RE: [CAD_CAM_EDM_DRO] Quadrature for DIY DRO

I have looked into US Digital quadrature encoders to see if it is
possible to support them in the DRO and I wanted to get some feedback
from people who have used them.
I use a lot of their rotary encoder and some of their 360 LPI linear
encoder strips.
They are good encoders and most importantantly they are cheap. The read
heads are probably made by Agilent( HP) so they are really compatible
with a lot of different applications

The output of the encoders is 5V common collector with a weak
pullup. This is good because the DRO circuit already has strong
pullups on the scale inputs. First question, do other brands of
quadrature encoders use a different voltage level or different output
drivers?

Most encoders either use 5v or 12V but it seems like the 5 volt encoders
are more popular today

For the 5V output signal the US Digital encoders use, the existing
PCB could be easily reworked to accept this. It would consist of
depopulating (or not populating to begin with) the buffer chips which
are three 8-pin DIPs. The wires from the connector would then be
soldered on a couple of the through holes of these DIPS. Second
question, is there a standard style of connector for these encoders?
Would the existing 4 pin mini-DIN work? No
A lot cost AMP 5 pin connector MTA connector is commonly used it is
available from Mouser part number 571-6404405 for around .20. If you
need an encoder to experiement with I will ship you free to move this
project along a small motor that has a typical encoder mounted on it
similar to the US digital and are made by Agilent

I don't think I would be able to support simultaneous reading of both
Chinese scales and quadrature encoders. The PIC is very busy while
triple sampling the Chinese scale serial stream and there is a good
probability that a quadrature pulse could be missed. Third question,
would it be sufficient just to have a setup screen that switched all
inputs between Chinese and quadrature mode?

I think most users would want one or the other but not both.

Some of the quadrature encoders have an index pulse. I don't think
this could be supported in the current design since there are no free
pins left on the PIC. Fourth question, is it OK not support this and
operate the encoders only in absolute mode?

The one advantage of the index is if a rotary encoder was attached to a
spindle you could read the RPM but this is feature creep and not that
important relative to the orginal project of a DRO

Lastly, I don't have any quadrature encoders in my home machine shop
and I do not really have a need. Would anyone be willing to loan a
couple to me to develop this feature?
Sure I would

Dan








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