Prox sensor
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Dear stampers,
Not really off topic because they will be connected to stamps!
I am looking for a circuit that will be suitable to detect the presence of a
granular fertilizer in a storage silo. Just need a go/no-go type output eg
whether the sensor is covered or not.
Anyone got a suitable circuit?
Tim Stockman
[noparse][[/noparse]Non-text portions of this message have been removed]
Not really off topic because they will be connected to stamps!
I am looking for a circuit that will be suitable to detect the presence of a
granular fertilizer in a storage silo. Just need a go/no-go type output eg
whether the sensor is covered or not.
Anyone got a suitable circuit?
Tim Stockman
[noparse][[/noparse]Non-text portions of this message have been removed]
Comments
as the fertilizer would corode any exposed connections. A flap with a
microswitch would work also, but it would have to be sealed also. I don't
recall seeing an off-the-shelf sensor for this, but I'm sure some of the
industrial / batch people may know of one.
Original Message
> I am looking for a circuit that will be suitable to detect the
presence of a granular fertilizer in a storage silo. Just need a go/no-go
type output eg whether the sensor is covered or not.
>
> Anyone got a suitable circuit?
need to set the sensor back into the tube a bit and use a window that does
not reflect so much to be read. The concern would be that the window surface
would become abraded or dusty and give a false positive. How far is the
distance across the silo where you want to measure? If it is near an
constriction, you may be able to put a separated pair and shoot from one side
to the other.
If there is normally light inside the silo then a photovoltaic cell would
potentially work.
you need to detect. And what sort of granular size.
For reliable detection I'd suggest some sort of vibrating
assembly [noparse][[/noparse]could be piezo] - the frequency and energy it
takes to drive it would vary as it was surrounded with
material. This assumes that the sensor enclosure material is
flexible. The vibration would also tend to clean dust off.
Is the stuff flammable? [noparse][[/noparse]static electric charge could be
an issue].
For just pressure you could have a capacitive bridge with
grounded outer plates which would squeeze toward an inner
plate. Here the issue would be what would stay uniform over
time squeezing and un squeezing. Perhaps silicone rubber
between aluminum plates would work.
Interlink Electronics has resistive material which changes
with pressure on it.
There are membrane elastomers used in keyboards which change
resistance with pressure.
Without knowing how much pressure - min and max - you are
trying to work with it's all up in the guessing region.
>>
Date: Fri, 6 Jul 2001 08:28:42 +0930
From: "Tim Stockman, STOCKMAN ELECTRONICS" <stocky@c...>
...
I am looking for a circuit that will be suitable to detect the presence
of a granular fertilizer in a storage silo. Just need a go/no-go type
output eg whether the sensor is covered or not.
<<
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Is this silo used to store this material exclusively? If so,
could you use sonar to determine the presence of this material
and a the volume as well?
George B.
--- In basicstamps@y..., s premena <premzee@j...> wrote:
> It would help if you could give the minimum amount of weight
> you need to detect. And what sort of granular size.
>
> For reliable detection I'd suggest some sort of vibrating
> assembly [noparse][[/noparse]could be piezo] - the frequency and energy it
> takes to drive it would vary as it was surrounded with
> material. This assumes that the sensor enclosure material is
> flexible. The vibration would also tend to clean dust off.
> Is the stuff flammable? [noparse][[/noparse]static electric charge could be
> an issue].
>
> For just pressure you could have a capacitive bridge with
> grounded outer plates which would squeeze toward an inner
> plate. Here the issue would be what would stay uniform over
> time squeezing and un squeezing. Perhaps silicone rubber
> between aluminum plates would work.
>
> Interlink Electronics has resistive material which changes
> with pressure on it.
>
> There are membrane elastomers used in keyboards which change
> resistance with pressure.
>
> Without knowing how much pressure - min and max - you are
> trying to work with it's all up in the guessing region.
>
>
> >>
> Date: Fri, 6 Jul 2001 08:28:42 +0930
> From: "Tim Stockman, STOCKMAN ELECTRONICS" <stocky@c...>
> ...
> I am looking for a circuit that will be suitable to detect the
presence
> of a granular fertilizer in a storage silo. Just need a go/no-go
type
> output eg whether the sensor is covered or not.
> <<
>
> ________________________________________________________________
> GET INTERNET ACCESS FROM JUNO!
> Juno offers FREE or PREMIUM Internet access for less!
> Join Juno today! For your FREE software, visit:
> http://dl.www.juno.com/get/tagj.
A person could try constructing two plates in proximity,
maybe you could detect a difference in capacitance when the
material becomes the dielectric verses air? If it worked, dirt
and dust would not be a problem, gravity would remove the material
when plates are placed vertical.
George B.
--- In basicstamps@y..., gbrecke@y... wrote:
> I'm not sure the goal has been well established yet.
>
> Is this silo used to store this material exclusively? If so,
> could you use sonar to determine the presence of this material
> and a the volume as well?
>
> George B.
>
>
> --- In basicstamps@y..., s premena <premzee@j...> wrote:
> > It would help if you could give the minimum amount of weight
> > you need to detect. And what sort of granular size.
> >
> > For reliable detection I'd suggest some sort of vibrating
> > assembly [noparse][[/noparse]could be piezo] - the frequency and energy it
> > takes to drive it would vary as it was surrounded with
> > material. This assumes that the sensor enclosure material is
> > flexible. The vibration would also tend to clean dust off.
> > Is the stuff flammable? [noparse][[/noparse]static electric charge could be
> > an issue].
> >
> > For just pressure you could have a capacitive bridge with
> > grounded outer plates which would squeeze toward an inner
> > plate. Here the issue would be what would stay uniform over
> > time squeezing and un squeezing. Perhaps silicone rubber
> > between aluminum plates would work.
> >
> > Interlink Electronics has resistive material which changes
> > with pressure on it.
> >
> > There are membrane elastomers used in keyboards which change
> > resistance with pressure.
> >
> > Without knowing how much pressure - min and max - you are
> > trying to work with it's all up in the guessing region.
> >
> >
> > >>
> > Date: Fri, 6 Jul 2001 08:28:42 +0930
> > From: "Tim Stockman, STOCKMAN ELECTRONICS" <stocky@c...>
> > ...
> > I am looking for a circuit that will be suitable to detect the
> presence
> > of a granular fertilizer in a storage silo. Just need a go/no-go
> type
> > output eg whether the sensor is covered or not.
> > <<
> >
> > ________________________________________________________________
> > GET INTERNET ACCESS FROM JUNO!
> > Juno offers FREE or PREMIUM Internet access for less!
> > Join Juno today! For your FREE software, visit:
> > http://dl.www.juno.com/get/tagj.
I've read a few replies, some suggest interrupting a light beam in
one way or another, I think I saw something about a flap and
microswitch. Here is my 2 cents:
Ultrasonics- Use a pair of piezo speakers, one as a speaker, the
other as a pickup (microphone.) Place the "microphone" at the top of
the silo, place the "speaker" where it would be an inch or two
beneath the fertilizer (at its maximum desired level). Cover both the
speaker and microphone with something that will protect them both,
without adding attenution. (plastic)
When the fertilizer covers the speaker the microphone misses the
ultrasonic pulses the speaker produces. This scheme would probably
work with audio, but, you may hear the thing work, or worse, ambient
noise may prevent the system from working. This may be less of a
problem with ultrasonics.
Electronic overview:
operating frequency: not terribly importamt, 25Khz or so. Speaker
driven by 555, square wave output ok, no driver xstr necessary. Run
555 at 12 volts.
Receiver: ultrasonic speaker, amplified (op-amp for gain, hi-pass)
then rectified and inverted. Provides clock pulse for monostable 555.
Here's what happens.
silo level low: speaker provides occasional pulse. Microphone detects
pulse and turns on 555. Next pulse comes before 555 turns off. So
long as pulses are detected the 555 never turns off.
Silo fills up:
Fertilizer covers piezo speaker. Microphone no longer detects pulses.
555 stops getting trigger pulses, 555 turns off shortly after. The
555 output corrosponds to the level of fertilizer in the silo.
Sort of a "missing pulse detection" scheme. When the 555 outputs low
the fertilizer is at its threshold level in the silo. Running the 555
used in the "receiver" at 5 volts allows direct connection of the 555
output to your stamp. (Where would we all be without the 555?)
If I had a silo of my own I would do this.
Regards
Rich
--- In basicstamps@y..., "Tim Stockman, STOCKMAN ELECTRONICS"
<stocky@c...> wrote:
> Dear stampers,
>
> Not really off topic because they will be connected to stamps!
>
> I am looking for a circuit that will be suitable to detect the
presence of a granular fertilizer in a storage silo. Just need a
go/no-go type output eg whether the sensor is covered or not.
>
> Anyone got a suitable circuit?
>
>
> Tim Stockman
>
>
> [noparse][[/noparse]Non-text portions of this message have been removed]