Optical Positioning
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Posts: 46,084
I am looking to monitor the position of two items in relation to each
other. The items will be about 8 inches apart and will move in a
linear motion (parallel to each other) about 2 inches. There will be
no way to mechanically connect the two items so they have to be
monitored optically and the sensing needs to be fairly accurate (down
to about 1/4 inch).
What I was thinking of doing was mounting a laser diode on one of the
items and then sensors on the other. I could then monitor which
sensor the laser beam fell on to find the position.
I guess the first question is does this sound like a sensible way to
do this?
Next, I found the 67-1500-ND laser diode which looks like it will
work for my purposes and is fairly inexpensive. What would be a good
sensor to go along with this?
other. The items will be about 8 inches apart and will move in a
linear motion (parallel to each other) about 2 inches. There will be
no way to mechanically connect the two items so they have to be
monitored optically and the sensing needs to be fairly accurate (down
to about 1/4 inch).
What I was thinking of doing was mounting a laser diode on one of the
items and then sensors on the other. I could then monitor which
sensor the laser beam fell on to find the position.
I guess the first question is does this sound like a sensible way to
do this?
Next, I found the 67-1500-ND laser diode which looks like it will
work for my purposes and is fairly inexpensive. What would be a good
sensor to go along with this?
Comments
scan cameras, along with read-out circuitry. Hitachi makes them among
other mfrs. They should be spectrally matched to the laser diode for
best resolution and performance.
Dennis
Original Message
From: rcvehicles [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=0rGRKcX1lE4VOSc6fT0Hkkoun-HE0bkjOm5vW7acBPMh9UDWd-KlG9gyrAgjOI30Ngbnq_oZNFsnPgaMxg]hankster@h...[/url
Sent: Tuesday, September 03, 2002 2:54 PM
To: basicstamps@yahoogroups.com
Subject: [noparse][[/noparse]basicstamps] Optical Positioning
I am looking to monitor the position of two items in relation to each
other. The items will be about 8 inches apart and will move in a
linear motion (parallel to each other) about 2 inches. There will be
no way to mechanically connect the two items so they have to be
monitored optically and the sensing needs to be fairly accurate (down
to about 1/4 inch).
What I was thinking of doing was mounting a laser diode on one of the
items and then sensors on the other. I could then monitor which
sensor the laser beam fell on to find the position.
I guess the first question is does this sound like a sensible way to
do this?
Next, I found the 67-1500-ND laser diode which looks like it will
work for my purposes and is fairly inexpensive. What would be a good
sensor to go along with this?
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Original Message
> From: rcvehicles [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=r_Mh_W0bbP-sSdbVp6_7xJUSNCLMLFcaRCSFS1JpO8W4A-jyPiM4Yx4rbwx_nPX-EP22ULVTMXW9LD8]hankster@h...[/url
> Sent: Tuesday, September 03, 2002 4:54 PM
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] Optical Positioning
>
> I am looking to monitor the position of two items in
> relation to each
> other. The items will be about 8 inches apart and will
> move in a
> linear motion (parallel to each other) about 2 inches.
> There will be
> no way to mechanically connect the two items so they have
> to be
> monitored optically and the sensing needs to be fairly
> accurate (down
> to about 1/4 inch).
>
> What I was thinking of doing was mounting a laser diode on
> one of the
> items and then sensors on the other. I could then monitor
> which
> sensor the laser beam fell on to find the position.
>
> I guess the first question is does this sound like a
> sensible way to
> do this?
>
This is one of those "off the top of you head" ideas. I saw a movie
called "The Dam Busters", based on WWII history. In the movie special
bombs were dropped at night, onto the water, from a specific low
altitude. The pilots were having problems holding the correct altitude,
until one of them had an idea while watching a show at the theater. The
spotlights gave him an idea. They fixed a small spotlight to the bottom
of the plane, near the nose, and another near the tail. They were aimed
in such a way as to converge on the water's surface when the plane was
the correct height. A spotter in the belly of the plane, feeding back
to the pilot how they were doing, too high or too low. In your
application two IR emitters could be directed at one detector. When the
range was correct the detector would be receiving the strongest signal.
I have used detectors with a base lead, allowing you to reduced the
gain, so you could tune it to be in the linear part of the detector's
range. At least it would seem to be a possible solution to me.
Digikey numbers L14G2 detector and F5D1 emitter will work up so about
8"-10"(with nothing special being added) with a beam that can be
interrupted by a single strand of phone wire, so being set at about 45
deg, I would expect a good response range when the separation was
changing inside your 1/4" range.
Dan Thames
> Next, I found the 67-1500-ND laser diode which looks like
> it will
> work for my purposes and is fairly inexpensive. What would
> be a good
> sensor to go along with this?
>
>
> 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/
>