That Rocks! Terrific job. Do you have a video of it in action? Also, can the ticks be finer, or rather thinner and closer together to get it more accurate?
Get Control of your Wiper Motor
I finally figured out how to use a Parallax QTI Line Sensor, HB25 Motor Controller, and a BS2 to sense and control the shaft position of a wiper motor.
I made a 3" disk with "tic" marks in PaintshopPro, glued it to a cardboard disk, drilled out the center, mounted it over the shaft, then hot glued the QTI to a standoff, and hot glued that to the motor over the "tic disk".
http://www.spooksterville.com/gallery3/albums/batch/normal_P4010032.JPG
The QTI outputs a pulse each time it sees a transition from black to white. The BS2 reads the pulses and sends positioning commands to the HB25. The shaft can be positioned anywhere you want it... near a tic mark
http://www.parallax.com/detail.asp?product_id=555-27401
http://www.parallax.com/detail.asp?product_id=29144
Whats it good for? turning heads, lifting arms/legs/torsos, pulling a prop a precise distance...and back
Here's sample code that will position the shaft a 1/2 rotation CW, back to start position, then CW 1 full rotation and back to starting position...with a few pauses.
' {$STAMP BS2}
' {$PBASIC 2.5}
'
' =========================================================================
' -----[ Program Description ]---------------------------------------------
' This code utilizes a QTI as an encoder
' -----[ I/O Definitions ]-------------------------------------------------
' qti w goes to Vdd
' qti r Output Connects To P0
HB25 PIN 15
trigger PIN 14
' -----[ Constants ]-------------------------------------------------------
T2400 CON 396
T9600 CON 84
T38K4 CON 6
Inverted CON $4000
Open CON $8000
Baud CON Open | T38K4 ' fast baud for accessories
IsOn CON 1 ' for active-high I/O
IsOff CON 0
' -----[ Variables ]-------------------------------------------------------
oldBits VAR Nib ' Previous State Of I/O Pin 0
newBits VAR Nib ' Current State Of I/O Pin 0
counter VAR Byte ' Counter (0-255)
index VAR Word
' -----[ Initialization ]--------------------------------------------------
OUTS = %1000000000000000 ' Set All Output Pins Low but 15
DIRS = %1111111111111110 ' I/O Pin 0 is Input
newBits = INA
' -----[ Program Code ]----------------------------------------------------
main:
'DO WHILE trigger= IsOff: LOOP 'take out the ' to use a trigger
counter =0
DO : LOOP UNTIL HB25 = 1 ' Wait For HB-25 Power Up
LOW HB25 ' Make I/O Pin Output/Low
PAUSE 5 ' Wait For HB-25 To Initialize
PULSOUT HB25, 750
PAUSE 5000
CW:
PULSOUT HB25, 780 'start motor
CCW:
PULSOUT HB25, 710
Halt:
PULSOUT HB25, 750
encoder:
DO WHILE counter < 62
newBits = INA ' Get State Of I/O Pin 0
IF newBits <> oldBits THEN ' Have Bits Changed?
counter = (counter + 1) 'Start counter
IF counter = 10 THEN CCW
IF counter = 20 THEN CW
IF counter = 40 THEN ccw
IF counter = 61 THEN Halt
DEBUG HOME, ? counter ' Show New Counter On Screen
oldBits = newBits ' Update oldBits
ENDIF
LOOP
RETURN
I made a 3" disk with "tic" marks in PaintshopPro, glued it to a cardboard disk, drilled out the center, mounted it over the shaft, then hot glued the QTI to a standoff, and hot glued that to the motor over the "tic disk".
http://www.spooksterville.com/gallery3/albums/batch/normal_P4010032.JPG
The QTI outputs a pulse each time it sees a transition from black to white. The BS2 reads the pulses and sends positioning commands to the HB25. The shaft can be positioned anywhere you want it... near a tic mark
http://www.parallax.com/detail.asp?product_id=555-27401
http://www.parallax.com/detail.asp?product_id=29144
Whats it good for? turning heads, lifting arms/legs/torsos, pulling a prop a precise distance...and back
Here's sample code that will position the shaft a 1/2 rotation CW, back to start position, then CW 1 full rotation and back to starting position...with a few pauses.
' {$STAMP BS2}
' {$PBASIC 2.5}
'
' =========================================================================
' -----[ Program Description ]---------------------------------------------
' This code utilizes a QTI as an encoder
' -----[ I/O Definitions ]-------------------------------------------------
' qti w goes to Vdd
' qti r Output Connects To P0
HB25 PIN 15
trigger PIN 14
' -----[ Constants ]-------------------------------------------------------
T2400 CON 396
T9600 CON 84
T38K4 CON 6
Inverted CON $4000
Open CON $8000
Baud CON Open | T38K4 ' fast baud for accessories
IsOn CON 1 ' for active-high I/O
IsOff CON 0
' -----[ Variables ]-------------------------------------------------------
oldBits VAR Nib ' Previous State Of I/O Pin 0
newBits VAR Nib ' Current State Of I/O Pin 0
counter VAR Byte ' Counter (0-255)
index VAR Word
' -----[ Initialization ]--------------------------------------------------
OUTS = %1000000000000000 ' Set All Output Pins Low but 15
DIRS = %1111111111111110 ' I/O Pin 0 is Input
newBits = INA
' -----[ Program Code ]----------------------------------------------------
main:
'DO WHILE trigger= IsOff: LOOP 'take out the ' to use a trigger
counter =0
DO : LOOP UNTIL HB25 = 1 ' Wait For HB-25 Power Up
LOW HB25 ' Make I/O Pin Output/Low
PAUSE 5 ' Wait For HB-25 To Initialize
PULSOUT HB25, 750
PAUSE 5000
CW:
PULSOUT HB25, 780 'start motor
CCW:
PULSOUT HB25, 710
Halt:
PULSOUT HB25, 750
encoder:
DO WHILE counter < 62
newBits = INA ' Get State Of I/O Pin 0
IF newBits <> oldBits THEN ' Have Bits Changed?
counter = (counter + 1) 'Start counter
IF counter = 10 THEN CCW
IF counter = 20 THEN CW
IF counter = 40 THEN ccw
IF counter = 61 THEN Halt
DEBUG HOME, ? counter ' Show New Counter On Screen
oldBits = newBits ' Update oldBits
ENDIF
LOOP
RETURN
1 - 8 of 8 Posts
Thanks...no, i dont have the means to do video right now...i wish.
Im not sure on the gaps for more accuracy. I suppose so, at low rpm. At higher rpm the tics become a blur. I have to do some more experimenting to see what the limitations are but Im excited as to the possibilies. My reason for pursuing this was to raise/lower a heavy porp arm and let out/take in a specific length of line on a reel.
edit: The sensor counts at the begining and end of a tic so there is actually more resolution than just one tic/one count. Said another way, you can stop the motor at the start of a tic or the end of a tic...i hope im making sense...
Im not sure on the gaps for more accuracy. I suppose so, at low rpm. At higher rpm the tics become a blur. I have to do some more experimenting to see what the limitations are but Im excited as to the possibilies. My reason for pursuing this was to raise/lower a heavy porp arm and let out/take in a specific length of line on a reel.
edit: The sensor counts at the begining and end of a tic so there is actually more resolution than just one tic/one count. Said another way, you can stop the motor at the start of a tic or the end of a tic...i hope im making sense...
Wow. Very nice work randyaz! Great information. Thanks for sharing.
That's one heck of a strong servo you've built there bro. Nice job!
Oh, yea, that makes sense. That's alot better it senses the beginning and end of the ticks..that doubles the "resolution". Have you thought about hacking a mouse sensor? Not an optical one, a ball one. Just wondering your thoughts on it.Thanks...no, i dont have the means to do video right now...i wish.
Im not sure on the gaps for more accuracy. I suppose so, at low rpm. At higher rpm the tics become a blur. I have to do some more experimenting to see what the limitations are but Im excited as to the possibilies. My reason for pursuing this was to raise/lower a heavy porp arm and let out/take in a specific length of line on a reel.
edit: The sensor counts at the begining and end of a tic so there is actually more resolution than just one tic/one count. Said another way, you can stop the motor at the start of a tic or the end of a tic...i hope im making sense...
Randy,
You might consider the use of LOOKDOWN and ON GOSUB to streamline your code; the way it's written right now you can have one routine fall into another and I don't think that's what you want, even if the HB-25 tends to ignore pulses that fall into the "ignore" time frame.
You might consider the use of LOOKDOWN and ON GOSUB to streamline your code; the way it's written right now you can have one routine fall into another and I don't think that's what you want, even if the HB-25 tends to ignore pulses that fall into the "ignore" time frame.
... just a follow up: SELECT-CASE would work very nicely, too. One of the advantages of PBASIC 2.5 is all the niceties added that come from the PC programming world.
1 - 8 of 8 Posts
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