Help need with Ping))) or IR object detection

Comments

• Mike Green Posts: 23,101

  2012-04-25 15:07 edited 2012-04-25 15:07

  On a cursory scan of your program, you've got lots of places (at least 6) where you have loops (like Task0 and Task1) that rapidly output servo control pulses with no PAUSE. The servos will not respond to these rapid pulses and may just vibrate a little without moving. Fix those first by inserting a PAUSE 17 in the loop and see (and report) what happens.
• Scorpio Posts: 6

  2012-04-25 18:33 edited 2012-04-25 18:33

  Ok. Thanks alot..I will insert the pauses and give u an update.
• Scorpio Posts: 6

  2012-04-25 19:09 edited 2012-04-25 19:09

  Ok...I have made as much adjustments as recommended.When the bot detects the object, it will do the scan then decide which path to take. However, the bot sometimes still continues to rotate left to right continuously. I have also realised that when the bot bot moving forward kinda slow although I have it to move at max speed.
  Here is the updated source code.

  ' {$STAMP BS2}                            ' Target device = BASIC Stamp 2
  ' {$PBASIC 2.5}                           ' Language = PBASIC 2.5
  
  ' -----[ I/O Definitions & Constants ]-------------------------------------------------
  Ping            PIN     15              ' PING))) Sensor
  Piezo           PIN     3               ' Piezo Speaker
  
  
  ' -----[ Variables ]------------------------------------------------------------------------
  
  
  pulseCount      VAR   Byte                ' FOR..NEXT loop counter for turning
  qtis            VAR   Nib                 ' QTI black/white states
  LastMove        VAR   Nib                 'Remembers the last move boe bot made
                                            'LastMove: 2-forward, 6-forward and left, 3-forward and right
  
  Turn            VAR     Nib             ' Current Task
  
  pulseLeft VAR Word
  pulseRight VAR Word
  
  
  distance        VAR     Word            ' Current Distance Of Object
  oldDistance     VAR     Word            ' Old Distance Value
  attempt         VAR     Word            ' Keeps count of the number of attempts made
  counter         VAR     Word            ' PING))) Cycle Counter
  
  
  
  ' -----[ Initialization ]-------------------------------------------------------------------
  
  OUTB = 11                              ' Set OUTB bits to 1
  FREQOUT Piezo, 1000, 2000                    ' Battery Tester
  LastMove = 2  'Forward
  distance = 30
  
  
  
  ' -----[ Main Routine ]---------------------------------------------------------------------
  Main:
  DO                                        ' Main DO...LOOP
    ' Get QTI states
    DIRB = 11                            ' P7..P4 -> output
    PAUSE 0                                 ' Delay = 230 us
    DIRB = 00                            ' P7..P4 -> input
    PAUSE 0                                 ' Delay = 230 us
    qtis = INB                              ' Store QTI outputs in INB
  
  
    SELECT qtis
  
    CASE 00
    GOSUB Ping_Out                           ' PING)))-- Scan For objects in pathway
    IF (distance > 30) THEN
      GOSUB Forward               ' If Yes Go Forward
    ELSE
      GOSUB Decide_Turn
    ENDIF
  
  
    ENDSELECT
  
    PULSOUT 13,pulseLeft ' Apply the pulses.
    PULSOUT 12,pulseRight
  
    PAUSE 17
  
  LOOP
  
  ' -----[ Subroutines - Turn_Check ]---------------------------------------------------------
  Ping_Out:                               ' PING)))
  
    LOW Ping                              ' Force PING))) Line Low
    PULSOUT Ping, 5                       ' Activate PING))) Pulse
    PULSIN  Ping, 1, distance             ' Receive Return Pulse
    distance = distance ** 2257           ' Calculate Distance In cm
    RETURN
  
  
  ' -----[ Subroutines - Forward ]---------------------------------------------------------
  Forward:
    pulseLeft = 850
    pulseRight = 663
    PAUSE 17
  RETURN
  
  ' -----[ Subroutines - Rotate_Left ]---------------------------------------------------------
  Rotate_Left:
    pulseLeft = 650
    pulseRight = 650
    PAUSE 17
  RETURN
  
  ' -----[ Subroutines - Rotate_Right ]---------------------------------------------------------
  Rotate_Right:
    pulseLeft = 850
    pulseRight = 850
    PAUSE 17
  RETURN
  
  ' -----[ Subroutines - Backup ]---------------------------------------------------------
  Backup:
      PULSOUT 13, 650              ' Left Servo Backup Pulse Value
      PULSOUT 12, 850             ' Right Servo Backup Pulse Value
      PAUSE 17
  RETURN
  
  Stop_Moving:
    PULSOUT 13, 750
    PULSOUT 12, 750
    PAUSE 17
  RETURN
  
  Decide_Turn:
  
    oldDistance = 30                      ' Current Old Distance Values
    Turn = 0
  
    GOSUB Stop_Moving
  
    FOR pulseCount = 0 TO 10
      LOW Ping
      PULSOUT 13,650      'Turns Boe Bot to the left
      PULSOUT 12,650
      PAUSE 17            ' Refresh Delay
    NEXT
  
    PULSOUT Ping, 5                     ' Activate PING)))
    PULSIN  Ping, 1, distance           ' Receive Distance Value
    distance = distance ** 2257           ' Calculate Distance In cm
    IF distance > oldDistance THEN        ' Is distance > Last Clear Path
      oldDistance = distance              ' Update oldDistance Value
      Turn = 0
    ENDIF
  
    FOR pulseCount = 0 TO 10
      PULSOUT 13,850      'Turns Boe Bot to the right to return to center
      PULSOUT 12,850
      PAUSE 17
    NEXT
  
    FOR pulseCount = 0 TO 10
      LOW Ping
      PULSOUT 13,850      'Turns Boe Bot to the Right
      PULSOUT 12,850
      PAUSE 17            ' Refresh Delay
    NEXT
  
    PULSOUT Ping, 5                     ' Activate PING)))
    PULSIN  Ping, 1, distance           ' Receive Distance Value
    distance = distance ** 2257           ' Calculate Distance In cm
    IF distance > oldDistance THEN        ' Is distance > Last Clear Path
     oldDistance = distance              ' Update oldDistance Value
      Turn = 1
    ENDIF
  
    FOR pulseCount = 0 TO 10
      PULSOUT 13,650      'Turns Boe Bot to the left to return to center
      PULSOUT 12,650
      PAUSE 17
    NEXT
  
    ON Turn GOSUB Task0, Task1
  
    distance = 50
    RETURN
  
  Task0:
  'Furthest distance dectected on the left
    FOR pulseCount = 0 TO 10
      PULSOUT 13,650      'Turns Boe Bot to the left to return to center
      PULSOUT 12,650
      PAUSE 17
    NEXT
    RETURN
  
  Task1:
  'Furthest distance dectected on the left
    FOR pulseCount = 0 TO 10
      PULSOUT 13,850      'Turns Boe Bot to the left to return to center
      PULSOUT 12,850
      PAUSE 17
    NEXT
    RETURN
  
• Mike Green Posts: 23,101

  2012-04-25 21:05 edited 2012-04-25 21:05

  Between the ENDSELECT and the LOOP, you're outputting only a single pulse to each servo. Is that what you really want to do? I can't rewrite your program for you ... it's too complicated. You're going to have to go through it carefully and examine each place where you want to move the servos. You need to produce a servo pulse about every 20ms and produce the pulses long enough for the servos to move the distance you want. 11 pulses about once every 20ms will take somewhere on the order of 1/4 second. Is that what you need? If you don't produce a servo pulse within about 30ms, the servo will turn off until the next pulse comes in. This will produce jerky movement at best. The PING requires up to about 20ms to take a reading. There's really not enough time for the PING to do its thing, make some decisions, and operate the servo all in a simple loop. That's partly why most PING BoeBot programs stop moving briefly when making distance measurements.
  
  You might consider getting a ServoPal which will take over the production of the servo pulses and relieve the tight timing constraints on your program.
• Scorpio Posts: 6

  2012-04-25 22:10 edited 2012-04-25 22:10

  Ok..Thanks for the help.. I'll go through the code carefully and see what is going wrong and use your advice to improve it..If I am unsuccessful, I will have to resort to the QTI's and IR combination. BTW, is there a way where I can avoid IR jamming?. I was thinking about sending a PWM signal from my IR LEDs, but the problem is, I not sure how to get it done.
• Mike Green Posts: 23,101

  2012-04-26 07:06 edited 2012-04-26 07:06

  "avoid IR jamming" ... probably not. The IR signal is already modulated at 38KHz and the IR detectors are tuned roughly to 38KHz and will reject other frequencies. You could try getting IR detectors designed for other frequencies like 36KHz or 40KHz and modifying your program's FREQOUT statement to match. That won't eliminate the interference, but it may reduce it. DigiKey and Mouser carry equivalent IR detectors to the Panasonic PNA4601M that Parallax uses. Vishay makes a whole line of detectors for different frequencies. The pin connections are different though, so you have to pay attention to the diagram on the datasheet for the device you're using.
• Scorpio Posts: 6

  2012-04-26 08:51 edited 2012-04-26 08:51

  I was considering getting IR Dectectors to operate at different frequencies, but I dont have access to any at the moment and my presentation is due tomorrow..lol..Are they any IR detectors in any household electronic devices that operates at different frequencies besides the 38KHz?
  I also have a BPW77NA Phototransistor http://www.vishay.com/docs/81527/bpw77n.pdf. Can this also be used to detect 36Khz or 40Khz IR signals?
• Mike Green Posts: 23,101

  2012-04-26 09:40 edited 2012-04-26 09:40

  Most household remotes use 38KHz. I wouldn't know what the exceptions are. Unfortunately, you can't use a phototransistor for what you want. Modulated IR is used to avoid interference from room lighting, both 60Hz from fluorescents and higher frequencies from compact fluorescents. The Stamp is incapable of filtering this out by itself and it's incapable of detecting modulated IR by itself. Things like the QTI sensor use unmodulated IR and IR phototransistors because the distances are short and the environment (usually under the robot) is partly shielded from ambient light.
• Scorpio Posts: 6

  2012-04-26 10:10 edited 2012-04-26 10:10

  Oh ok..I understand what you are saying..Thanks for the help. I will have to play around some more with the PING code or use the IR code instead.