> > I came across these sensors a few years ago while working on a
> > project to automatically sort cattle through automatic gates. These
> > proved excellent for sensing black cows (very low infrared
> > reflectivity)... for example other opto sensors we trialled would
> > give a number of output pulses as a Friesian/Holstein cow (black and
> > white patches) walked past!
> >
> > http://sunxsensors.com/index.php?main_page=3Dindex&cPath=3D40_146
> >
> > They have several noteworthy characteristics as far as Infrared
> > diffuse reflective photoelectric sensors go: 1) Not affected by
> > object colour or background 2) Adjustable distance (ignores objects
> > beyond set distance), mechanical adjuster not electrical 3) Large
> > operating range (at least 2m)
> >
> > I would like to know how they work, instruction manual gives some
> > clues. From page 2 of manual, "Principle of fixed-focus sensing with
> > 2-segment photodiode" "Normal reflective type sensors operate by
> > sensing the variation in the amount of incident beam. However, the
> > fixed-focus reflective sensing type sensor incorporating the
> > 2-segment photodiode operates by sensing the variation in the
> > incident beam angle. Thus, the output is activated according to the
> > distance of the object from the sensor. This system helps the EQ-30
> > series in being unaffected by object color or a background, enabling
> > stable sensing."
> >
> > I can perhaps visualise how 2 sensors help differentiate between
> > near and far objects. A lens (or even a pinhole?) might allow the
> > incident beam angle to hit one or both sensors depending on distance
> > to object... I could be wrong and/or there might be more to it than
> > that. How would that help with object colour performance?
>
> The SUNX terminology is a bit confusing, usually "fixed-focus"
> (sometimes called "background blanking") is a cheap form of "true"
> Background Suppression using light triangulation. Usually they use
> only one photodiode and the sensing range is usually only good around
> the focus range. Probably the SUNX sensor is the true BGS type and use
> light triangulation. It will belong to the type of
>
> Mechanical  background suppression" is usually more expensive and
> better than "electronic background suppression".
>
> Ref:
> http://www.sensorsmag.com/sensors-mag/the-rise-diffuse-mode-photoelect
> ric-sensors-1506 http://www.pepperl-fuchs.com/global/en/15514.htm
> http://www.baumerelectric.com/usa/news/Minos/MINOS_BGS_essay.html
>
> > I'm researching sensors for another application, which requires 1
> > and 2 above but not necessarily 3 (0.5m range would be ok). The SunX
> > sensor would do it, but way too expensive (USD148).
> >
>
> You may want to check if they have visible red light version which
> will have lower sensing distance. SUNX sensors are usually cheaper
> than companies like SICK, Omron and Pepperl+Fuchs but it all depends
> on the source you get. You might want to search the offerings from
> these vendors and other vendors (in US, there is Banner Engineering).
>
> This one is the latest from Pepperl+Fuchs and I do not know the price.
> http://www.pepperl-fuchs.com/global/en/15171.htm
>
> I was the lead designer (project lead, HW and FW designer) for the
> Series 31 (RL31/RLK31) photoelectric sensor released back in 2006 when
> I was working for Pepperl+Fuchs Singapore, but the above one is a
> later addition to the series.
>
> --
> Xiaofan
>=20

Many thanks! Good info in those links, just the explanation I needed for ho=
w=20
Background Suppression works.

Yes, I think the SUNX sensor is "true" Background Suppression from observin=
g the=20
way it behaves... it has a very precise cut-off point (adjustable operating=
 distance)=20
that does not seem to vary with objects of different reflectivity. Perhaps =
it technically=20
does have fixed focus optics, and the mechanical adjuster shifts the positi=
on of the=20
photodiodes? I'll ask about a visible red version, though they don't list o=
ne on their=20
website. =20

Now I'm also wondering about Foreground Suppression, but at least I now kno=
w a=20
bit more terminology which will help in my searching. =20

I imagine it would have been very interesting to work on the RL31/RLK31
sensor project, and rewarding to see your "babies" graduate into the real w=
orld :-)
--=20
Brent Brown, Electronic Design Solutions
16 English Street, St Andrews,
Hamilton 3200, New Zealand
Ph: +64 7 849 0069
Fax: +64 7 849 0071
Cell: +64 27 433 4069
eMail:  brent.brown@clear.net.nz



--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.