Distance and communication between BS2's
Michael @ Afineol
Posts: 33
What would you use to determine the distance between 2 BS2's (Primary and Slave) within·inches,·and have the slave unit transmit this to the primary unit? I need to be able to detect a seperation of at·least 30+ feet.
Comments
At that distance, you're talking about a rangefinder. You could modify a laser rangefinder so it could be read by one of the BS2s. That's probably the only thing that could give you the sort of resolution you're talking about at that range. In any event, you're talking about expensive external equipment.
I agree with Mike here 100 %, if I'm reading your requirements correctly. I hope I've got this math right. You seem to be looking at an accuracy of 2" in 360", so let's look at that (this is just approximate):
2" / 360" = 1" / 180" = .0055"·or 141 microns
The average human hair lies in the range of 17 to 181 microns. That puts the average human hair at 98 microns.
I'm not sure you can get that kind of accuracy with anything short of a laboratory laser, under laboratory conditions. Just to re-emphasize what Mike said, that means BIG $$$.
Are you sure you need that kind of accuracy? What are you actually trying to do that requires that kind of accuracy?
Let me add just one more thing. If either or both of the Stamps are mounted on mobile platforms, you can kiss any kind of accuracy like this goodbye, as well as repeatability.
Regards,
Bruce Bates
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There is no pleasure in having nothing to do;
the fun is in having lots to do, and not doing it!
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We really need more information here... first thing that comes to mind for me is using some sort of·camera or multiple cameras.
Years ago we used·special IR cameras in a gait analysis program for patients with prosthetic legs to study various walking·patterns.
Placing IR reflective markers on the patient at various joint locations allowed us to capture data into·a computer.·
I say "special·IR camera", because·I had never seen anything quite like it.· It had a B/W pixel resolution of 4096x3072 (4:3 aspects ratio)
... on the back of the camera you could connect a standard monitor·and see·RAW video. (<-At reduced resolution for standard NTSC
output)· The "special" bit is that it also had an RS232 jack, where it did it's own processing to provide X,Y coordinates of where it
detected a reflective marker.· The RAW video was impressive also if you placed your hand in front of the lens.·... Semi-Skin penetrating,
old injuries show up as·re-routed veins near the injury site.
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Anyway I'm not sure the name of the camera company, but I could probably find it with some digging.· Without more information
from you though on what your design direction should be, one of these cameras could directly connect to a "Slave BS2" via·RS232.
Once the Slave BS2 received the coordinates (BOTH BS2's (or multiple BS2's) would have IR reflective markers on them), it could then
send the coordinates to the Master BS2('s) through·a simple·RF link.
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Note: It seems as though the Slave/Master terminology might be better suited in this situation if it is reversed.
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········Also·note, that these cameras did not come without a price... If I remember they were somewhere between $2K and $4K
······· That was awhile ago (15-20) years so prices could have come down considerably.
······· To re-itterate what Mike said though... "In any event, you're talking about expensive external equipment."
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······· Here is a link to a similar Gait Analysis Setup that we used ... http://www.mobilab-khk.be/mobilab/infrastructure.html
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Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 2/1/2008 8:07:47 AM GMT