encoder
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Could some one please tell me if its possible to use A lined disk of some sort
attached to the robots rubber tires and count revolutions for speed control of
modified hobby servo motors useing reflected lite from led's if so how would I
make A lined disk to attach to A robots rubber drive wheels.
Thanks in advance for any info it will be greatley appreciated.
max
[noparse][[/noparse]Non-text portions of this message have been removed]
attached to the robots rubber tires and count revolutions for speed control of
modified hobby servo motors useing reflected lite from led's if so how would I
make A lined disk to attach to A robots rubber drive wheels.
Thanks in advance for any info it will be greatley appreciated.
max
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
on how you connect the QRD1114 to the Stamp and possibly even a
snippit of code?
Thanks,
Steve
--- In basicstamps@y..., "David Lawrence" <david@r...> wrote:
> Hi:
>
> Adhesive labels printed with radial segments and using a QRD1114
Fairchild
> sensor has worked well on Boe-Bot wheels.
>
> David H Lawrence
>
> Simple Multi-tasking, Co-Processors, Compilers, and microGUI
> mailto:david@r...
> http://www.rhombus-tek.com
>
>
>
Original Message
> From: "max powell" <mpowell@t...>
> To: <basicstamps@y...>
> Sent: Thursday, October 03, 2002 8:31 AM
> Subject: [noparse][[/noparse]basicstamps] encoder
>
>
> > Could some one please tell me if its possible to use A lined disk
of some
> sort attached to the robots rubber tires and count revolutions for
speed
> control of modified hobby servo motors useing reflected lite from
led's if
> so how would I make A lined disk to attach to A robots rubber drive
wheels.
> > Thanks in advance for any info it will be greatley appreciated.
> > max
> >
> >
> > [noparse][[/noparse]Non-text portions of this message have been removed]
> >
> >
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Subject and
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http://docs.yahoo.com/info/terms/
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> >
>
>
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Adhesive labels printed with radial segments and using a QRD1114 Fairchild
sensor has worked well on Boe-Bot wheels.
David H Lawrence
Simple Multi-tasking, Co-Processors, Compilers, and microGUI
mailto:david@r...
http://www.rhombus-tek.com
Original Message
From: "max powell" <mpowell@t...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, October 03, 2002 8:31 AM
Subject: [noparse][[/noparse]basicstamps] encoder
> Could some one please tell me if its possible to use A lined disk of some
sort attached to the robots rubber tires and count revolutions for speed
control of modified hobby servo motors useing reflected lite from led's if
so how would I make A lined disk to attach to A robots rubber drive wheels.
> Thanks in advance for any info it will be greatley appreciated.
> max
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]
>
>
> To UNSUBSCRIBE, just send mail to:
> basicstamps-unsubscribe@yahoogroups.com
> from the same email address that you subscribed. Text in the Subject and
Body of the message will be ignored.
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
>
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out the appropriate sized encoder disk wheel on paper from the file they
have at http://www.portlandrobotics.org website. Then use some spraw on 3M
glue or adhesive on the CD and carefully skick on the paper disk. Then use a
fresh X-acto blade/knife and cut off the excess.
Some smaller wheels can be done in the same manner, but you might have to
cut out the center a lot more to clear oblong wheel extrusions .
Some guys use black or white line trimming tape and carefully place a bunch
in a spoke pattern on wheels. You can also paint on the lines, but it is
hard to keep them straight.
Small wheels could use encoder disks off a broken or unused optical mouse.
Usually you can get two encoder disks and the sensors as well off the old
mouse.
Using Fairchild QRB1114/1113 sensors is fairly easy. I would suggest a 220
ohm resistor on the IR emitter LED (cathode versus anode ends as
appropriate). One side of the LED goes to V+ or Gnd and the other end goes
to the I/O port pin on your MCU. You can have the LED light up on a Low or
High depending on your choice. On the detector side it is a bit more
complicated, you need to use a LM339 comparator (or LM293), you only need
one comparator out of the four (or two) in the chip for each sensor. One
comparator input goes to the wiper on a 5k pot (with the pot's other two
ends going to V+ and gnd respectively). The other comparator input gets fed
the signal from the IR phototransistor in the QRB1114/1113. You also need a
10k ohm resistor for a pullup on the output of the QRB1114 transistor as it
is a open collector device. The collector goes through a 10k resistor to V+
and the transistor's emitter goes to gnd. The output from the comparator
goes to a I/O pin on the Stamp. If your just going to leave the sensor on
all the time, you can forgo having the stamp turn the QRB1114 emitter LED on
or off by typing the end to V+ or Gnd as required.
Now you adjust the pot to set your sensitivity to your encoder disk. If you
like (I like doing it), is to put a 10k pullup on the output from the
comparator and runa led and a 470 or 560 ohm resistor in parallel with the
10k pullup. Then you can power the circuit and spin the wheel slowly and
adjust the pot until you get a good on off pulse indication. If you use real
small low power LED's you can run a 1k resistor in series with it as well.
Since you have two wheels you'll need to setup two of these in a like
manner. Since a LM339 has four comparators you will have two extra to ignore
or use for something else.
If you can't mount the QRB1114's using a screw and nut easily, you can use a
dab of "GOOP" adhesive to hold them in place. I'd suggest taping the sensors
down and ensure the circuit is working OK, and adjusted first. Then gluing
them down. Don't over do the glue you only need a little dab. If you have to
move or remove the sensor after the glue cures, you can use a Xacto knife
blade and litely tap in between the sensor and the chassis part with the
knife blade to pop the sensor loose, then reglue as needed.
gnd---->cathode--anode>
220ohm---->V+ or to I/O port pin on Stamp
phototransistor
gnd---->emitter--collector>---->10k
>V+
|
----+input to comparator
>10k
V+
gnd---->5k pot--->V+
|
wiper
- input to comparator
-->output from comparator
> 10k pullup
> V+
|
LED----560ohm
> V+
|
|
> to Stamp I/O input pin
(if you want to be safe you can run a 1k
resistor
in series to the input to help protect it
from
accidents)
( as a further safety precaution you could use one of
the
gates on ahex invertor or nand gate as a buffer for
the
QRB1114 IR emitter LED as well)
I hope it makes sense.
Original Message
From: max powell [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=hfC0B4LwBgbkrqaDFbUxlRaO9iBZpOIGWOY1qAd5dUQIHsyVjMSv6cIRsXsMu6xsw7YHfjHEHdO8QpI]mpowell@t...[/url
Sent: Thursday, October 03, 2002 10:31 AM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] encoder
Could some one please tell me if its possible to use A lined disk of some
sort attached to the robots rubber tires and count revolutions for speed
control of modified hobby servo motors useing reflected lite from led's if
so how would I make A lined disk to attach to A robots rubber drive wheels.
Thanks in advance for any info it will be greatley appreciated.
max
[noparse][[/noparse]Non-text portions of this message have been removed]
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Original Message
From: "sjoblin001" <steven_joblin@h...>
To: <basicstamps@yahoogroups.com>
Sent: Thursday, October 03, 2002 10:19 AM
Subject: [noparse][[/noparse]basicstamps] Re: encoder
> This seems to be a hot topic! David - can you give some more details
> on how you connect the QRD1114 to the Stamp and possibly even a
> snippit of code?
>
> Thanks,
>
> Steve
Hi Steve:
Earl Bolinger has already provided an excellent detailed write up on the
1114/3. All that I can add is that if you are not using at distinctly
different light levels or disc patterns, then you can skip the comparator.
Using 300/1600 Drive/Pullup resistors, no Comp, and 22 to 36 segments 'on
the inside' of Boe-Bot wheels has always provided rail to rail outputs
for me.
The transitions will not have the snap nor the benefit of hysteresis
obtained from a sensor (sold by Acroname) which has a Schmidt trigger built
in. But the inherent strobing of the 1114 output as in
www.rhombus-tek.com/SMt_Rob.pdf avoids this potential problem without
hardware. There are still some 8 Pin co-processors available for free if you
follow the link to 'Buy' (they also double as a buffered 57k baud Serial
receivers).
The actual code you requested, becomes nothing more than edge detection
where each segment creates alternate states:
L_Ncdr:
IF L_Last = L_Encdr THEN R_Ncdr
L_Last = L_Encdr:L_Count = L_Count+1
R_Ncdr:
etc
Direction cannot be derived from a single channel encoder, but if being
'Driven' in reverse then that data already exists and needs to determine
that the count is decremented rather than incremented.
David
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