IR Sensors

ltmhall · 2007-01-22 17:30

I'm having a problem getting my IR emitter/led pair to run the fastIRroaming program on
a robot i'm building using the basic stamp II and wanted to know what other IR sensors
are out there I can use for· collision avoidance.

Steve Joblin · 2007-01-22 17:37

Sharp makes a variety of IR Sensors, but could you elaborate as to what type of problem you are having?

Phil Pilgrim (PhiPi) · 2007-01-22 17:48

Make sure that the sensor receives no light directly from the IRED. This will almost certainly involve shielding the IRED with either black shrink tubing or putting it in an LED holder with a snap-on bezel. Then put the business end of the IRED forward of the sensor. This is necessary because IREDs leak light out the rear, and sensors do not completely block light coming in from the rear (unless they have a metal shield arount them, as some do).

-Phil

ltmhall · 2007-01-22 19:22

When both pair sense an object it seems to reverse in a jerking fashion. When I place my hand right in front of both senors it backs up okay. However when I place my hand in front of both sensors from further away my robot starts jerking. The right and left sensor seem to work okay independently from each other. Initially I tried RoamingWithIr.bs2 and it worked perfect.

allanlane5 · 2007-01-22 19:47

If RoamingWithIR.bs2 worked perfectly, then it's definitely not a hardware problem.

Would you like to post your code as an attachment?

Steve Joblin · 2007-01-22 19:53

Looks like this is already being addressed in http://forums.parallax.com/showthread.php?p=626241...

No double postings please!

ltmhall · 2007-01-22 19:55

This is my code

Robotics with the Boe-Bot - FastIrRoaming.bs2
' Higher performance IR object detection assisted navigation
' {$STAMP BS2}
' {$PBASIC 2.5}
DEBUG "Program Running!"
irDetectLeft VAR Bit ' Variable Declarations
irDetectRight VAR Bit
pulseLeft VAR Word
pulseRight VAR Word
FREQOUT 4, 2000, 3000 ' Signal program start/reset.
DO ' Main Routine
FREQOUT 3, 1, 38500 ' Check IR Detectors
irDetectLeft = IN2
FREQOUT 1, 1, 38500
irDetectRight = IN0
' Decide how to navigate.
IF (irDetectLeft = 0) AND (irDetectRight = 0) THEN
HIGH 4
HIGH 5
pulseLeft = 650
pulseRight = 850
ELSEIF (irDetectLeft = 0) THEN
HIGH 5
pulseLeft = 850
pulseRight = 850
ELSEIF (irDetectRight = 0) THEN
HIGH 4
pulseLeft = 650
pulseRight = 650
ELSE
LOW 4
LOW 5
pulseLeft = 850
pulseRight = 650
ENDIF
PULSOUT 15,pulseLeft ' Apply the pulse.
PULSOUT 14,pulseRight
PAUSE 15
LOOP

allanlane5 · 2007-01-22 20:21

I think the reason your robot is jerking is you are only allowing a SINGLE move per measurement. Your robot doesn't move very much in 20 mSec.

Thus, when detecting things at the edge of sensor detection, it backs a little, doesn't see it, moves forward a little, sees it, backs up a little, doesn't see it, etc. All at a 20 mSec delay, which is about 50 times a second. I'm not surprised it 'vibrates'.

Solution: Put your "PULSOUT" statements in a short loop -- do it 25 times. That will be 1/2 second of movement for each sense, which should allow some movement before the next sense statement.

ltmhall · 2007-01-22 23:19

I tried creating a small loop for the PULSOUT but it still reacts the same way.

* Program with PULSOUT loop

DEBUG "Program Running!"
irDetectLeft VAR Bit ' Variable Declarations
irDetectRight VAR Bit
pulseLeft VAR Word
pulseRight VAR Word

DO
GOSUB IR_TEST
GOSUB PULSOUT_MOVE
LOOP

IR_TEST:
FREQOUT 3, 1, 38500 ' Check IR Detectors
irDetectLeft = IN2
FREQOUT 1, 1, 38500
irDetectRight = IN0
' Decide how to navigate.
IF (irDetectLeft = 0) AND (irDetectRight = 0) THEN
HIGH 4
HIGH 5
pulseLeft = 650
pulseRight = 850
ELSEIF (irDetectLeft = 0) THEN
HIGH 5
pulseLeft = 850
pulseRight = 850
ELSEIF (irDetectRight = 0) THEN
HIGH 4
pulseLeft = 650
pulseRight = 650
ELSE
LOW 4
LOW 5
pulseLeft = 850
pulseRight = 650
ENDIF
RETURN
PULSOUT_MOVE:
PULSOUT 15,pulseLeft ' Apply the pulse.
PULSOUT 14,pulseRight
PAUSE 15
RETURN

allanlane5 · 2007-01-23 14:01

That's not a loop, that's a subroutine CALL.

To loop it, you'd do:

FOR I = 1 to 25
GOSUB Pulsout_Move
NEXT

This way, you'd move for 500 mSec, before you tried sensing again. It's that Sense-move-sense-move repetition 50 times a second that's getting you.

ltmhall · 2007-01-23 14:06

So it would just be

DEBUG "Program Running!"
irDetectLeft VAR Bit ' Variable Declarations
irDetectRight VAR Bit
pulseLeft VAR Word
pulseRight VAR Word

DO
GOSUB IR_TEST
FOR I = 1 to 25
GOSUB Pulsout_Move
NEXT

LOOP

IR_TEST:
FREQOUT 3, 1, 38500 ' Check IR Detectors
irDetectLeft = IN2
FREQOUT 1, 1, 38500
irDetectRight = IN0
' Decide how to navigate.
IF (irDetectLeft = 0) AND (irDetectRight = 0) THEN
HIGH 4
HIGH 5
pulseLeft = 650
pulseRight = 850
ELSEIF (irDetectLeft = 0) THEN
HIGH 5
pulseLeft = 850
pulseRight = 850
ELSEIF (irDetectRight = 0) THEN
HIGH 4
pulseLeft = 650
pulseRight = 650
ELSE
LOW 4
LOW 5
pulseLeft = 850
pulseRight = 650
ENDIF
RETURN
PULSOUT_MOVE:
PULSOUT 15,pulseLeft ' Apply the pulse.
PULSOUT 14,pulseRight
PAUSE 15
RETURN

allanlane5 · 2007-01-23 14:13

Yup, that should do it.

ltmhall · 2007-01-23 14:15

Right now i'm at work and when I get home I'll give it a try and let you know if it works.

THANKS

Post Edited (ltmhall) : 1/23/2007 2:19:21 PM GMT

allanlane5 · 2007-01-24 02:15

Yeah, you probably need a

I VAR BYTE

declaration in there somewhere.

IR Sensors

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