Stuart Stevenson wrote: > Gentlemen, > I have a manual CMM with scales. The display box is very old and almost > functional. I would like to replace it with EMC2. Simple enough except for > the scale feedback. The scale feedback is four sine waves at 0, 90, 180 and > 270. These are, I think, approx 1 volt magnitude. What can I use to get this > into EMC2 in a usable fashion. > Are these sine waves at the basic resolution of the scale, or do you need to interpolate? If the basic optical resolution is OK, then this is quite simple. Use a comparator to compare 0 vs 180 as your A, and 90 vs 270 as your B. Depending on the actual voltages produced, something like an LM193 might be fine. The LM193 needs a pull-up resistor on the output pin. If run from a 5 V supply, then the range of acceptable inputs might be from 0 to 5 V, for instance. You can run it from 12 V if the encoder output is shifted more than 5 V above ground. > The original display has an 'amplifier, check, divide' board. > I don't know the resolution of the sine wave. > I have an sn7404n chip and a couple germanium diodes hooked to a bread > board. I don't see anything out of the chip. I was expecting a pulse that > would allow me to determine the resolution. At this time I have exceeded my > electronics capabilities. > A real 7404 is a TTL chip, and puts a pretty strong loading on whatever is feeding it. A 74HC04 would not load down the signal. > Is there a chip or reasonable board I can use to change the sine waves to > pulse or quadrature? > Possibly, depending on the voltages mentioned above, a US Digital differential to single-ended converter board would work. That is basically a pair of comparators, but designed for input signals in the 0 to +5V range.
Your encoders actually ARE quadrature, they are just analog quadrature, not squared-up digital signals. Jon ------------------------------------------------------------------------------ Nokia and AT&T present the 2010 Calling All Innovators-North America contest Create new apps & games for the Nokia N8 for consumers in U.S. and Canada $10 million total in prizes - $4M cash, 500 devices, nearly $6M in marketing Develop with Nokia Qt SDK, Web Runtime, or Java and Publish to Ovi Store http://p.sf.net/sfu/nokia-dev2dev _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
