hbg6@citek.mcdphx.mot.com (02/14/91)
Does anyone out there know of an INEXPENSIVE sensor for determining the position of a shaft? A standard shaft encoder would be nice but they run about $85 which is a bit steep for this home project. I'd also like to avoid potentiometer / AtoD systems because there such a pain to build. Any ideas? Thanks, John ..................................................................... reply to 'from' address; hbg6@citek.mcdphx.mot.com NOT the 'sender' line address! Someday my sysadm will decide this is a 'real' problem. :-) ..................................................................... All opinions expressed are mine and not Motorolas, their loss. .....................................................................
faunt@dustbin.cisco.com (Doug Faunt N6TQS 415-688-8269) (02/15/91)
Couple a pot to the shaft, and measure the resistance.
larry@kitty.UUCP (Larry Lippman) (02/16/91)
In article <14570@mcdphx.phx.mcd.mot.com> hbg6@citek.mcdphx.mot.com writes: >Does anyone out there know of an INEXPENSIVE sensor for determining >the position of a shaft? >A standard shaft encoder would be nice but they run about $85 which is a >bit steep for this home project. If you have a microprocessor-based system which can count pulses, then an optical incremental encoder is pretty inexpensive. If you need absolute angular position with binary or BCD output, then an $ 85.00 encoder sounds like a pretty good deal to me! An incremental encoder can be made with a toothed wheel that interrupts an LED/phototransistor pair. For finer resolution, you will need an optical disk with ruled lines. Such a disk can be made by plotting the radial ruling lines, making a transparency thereof, and carefully gluing the transparency to a clear plastic disk which fits over the shaft. Using two LED/phototransistor pairs positioned over inner and outer rulings with the same number lines, but which have a suitable angular offset will give you a quadrature output that can be used to sense direction (i.e., cw or ccw). >I'd also like to avoid potentiometer / AtoD systems because there such >a pain to build. A resolver with a packaged resolver->digital converter is a better method for an analog approach. You may be able to find something in a surplus store. Larry Lippman @ Recognition Research Corp. "Have you hugged your cat today?" VOICE: 716/688-1231 {boulder, rutgers, watmath}!ub!kitty!larry FAX: 716/741-9635 [note: ub=acsu.buffalo.edu] uunet!/ \aerion!larry