbit VAR Bit 'sets up a variabe for the echo
  
  start:
  FREQOUT 0,1,38500 'sends out 1 mSec signal to IR LED -- and leaves pin an output
  INPUT 0
  Holdbit = IN0 'store reply
  
  DEBUG 1,"sensor =", DEC Holdbit,CR ' dispays resutlts
  GOTO start
  
  ' Note HoldBit == 1 on no-reflection, 0 on reflection
• 111mike Posts: 2

  2005-04-04 23:39 edited 2005-04-04 23:39

  Thanks Allan,
  
  Your suggestions worked. I was even able to write a quick program to get our motors to respond once an object is detected. This has helped out immensely. Here is the whole thing program if you're interested. Pretty small potatoes. If you have a moment, I was wondering why it is 0 on reflection and not a 1. I think I'm missing something here.
  
  Thanks again for your help,
  
  111mike
  
  
  '{$stamp BS2}
  '{$PBASIC 2.5}
  
  
  speed VAR Byte
  Holdbit VAR Bit 'sets up a variabe for the echo
  x VAR Byte
  
  
  
  
  
  DO
  
  GOSUB pathchecker
  GOSUB forward
  
  
  LOOP
  
  ' -- -- subroutines -- --
  
  
  Pathchecker:
  
  
  ' Pin 0 FREQOUT sends an IR signal.
  ' Pin 0 input reads the IR-Detector.
  
  INPUT 1 'sets PIn 1 - To input
  
  
  
  
  start:
  
  FOR x=1TO 100
  
  PAUSE 50
  FREQOUT 1,1,38500 'sends out 1 mSec signal to IR LED -- and leaves pin an output
  INPUT 1
  Holdbit = IN1 'store reply
  
  DEBUG 1,"sensor =", DEC Holdbit,CR ' dispays resutlts
  IF holdbit = 0 THEN forward
  NEXT
  
  
  END
  
  ' Note HoldBit == 1 on no-reflection, 0 on reflection
  
  
  
  
  Forward:
  
  
  HIGH 6 'take serial line high
  
  LOW 8 ' reset motor controller
  
  HIGH 8
  
  PAUSE 100 ' motor controller start up time
  
  
  FOR speed = 0 TO 50
  
  SEROUT 6, 84, [noparse][[/noparse]$80, 0, 1, speed] 'third number in brackets is motor control,
  SEROUT 6, 84, [noparse][[/noparse]$80, 0, 3, speed] 'L.motor=0, R.motor=1, FWD=1,RVS=0, motor control value(3rd #)is
  'motor#(0 or 1)times 2, + value for FWD. or Rvs.(0 or 1).
  'see note, page 8, motor control handbook
  
  
  PAUSE 20
  
  NEXT
  PAUSE 5000
  
  FOR speed = 50 TO 0
  
  SEROUT 6, 84, [noparse][[/noparse]$80, 0, 1, speed] 'stops
  SEROUT 6, 84, [noparse][[/noparse]$80, 0, 3, speed]
  
  
  
  PAUSE 20
  NEXT
  PAUSE 1000
  
  GOTO pathchecker
• allanlane5 Posts: 3,815

  2005-04-05 14:19 edited 2005-04-05 14:19

  Why 1 on no-detect? Well, the reason is because the IR-Detector is an 'active' device. There's really quite a lot going on inside that little square of plastic. It's looking for a particular blink-rate frequency of blinking IR light. When it doesn't see one, it lets its output 'float' up to 5 volts. When it does see one, it provides a 'low' signal on its output.
  
  That's how the device works. I know it seems counter-intuitive, but that's what the designers did. I'm sure they had a good reason for doing it that way (less power required? Better signal detect? Wired-Or configuration?) but that's the short answer.