Alternate method to determine position in two axis besides using linear encoders?

[metalman8357]

Hello,

I'm working on a project where I will need to determine and record the XY position of a stylus over an 18" x 36" table. The stylus will be mounted on a gantry to move freely in the Y axis, and will also be mounted on a slide on the gantry beam to move freely in the X axis. I want the user to be able to hand move the stylus and have the program record it's XY coordinates every 1/10th of a second.

I've looked into using linear encoders for this but the cost is far too expensive. Is there any other cheap and simple method that I can use that can (somewhat) accurately determine the XY position of the stylus without using linear encoders? I've thought about using a stepper motor and counting steps but the resistance will be to great to move the stylus easily.

Any ideas would be greatly appreciated!
Thanks,
-M

 

[PNachtwey]

I don't understand. We make small linear motion demo units. We use quadrature encoders that cost about $75. I don't know if they have a z pulse. For a small system like you describe you can just run the stylus into to end stop and set the position.

Peter Nachtwey
Delta Computer Systems

http://www.deltamotion.com

http://forum.deltamotion.com/

 

[itsmoked]

Use really small stepper motors and gear them so they don't affect the motion.

Or.

Use touch circuits with linear tapers to allow reading the positions of the two axis. Use a micro with a charge peripheral like most Microchip processors to pole the "touch" point. Tiz very fast and cheap.

Alternatively use variable inductance coils where the axises run a core into coils changing their inductance. Measure the position by measuring the inductance.

Or use a Kinect and just look at the hand.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[blacksea]

And what's about mouse including internal image processing with XY pixels outputs?

 

[mcgyvr]

define cheap?
define accurately?

String pots?
Ultrasonic?

https://www.sparkfun.com/products/13959