Re: digital protractor for faceting machine

David,

What O M needs is repeatable measurement within a 0° to 90° range. He
needs to be able to set his angle to the nearest tenth of a
degree. A hundredth is down in the noise range for faceting so an
additional digit in the display is useful only as a relative
indicator. IMO repeatability is more important than dead on accuracy
for this application although that's nice too as long as it's
practical and affordable.

O M,

A good place to start is an article written by Jeff Graham at:
http://www.faceters.com/askjeff/answer121.shtml

US Digital ( www.usdigital.com ) manufactures the encoder used on the
only machine currently made with an encoder instead of a pot that I'm
aware of. That's the Omnie. Jeff carries the Omnie and has a good
writeup on his site for it as well.

I'm not clear on whether you want to modify your existing machine's
head or want to build a digital replacement. To go much further here
requires a bit more info from you, but in either case you want the
pot or encoder mounted directly to the shaft being adjusted so that
backlash in the adjusting mechanism becomes a non issue. This is the
most practical approach amongst many.

Hope this gets you started in the right direction,

Travis

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "ol3_m3" <ol3_m3@...> wrote:
>
> What would be required for circuits and power supply. Would the
worm
> drive have a lot of backlash? any suggestions on where to start
> looking for supplies
>
> O M
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "David G. LeVine"
> <dlevine@> wrote:
> >
> >
> > >I am a new member here and am trying to find information of how
to
> > >build a digital protractor for a faceting machine. Had
information
> > >form a site that used a carbon trim pot, but the site has gone
> black.
> > >from a search of this site I also see information on rotary
> encoders.
> >
> > How fine do you want it to be? The easy way is to buy a 360 line
> > encoder and do 4 count quadrature multiplication on the outputs
> which
> > will give you a 15 minute resolution. Of course you could build
a
> > 129,600 line pair unit with 4 count quadrature multiplication on
> the
> > outputs and get 1 second of resolution. It isn't ever cheap!
> >
> > Most find that a worm setup with a cheaper encoder is a good
> > compromise. A 36:1 worm drive is not hard to do, that means that
> > each turn of the worm is 10 degrees on the gear. A 600 line
> encoder
> > gives 1/4 minute (15 seconds) resolution, a 3,600 line encoder
> gives
> > 1/4 second. I would bet that you don't need more than 1 second
> > resolution (about 1" at 100 yards.)
> >
> >
> > David G. LeVine
> > Nashua, NH 03060
> >
> >
> > --
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> 3/3/2007 8:12 AM
> >
>