QTI Sensor Differences

SRLM · 2009-01-18 07:19

Hi,

I was working on making a pair of wheel encoders from the QTI sensors, and I noticed something interresting.When I had both hooked up to the BS2 and ran the code, one would give a black value at about 300, while the other would give something at least a 3800, and both would give really big values for the holes in the wheel (empty space). It's always SenseRight that gives the smaller value. I've determined that the hardware must be the same, since I switched the leads and got the same problem. So, what's not right with my code? It's pretty much standard Parallax issue sample code.

' {$STAMP BS2e}
' {$PBASIC 2.5}

LeftLineSnsrPwr PIN 13
LeftLineSnsrIn  PIN 12

RightLineSnsrPwr PIN 11
RightLineSnsrIn  PIN 10

ClrEOR CON 11

SenseLeft  VAR Word
SenseRight VAR Word


  DO
    GOSUB Distance
    DEBUG HOME
    DEBUG "Encoders Test:", CR
    DEBUG DEC senseLeft, CR, DEC SenseRight, CLREOL
    PAUSE 100
 LOOP

Distance:
  HIGH LeftLineSnsrPwr
  HIGH LeftLineSnsrIn
  PAUSE 1
  RCTIME LeftLineSnsrIn, 1, SenseLeft
  LOW LeftLineSnsrPwr
  LOW LeftLineSnsrIn

  PAUSE 1

  HIGH RightLineSnsrPwr
  HIGH RightLineSnsrIn
  PAUSE 1
  RCTIME RightLineSnsrIn, 1, SenseRight
  LOW RightLineSnsrPwr
  LOW RightLineSnsrIn
RETURN

skylight · 2009-01-18 12:30

Strange you have a difference by a factor of 10 and a bit,·perhaps there is a component value difference on your breadboard between each sensor and the BS2?

SRLM · 2009-01-19 22:24

Hmm. No, I've hooked each up as an identical duplicate. I've also added another three sensors that are to sense lines, so now I have a total of five. When I did that and added the additional code, I got a bunch of large, four digit numbers that didn't seem to have any relevance to the real world. However, when I changed the DEC statement to a DEC5, they work perfectly. Something's fishy...

  DO
    GOSUB Encoders
    GOSUB LineSensor
    DEBUG HOME
    DEBUG "Encoders Test:", CR
    DEBUG DEC5 SenseLeftWheel, CR, DEC5 SenseRightWheel, CR
    DEBUG "Line Sensor Test: ", CR
    DEBUG DEC5 SenseRightLine, CR, DEC5 SenseCenterLine, CR, DEC5 SenseLeftLine
    PAUSE 100 
LOOP

Encoders:
  HIGH LeftWheelSnsrPwr
  HIGH LeftWheelSnsrIn
  PAUSE 1
  RCTIME LeftWheelSnsrIn, 1, SenseLeftWheel
  LOW LeftWheelSnsrPwr
  LOW LeftWheelSnsrIn

  PAUSE 10

  HIGH RightWheelSnsrPwr
  HIGH RightWheelSnsrIn
  PAUSE 1
  RCTIME RightWheelSnsrIn, 1, SenseRightWheel
  LOW RightWheelSnsrPwr
  LOW RightWheelSnsrIn


RETURN

LineSensor:
  HIGH LeftLineSnsrPwr
  HIGH LeftLineSnsrIn
  PAUSE 1
  RCTIME LeftLineSnsrIn, 1, SenseLeftLine
  LOW LeftLineSnsrPwr
  LOW LeftLineSnsrIn

  HIGH RightLineSnsrPwr
  HIGH RightLineSnsrIn
  PAUSE 1
  RCTIME RightLineSnsrIn, 1, SenseRightLine
  LOW RightLineSnsrPwr
  LOW RightLineSnsrIn

  HIGH CenterLineSnsrPwr
  HIGH CenterLineSnsrIn
  PAUSE 1
  RCTIME CenterLineSnsrIn, 1, SenseCenterLine
  LOW CenterLineSnsrPwr
  LOW CenterLineSnsrIn
RETURN

Beau Schwabe · 2009-01-20 04:09

SRLM,

Just for kicks, try to define LeftLineSnsrPwr, LeftLineSnsrIn, RightLineSnsrPwr, and RightLineSnsrIn with 'CON' instead of 'PIN' and see if that makes any difference.

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Beau Schwabe

IC Layout Engineer
Parallax, Inc.

QTI Sensor Differences

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