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[DPRG] Re: The quadrature blues, or- The Tale of two sensors

Subject: [DPRG] Re: The quadrature blues, or- The Tale of two sensors
From: David Peterson robologist at yahoo.com
Date: Tue Aug 28 15:25:26 CDT 2001

You know, this kind of makes sense in transmissive wheels.
Kind of how you can see light around a corner, even though
the source is blocked, and the detector could be getting
almost enough to be getting to it's on threshold. It might
also have some effect in reflective encoders, as the white
part maybe getting enough reflected light to start the
detector turn on earlier than a standard 50/50 square wave.
Don't now how feasible this is in making a homebrew encoder,
but it's an interesting thought.
David P

----- Original Message -----
>From: "R. Bickle" <rbickle at swbell.net>
To: "'Kipton Moravec'" <kip at kdream.com>; "'David P.
Anderson'" <dpa at io.isem.smu.edu>; <dprglist at dprg.org>
Sent: Tuesday, August 28, 2001 2:05 PM
Subject: RE: [DPRG] Re: The quadrature blues, or- The Tale
of two sensors


> Kip,
>
> Yes, this information is a rule of thumb for transmissive
type encoders. I
> should have mentioned that. This is I believe is related
to the relationship
> between on times / off times for the phototransistors.
When the encoders are
> made with this ratio, the results (with transmissive
optointerrupters) yield
> a good 50% duty waveform. It may not be the case with
reflective types.
>
> Rick
>
>
> -----Original Message-----
> From: dprglist-admin at dprg.org
[mailto:dprglist-admin at dprg.org]On Behalf
> Of Kipton Moravec
> Sent: Tuesday, August 28, 2001 1:49 PM
> To: R. Bickle; 'David P. Anderson'; dprglist at dprg.org
> Subject: Re: [DPRG] Re: The quadrature blues, or- The Tale
of two
> sensors
>
>
> I have been monitoring the communications.  You stated
> >
> > Also, you should keep the opens to closes at a 2/3
ratio. If you want the
> > period of the encoder to be say 0.050", then make the
open .020" and the
> > close 0.030".
> >
>
> I don't understand why.  Every program that generates a
reflective pattern
> is evenly spaced black and white.  That is what David
Anderson is using.
>
> Or are you saying that the little encoder wheels that have
slits for light
> to pass through, has this ratio?  I never looked close
enough to notice.
>
> Kip
>
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