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'[OT] Sensor to count slates?'
1998\04\18@085455 by aama–o

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In a project that I am carrying out should I count a I number uncertain of
heaped slates some above other, do I ignore the sensor type that could use,
I have tried to use laser, but is the refraction index very variable, could
ultra-sounds be used maybe? some idea?


Investimento e Investigacion Industrial, S.L.
P.O.BOX 103
32300 Barco de Valdeorras (Orense)
Spain
TLF.   : (+34)909 256412
FAX    : (+34)988 300044
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1998\04\20@102008 by Tom Handley

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  Manuel, that's sounds like a tough one. Maybe we could help if you could
give us a little more information.

1. What kind of material are the slates made out of?
2. Are the slates the same size and thickness?
3. Are the slates always stacked at the same level (ie: 1, 2, etc, slates)?
4. Is there any edge of the slates that does not overlap another slate?

  - Tom

At 02:47 PM 4/18/98 +0200, Manuel wrote:
{Quote hidden}

1998\04\20@173904 by XYGAX

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In a message dated 20/04/98  14:20:57, you write:

<<    Manuel, that's sounds like a tough one. Maybe we could help if you could
give us a little more information.

1. What kind of material are the slates made out of? >>

SLATE [sleit] 1 nu 'bluish-grey rock which breaks easily into thin sheets . 2
nc thin piece of this rock used for covering the roofs of houses, or for
writing on. Also vt say that someone / something is very bad. The critics
slated his latest play..........'

Well thats wot dictonary says could it be that a large pile of critics has
been found and we wish to count them in order to assign them numbers ?

Sorry Steve..........

1998\04\25@083746 by aama–o

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Fecha: lunes 20 de abril de 1998 16:22
Asunto: Re: [OT] Sensor to count slates?


>   Manuel, that's sounds like a tough one. Maybe we could help if you could
>give us a little more information.
>
>1. What kind of material are the slates made out of?


Yeah! Slates are "thin piece of this rock used for covering the roofs of
houses".

>2. Are the slates the same size and thickness?


yes, they are approximately same size and thickness.

>3. Are the slates always stacked at the same level (ie: 1, 2, etc, slates)?


The number of heaped slates is variable.

>4. Is there any edge of the slates that does not overlap another slate?


Alone it is accessible a lateral of each slate.


>   - Tom

Thank you for the demonstrated interest!.

>
>At 02:47 PM 4/18/98 +0200, Manuel wrote:
>>In a project that I am carrying out should I count a I number uncertain of
>>heaped slates some above other, do I ignore the sensor type that could
use,
>>I have tried to use laser, but is the refraction index very variable,
could
>>ultra-sounds be used maybe? some idea?


Investimento e Investigacion Industrial, S.L.
P.O.BOX 103
32300 Barco de Valdeorras (Orense)
Spain
TLF.   : (+34)909 256412
FAX    : (+34)988 300044
E-MAIL: manuel.castrospamKILLspammx3.redestb.es
>>
>>

1998\04\26@155405 by Tom Handley

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  Manuel, I'm affraid I can't be of much help. As far as slates, in my
`neck of the woods' they can be made of different kinds of rocks or other
material. Unless you can get a clear path for an optical beam that can be
interrupted for each slate I would look at measuring the weight. Since they
are about the same size and the same material, you might weigh them where
they are collected (ie: a bin). Frankly, I would look at the cost of having
your customer changing the method of moving the slates in a way that would
allow for standard optical counting.

  - Tom

At 11:42 PM 4/24/98 +0200, you wrote:
{Quote hidden}

1998\04\27@080153 by Simon Melhuish

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I wonder how different is the reflectivity of front and side surfaces?
Perhaps using polarized light...

I seem to recall that when I've pointed my camera at a house with a slate
roof a polarizing filter made quite a difference. It might have been wet
at the time.

To expose some of the front surface of each, they could perhaps be stacked
in a "hopper" that is not quite square, and leans backwards. As the
dimension of each slate is not fixed, you'd have to look at the rear
portion against the back, with a slot cut in the back of the hopper. Aim a
light source at the "staircase" of slate edges, at an angle, and measure
the reflected light with a light sensor behind a polarizing filter.

The above is totally untested. Apologies if it duplicates anything
already said.

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

Dr. Simon J. Melhuish
N.R.A.L., Jodrell Bank.
http://www.jb.man.ac.uk/~sjm/

1998\04\27@095055 by Bill Cornutt

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This sounds like something out of the Flint Stones.  In fact this slate slab counter may well be used in a quarry.  Which implies dust and vibration.  Anything to do with lights may have problems with the dust over everything.  And even the light source/sensor may get cloged with dust.

Also, if my memory serves me right (which it does less and less these days) slate is composed of layers of rock.  And a slab can be split into two slabs easly.  What that means is that the edges will have horzional lines across it where the different layers have ben deposited a few years ago.  And this could look like where one slab meets another slab.

If a measurment of the height of the rock pile would susfice, then it may be possible to hand a rod down in the path of the pile.  As the pile goes under the rod, it pushes rod foward.  As the rod is pivioted above, this just tilts the rod from the vertical.  When the pile gets far enuff along the line that it starts to pass under the rod and the rod starts to drag along the top, the rod will stop changing its angle of dangle for a peroid of time.  This steady angle can be a signal that the rod is at the top of the pile.  Then it is a little bit of math or something to determin the hight of the pile.

One problem may occcure if a real small pile goes through with a real high pile in front and behind it.  And visaversa.

Bill C.  EraseMEbillspam_OUTspamTakeThisOuTcornutt.com



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{Quote hidden}

1998\04\27@173518 by Chris Eddy

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How about using an air tube on the conveyor that has a pressure switch attached
(or transducer with PIC!) which senses the presense of the slate when the air
pressure raises in the tubing.  Just a few pointers, use a flow or needle
regulator on the line coming from the compressor, so that the pressure can build
up on the exit end when blocked.  Also, use a solid pipe for the vertical portio
n
on the conveyor, tapping in the flexible air hose say half way down.  That way,
when garbage falls into the pipe, it can build up in the pipe some ways before
causing trouble.  You could then empty the pipe from time to time.  With the air
flow, I don't predict that too much junk will get in anyhow.

Depending on your ratio of off pressure to on pressure (related to the
effectiveness of the slate blockage and air flow) you could have a reliable
sensor, or then again you could have a dog.

Chris Eddy
Pioneer Microsystems, Inc.

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1998\04\28@181652 by aama–o

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Hello again to the group, I believe that the best solution is the proposal
for Chris Eddy, I will try to use a sensor of pressure to detect the
variations of pressure taken place by the presence of the slate.

I have tried to use laser-diodes but it was not possible to carry out the
reflection of the ray on the slate.



Investimento e Investigacion Industrial, S.L.
P.O.BOX 103
32300 Barco de Valdeorras (Orense)
Spain
TLF.   : (+34)909 256412
FAX    : (+34)988 300044
E-MAIL: manuel.castrospamspam_OUTmx3.redestb.es

1998\04\29@005250 by ape

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Manuel Castro Caama–o wrote:

> Hello again to the group, I believe that the best solution is the proposal
> for Chris Eddy, I will try to use a sensor of pressure to detect the
> variations of pressure taken place by the presence of the slate.
>
> I have tried to use laser-diodes but it was not possible to carry out the
> reflection of the ray on the slate.

Why don't you just place a sheet of metal (or some other reliable reflective
material) on
TOP of the stack of slates, measure, and subtract 1 due to the thickness of
the metal.

I have worked with load cells (used with electronic weight measurement) and it
is highly
variable if not made correct.  Linearity and temperature drift are two big
issues.  Of
course you could always buy a counting scale.  You going to load the slates on
the scale
by hand?  Or are you going to load them on a pallet and load the pallet on the
scale?  If
you use different pallets, the weight difference between pallets will throw
off results.

How accurate do you want this?  20%?, 5%?, .00001%?

1998\04\29@153852 by Tom Handley

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  Manuel, I also think Chris has a good idea. My concern is maintenance
and the relative slow response of pressure sensors. Can you describe the
conveyor system in more detail? How fast do the slates travel? As far as
optical methods, if you can get a `clear shot' at the individual slates,
a simple modulated IR system will work even in the presence of dust that
(I imagine) you would encounter. You need to use a separate transmitter
and receiver, not a reflected beam. You certainly don't need a LASER
for this. I use to design these kinds of things for saw mills. One
application measured raw-cut lumber of various sizes on a conveyor.

  - Tom

At 09:30 AM 4/28/98 +0200, you wrote:
{Quote hidden}

1998\04\30@083818 by aama–o

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The solution proposed by Mark Devin is not viable, since the weight of each
slate unit is very variable depending on the quality of the slate.

At the moment they are considering four possibilities:

1 - to use a jet of air and a valve that it detects the presence of the
slates detecting the variations of pressure.

2 - to use an originator of infrareds and to detect the variation in the
intensity of the ray reflected when moving it along the whole pile of
slates.

3 - to use light Laser detecting the variation in the intensity of the ray
reflected when moving it along the whole pile of slates.

4 - to use ultra-sounds, although this system seems the but difficult.

The main difficulty is due to that the slates are very tight among if, and
it becomes very difficult to detect the valleys that exist contiguous slates
between two. Cases also exist in that the depth of the holes that there are
slates between two is of 1 millimeter.


Investimento e Investigacion Industrial, S.L.
P.O.BOX 103
32300 Barco de Valdeorras (Orense)
Spain
TLF.   : (+34)909 256412
FAX    : (+34)988 300044
E-MAIL: KILLspammanuel.castroKILLspamspammx3.redestb.es


'[OT] Sensor to count slates?'
1998\05\01@032812 by wft
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Please describe the problem and environment again.

Gus
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1998\05\04@063440 by aama–o

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The slates are piled vertically in wood pallets forming several layes, 2 or
more rows in each layer depending on the slate size. Slates have many sizes
and forms. They can be from 2 to 5 millimeters thick.
The slate edges have a 45 deegres slope which helps rain to flow away when
put in roofs.
When piled in pallets, they are kept tight by using a rubber hammer. So we
get a variable gap between two slates depending on the slate edge slope and
the slate irregularities.
At present, when one layer is done, the worker counts manually how many
slates are in the rows of a layer, before another layer is put.
One of the problems to solve would be to count the slates placed in the
begining and end of the row as there can be wood very close (may be an
algorinth must take care of this and sum 2 to the resulting count).
I also suppose the reading should be done twice, one in each direction, and
give an audible signal if both readings are the same.



Investimento e Investigacion Industrial, S.L.
P.O.BOX 103
32300 Barco de Valdeorras (Orense)
Spain
TLF.   : (+34)909 256412
FAX    : (+34)988 300044
E-MAIL: manuel.castroEraseMEspam.....mx3.redestb.es

1998\05\04@085556 by Bill Cornutt

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> The slates are piled vertically in wood pallets forming several layes, 2 or
> more rows in each layer depending on the slate size. Slates have many sizes
> and forms. They can be from 2 to 5 millimeters thick.
> The slate edges have a 45 deegres slope which helps rain to flow away when
> put in roofs.

It becomes obvious that you require a hand held device.

Does the slate reflect or absorb infrared?  If it absorbed,
would a infrared source heat the slate enuff so that a
detector could detect it?  Would there be enuff ambient
infrared emitted from the slate so that no source was
needed?  Would the sun be a good source and the resultant
reading be of  shade'  no shade'?

If infrared is used and if a source is also used, I have some
advice.  There is a infrared detector that detects a modulated
infrared signal.  Also pulsing the source will help in keeping
the ambient infrared from confusing things.  I have not tried it
but I think that you should take a  floor' reading with the
source off, pulse the source on and take another reading.
The difference between the two is the useful information.

If dust is a problem you may need to use the  kiss a duck'
method.  When you kiss a duck it is necessary to first blow
a little puff of air to move the feathers out of the way.

You idea of taking two readings sounds great.  Maybe
they should be taken in two directions.  The first from top
to bottom, and the second from bottom to top.

Sounds like a fun project and one especially suited for
a Pic in a hand held device..

Bill C.   EraseMEbillspamcornutt.com

1998\05\04@094120 by Bill Cornutt

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This is the second reply to your post today.

After thinking about it, the answer came.

When I was a kid we would clip a playing card or baseball card
to our bycicle so that as the wheel turned the spokes in the
wheel would hit the card,  This would make a noise as we rode
the bycicles so that we 'played like' our bikes were a
motorcycle.

Take a piece of stiff plastic. attatch it to the end of a stick.
Place a microphone on the end of the stick near the plastic.
Then as you run the stick up and/or down the pile, it will make
a noise as it passes over the edges.  The signal from the
microphone can then be analized by the hand held device (held
in the other hand?) attached to the stick/microphone.

Bill C.   bill@cornutt

1998\05\04@095906 by Andy Kunz

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>Does the slate reflect or absorb infrared?  If it absorbed,

Go work on a slate roof and find out :-0

Andy

==================================================================
Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
==================================================================

1998\05\04@122342 by Bill Cornutt

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> >Does the slate reflect or absorb infrared?  If it absorbed,
>
> Go work on a slate roof and find out :-0
>
> Andy
>
> ==================================================================
> Andy Kunz - Statistical Research, Inc. - Westfield, New Jersey USA
> ==================================================================
>

I deserved that.

Bill C.

1998\05\04@135244 by David VanHorn

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> >Does the slate reflect or absorb infrared?  If it absorbed,
>
> Go work on a slate roof and find out :-0
>
> Andy


I deserved that.

Bill C.


Actually, there's a huge difference between near IR at about 900nM and heat
IR (longwave) at about 10,000nM

You can also use specular and diffuse reflections to distinguish a target.
I've done this for reflectively sensing paper behind lexan, where the lexan
may be dirty/scratched. The sensor is designed to optimise diffuse
reflections and reject specular. (Cost: $1.50)

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