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From: Glen Walpert on 16 Apr 2010 19:19
On Sat, 17 Apr 2010 08:05:20 +1000, Tony wrote:

> On Thu, 15 Apr 2010 17:59:57 -0700 (PDT), "lektric.dan(a)gmail.com"
> <lektric.dan(a)gmail.com> wrote:
>
>>I need help finding technology for a different kind of flow sensor. I
>>have a project where I need to monitor the flow of a ground organic
>>material (think oregano or pepper ground to 100-400 microns). It's
>>coming from a horizontal discharge tube (twin augers) down into a
>>vertical collector about 2" in dia. and 4" tall, then into a funnel
>>(with an opening just under 1/2"). There's a top on the collector
>>(everything's made of stainless), and everything is under 5-10 psi of
>>nitrogen. I need to 1) make sure the material is flowing down and
>>through the funnel, and 2) is not jammed up. I've got a
>>phototransister/IRLED set-up, and it can detect when the light beam is
>>blocked, but can't tell when there is a jam. Same with ultrasonic or
>>millimeter-wave radio (radar), a light beam reflective sensor, or a
>>capacitance/conductance sensor. I was thinking about some sort of
>>acoustic or impingement sensor (like a microphonic probe), but the gas
>>flow and feeder noise make that problematical, plus anything in the
>>stream can cause a plug/jam. Sensor needs to take up less than 1" of
>>process stream length.
>>
>>Ideas? Have I missed anything?
>
> Why not just make sure it doesn't jam? Eg a slowly rotating rough shaft
> or screw down through the middle?
>
> Cheers Tony

Reminds me of the rotating paddle type granular/powdered material
sensor. Usually these stall when material level reaches the sensor
level, but perhaps the same torque-monitored rotating paddle could both
sense material presence and help prevent or sense jamming.
From: Paul Hovnanian P.E. on 16 Apr 2010 19:40
Ultrasonic doppler.

--
Paul Hovnanian mailto:Paul(a)Hovnanian.com
------------------------------------------------------------------
Life would be so much easier if we could just look at the source code.
From: lektric.dan on 18 Apr 2010 00:13
Thanks to everyone that's replied. Each idea gave inspiration. I
just don't see how I can implement most of them, though. Here's a
picture, perhaps this will make the situation a little clearer. The
hopper is on the left. Twin augers feed horizontally. The vertical
cylinder and funnel are where the blockages occur, the augers go
almost all the way across cylinder. I can add on a very small piece
of tubung below the funnel, perhaps 1/2 - 1". Everything is rigid
plumbing, and because of the relationships between parts, just can't
be moved much.

picture: http://sites.google.com/site/lektricdan/home/feeder.jpg

I don't know if a single sensor will work. At high feed rates, the
free optical path (a clear shot across the tube) goes away. We would
like to run at as high a feed rate as possible. At lower feed rates,
where material is just trickled down, the free optical path is
intermittant, so a photo-type sensor and a missing pulse detector
circuit would work. For the higher feed rates (where the light path
would be blocked but material is flowing freely), I might need to add
a differential pressure sensor. As I mentioned in the original post,
the system is pressurized by from 5 to 10 psi, by nitrogen flowing
from the fitting at the top (with white teflon tape at the joint where
it fits into the top of the vertical section).
From: tm on 18 Apr 2010 00:32

<lektric.dan(a)gmail.com> wrote in message
news:49613f02-23dd-4517-9d49-38fc531e7882(a)b33g2000yqc.googlegroups.com...
>
> picture: http://sites.google.com/site/lektricdan/home/feeder.jpg
>
> I don't know if a single sensor will work. At high feed rates, the
> free optical path (a clear shot across the tube) goes away. We would
> like to run at as high a feed rate as possible. At lower feed rates,
> where material is just trickled down, the free optical path is
> intermittant, so a photo-type sensor and a missing pulse detector
> circuit would work. For the higher feed rates (where the light path
> would be blocked but material is flowing freely), I might need to add
> a differential pressure sensor. As I mentioned in the original post,
> the system is pressurized by from 5 to 10 psi, by nitrogen flowing
> from the fitting at the top (with white teflon tape at the joint where
> it fits into the top of the vertical section).

That is some awful welding :) or might just be the picture.

I liked the idea of using an optical mouse. Can you put a small
window in? The optical mouse has a very small video camera
that looks at the texture to detect motion and output pulses
for xy motion.

Cheap enough to try.


Tom




From: lektric.dan on 18 Apr 2010 02:01
On Apr 17, 11:32 pm, "tm" <no...(a)msc.com> wrote:

> That is some awful welding :) or might just be the picture.
>
It's a little of both. 316 stainless isn't the easiest stuff to weld,
and the machine shop we used had only a part-time welder. We've since
found a shop with a much better, full-time welder.

> I liked the idea of using an optical mouse. Can you put a small
> window in? The optical mouse has a very small video camera
> that looks at the texture to detect motion and output pulses
> for xy motion.
>
> Cheap enough to try.
>
I just did some googling on hacking laser mouses. I may be able to
look up the data sheets if I find identifiable ICs inside. Any
optical sensor (well, any I can think of anyway...) will need a
window, go this is a given. I'll try this next week and report back
how it worked (out of system - it's going to be a bit before we do a
tear-down and I have access to this part of the system).

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