# Sensors to detect and measure movement

I would like to know which sensors should I use in order to get measurement of a movement of my device (slow speed movement on a 2D plane, in cm or mm if possible). The goal is to find out if the user has moved the device from a starting point and to calculate the distance between the two points.

EDIT:

The plane will be 2.0m x 0.5m. It will be a device held by a person that will begin the "measurement" at the intersection of the diagonals of the plane. The user can lift the device. I can't tell you exact the speed right now - just a slow hand movement (but the speed will not be constant).

I would appreciate any advice on a device that could rotate; But in this case I am asking for a non-rotating device (there will be single point to track). There are no cost restrictions, the smaller the device, the better.

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How large is the plane- length x width? Can the user lift the device? What speed max? Can the device rotate? How large a volume (w x h x d) is available for the movable part if needed. Acceptable cost? Environment? Actual description of what you REALLY want to do would help muchly. Ring/hand/robot/battleship. mm/m/km. ... –  Russell McMahon Mar 11 '12 at 22:34
The plane will be 2x0,5 m. It will be a device hold by a person that will begin "measurement" at the intersection of the diagonals of the plane. The user can lift device. I can't tell you exact the speed right now - just a slow hand moves. I would appreciate any advice on the device that would rotate as feel but in this case I am asking for a non-rotating device (there will be single point to track). There are no cost restrictions, the smaller the device would be, the better. –  REACH Mar 11 '12 at 22:44
Question is not clear, a diagram would be great. I can recommend an optical method for tracking that uses a few components and can be accurate to the mm but we need to know things like, you need average speed or just left arrived or speed profile during the motion etc. etc. –  Ktc Mar 13 '12 at 13:37
The smallest device to handle this (that i have seen) the Advanced RF Remote based on CC2533 SoC (ti.com/lit/ug/swru266a/swru266a.pdf) This is a remote but designeing a PCB as Small as 2cmx2cm is possible with 0603 discrete components using zigbee wireless. But measuring distance might need gps? or some other clever stuff –  ppumkin May 11 '12 at 11:33
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## 1 Answer

How much cpu do you already have available (if any)?

Try Googling for "optical flow" - the hardware in optical mouses uses very low resolution cameras (8x8 or 16x16 pixels) and create sub millimeter resolution xy data from them. There's a bunch of optical flow stuff in OpenCV (which is exposed in the Processing OpenCV library), but I haven't used the optical flow functions myself. You'd then have the problem of getting the camera data off the object into a machine running the OpenCV code. Another option would be have a camera above the device/surface and use object tracking (which I'd also jump towards OpenCV for first).

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"Try Googling" is not considered to be a good answer here. You Google and tell us here what you found. –  stevenvh May 11 '12 at 6:19
@stevenvh: IMHO the suggestion of using the optical flow and a camera is not really a plain "use google" answer but much more helpful. –  0x6d64 Jun 10 '12 at 15:31
@ox6d64 - When a comment starts with "IMHO" it often means I'm wrong :-). But this time I don't think I am. Googling for "optical flow" return 869000 hits. Now what??? I'd rather have 1 single useful link than having to dig my way through those thousands to find that really interesting one. bigiain probably got his information from an interesting site. Then why not post that link here? –  stevenvh Jun 10 '12 at 15:37
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