On 23 April 2010 20:29, Dave <[email protected]> wrote: > > Just make sure that you don't get an encoder with > too many Pulses per rev if you are strictly using a LPT port to read the > encoder.
You can (in theory) go pretty fast before running out of speed on the LPT. With a 1000-pulse counter and a 20uS base thread you can do 3000rpm (or call it half that for oversampling) That does suggest that a 256-count would be better. > I purchased an encoder off Ebay (about $60) and then bought a couple of > chips to translate the differential encoder signal into a lpt compatable > signal. (about $20 for the adapter) It works very well. Cheaper still, you can make your own. I ran a laser-printed encoder using reflective sensors for quite a while. They need to be focussed-type (I used Optek OPB 702) and a comparator (eg LM393) in the circuit helps to sharpen up the edges. I got the parts from RSwww.com , I see you are in the UK too, so if you have trouble buying from them I might be able to help. I later machined an aluminium encoder disc, but I kept the same sensors and interface. http://picasaweb.google.com/bodgesoc/Gibbs#5437112859354194098 and following. -- atp ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
