Any designs for a cheap x-y position sensor?

Be careful with this one. I don't think a mouse gives an accurate measure of how far you have moved. They depend on on screen feedback to know how far to move it, so there is no reason to be accurate.

Rick

Just have reference markers somewhere which will allow frequent calibration to remove all of the above effects.

Rick

I was amazed at the accuracy of the cheap Logitec mouse. I paid $1. for the mouse at surplus outlet. Just turn the software to 'linear' get rid of that auto speed detect. move it around on a sheet of paper while recording the 'clicks' The backlash in the plastic gearing was easily removed and compensated for. amazing to me was the repeatability of going one way and then back the other way, the repeatability was more than good enough. From memory the 'distortion' from x to y was less than 1-2% !! couldn't believe that one. Plus, there was already a C/C++ library program to ask for the position of the mouse - part of Windows environment. so like for only $1 I got this small range x-y position sensor that had ?? accuracy. From memory it was better than a few mils, have to go check my archives for that info. Better not say without checking.

It probably does do a pretty good job, provided the distance between lens and surface is kept constant. Check out the Avago data on the way the chips work, they're quite impressive, especially for the price.

Unfortunately, like most parts based on consumer markets, the product lifetime tends to be brief, if not nasty and brutish.

Best regards, Spehro Pefhany

OK not flux-gate. A Squid? Some atomic thing? (A Rubidium magnetometer is a long list of insturements I'd like to make someday.) (But most likely never will.)

George H.

You are probably better off with a click or random pattern sent on RF and audio/ultrasonics the time delay gives you your position.

Wind speed will be a serious distorting factor though outside.

as

Geometrics makes an RF based magnetometer that measures earth's field out to 12 digits. We had it out in the field near the Bay, open area, and the reading from left to right had steady digits then fluctuating a little bit digits and the LSD's were totally blindly spinning digits. As I watched the pattern, I noticed the spinning pattern changed a bit and told him about it. He pointed to a greyhound bus 2 blocks away. THAT was disturbing the earth's field enough we could see it!

I feel really, really dense, but I still don't understand how the principle works.Something about kicking electrons up in orbit, then they fall back down and you measure the numbers? or the frequency or something. But what gets me is that 12 digits of reading! Has to be frequency to have that many digits.

er as

The physics is the same as is in atomic clocks. (But they are tickling different atomic (magnetic) transitions.) Try googling "optical pumping". I could talk your ear off... but. (There's a nice article in Scientific American by A. Bloom, 1960, but a quick search on the web only turned up references)

When I was building the first optical pumping in a basement, I could see when parked cars moved about on the street out front. (And that was in a DC measurement.)

The magentic fields in our production space have become so bad (60 Hz AC crud and "DC" changes do to elevators or other bits of iron moving about.) that I have to take new units out to my country 'estate' for testing.

George H.

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On a sunny day (Wed, 19 Sep 2012 07:26:22 -0700 (PDT)) it happened Robert Macy wrote in :

Yes it is some core material that has a coil aoround it that is part of an oscillator. Is a special core material I tried several and could not get that sensitivity. I think they beat the oscillor against a second one, and teh diffrence frequencyis used (zero to Feryy Muts) Ih ave some papers on this, but hey how about you google.

I figured you were talking about an optical mouse. I suppose the mechanical mice can be more accurate, linear, etc.

What did you use it for?

Rick

u.

yeh, you can get ultrasonic anemometers

-Lasse

k to

cheap x-y psoition sensor

Yeah, well I meant what were you measuring the position of? What was the application?

Rick

ack to

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I know, just giving you a hard time.

for keeping track of the position of a small reflective probe used in NDE Instrumentation. To keep track of where the data comes from as a function of x-y position over the surface of a piece of aircraft structure. For me, z axis was NOT necessary, because the algorithm inherently shifts vertical for probe's vertical position anywhere from contact to 1/2 inch above !!

So its a smooth surface.

I wondered.

hamilton

.highlandtechnology.com=A0 jlarkin at highlandtechnology dot com

Where to get $1 USB cameras??

It just dawned on me how to do simple SW conversion!