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'[EE]:Infra-red Opto help'
2002\11\03@063805 by cdb

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I'm looking for suggestions for making a rain sensor using Infra- Red
techniques.

So far I've tried using a TIL139 emitter/detector package with very
little success and I've tried matched Schmidt trigger detector and
emitter form QT now Fairchild.
I have had better success with this except it only works face on
placing emitter and detector at 45 deg to each other with glass
perpendicular to both no result at all whether wet or dry.

Should I perhaps try a modulated approach - if I wanted a mud spatter
detector then no problems both setups work.

Failing this I thought of trying a different tack - Piezo sensor to
detect rain dropping on it -

This will be going to a PIC has anyone any other suggestions

Thanks

Colin
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cdb, spam_OUTcdbTakeThisOuTspambarnard.name on 31/03/2002

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2002\11\03@065547 by Jinx

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> I'm looking for suggestions for making a rain sensor using Infra-
> Red techniques.

Is this outside or inside looking out (glass ?)

a heated element like a thermistor - maybe for big drops

fine parallel lines on a PCB (gold-plated if outside) that short

a dew sensor from a VCR

frosted/etched glass that gets more transparent when wet

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2002\11\03@070828 by cdb

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Outside looking glass Jinx - to go with my sprinkler controller.

Yes the shorted PCB board not a problem an Oscillator  and a Schmitt
trigger, I just wanted to be different and possibly novel hence the
Piezo idea.

I'd wondered about a dew sensor, wasn't too sure if dew and water
were quite the same thing as far as the sensor was concerned.

But thanks for the suggestions - I see I can buy a ready made car
rain sensor from Bosch at $900 odd according to RS.

And I thought this would be so simple!

colin
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cdb, .....bodgy1KILLspamspam@spam@optusnet.com.au on 03/11/2002

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2002\11\03@112139 by David Harris

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Hi-
Howabout something that changes its resistance with moisture - maybe a
piece of black electrically conducting foam?
David

cdb wrote:

{Quote hidden}

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2002\11\03@123449 by Mike Singer

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David Harris
> Hi-
> Howabout something that changes its resistance with moisture - maybe a
> piece of black electrically conducting foam?
> David
>
> cdb wrote:
>
> > I'm looking for suggestions for making a rain sensor using Infra-
Red
> > techniques.

  Howabout something that changes its weight with moisture - maybe a
piece of foam? pressing down on a switch.

Mike.

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2002\11\03@155223 by Bill & Pookie

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----- Original Message -----
From: "Mike Singer" <.....msingerKILLspamspam.....POLUOSTROV.NET>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Sunday, November 03, 2002 8:35 AM
Subject: Re: [EE]:Infra-red Opto help


> > > I'm looking for suggestions for making a
rain sensor using Infra-
> Red
> > > techniques.

How about a transmitter/receiver set and hope that
the reflection of the rain drops will triger it?

Bill

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2002\11\03@161544 by Bob Axtell

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If you wish to measure the AMOUNT of rain, they normally capture it in a
decanter which you can then read optically or capacitively.

If you simply wish to detect ANY rain, an optical transmitter / receiver
spaced 3' apart would be blocked once rain actually started.

Interesting application.

--Bob Axtell
EDTec LLC
1-888-801-1416

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2002\11\03@175303 by Nate Duehr

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If there's a simple way to measure Relative Humidity, you could cheat
and just assume that it's raining or very close to doing so when the RH
was very high...?

Just a thought while I was sitting here reading... might be full of
holes...

Nate

On Sun, 2002-11-03 at 15:07, cdb wrote:
{Quote hidden}

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2002\11\03@181827 by cdb

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I hadn't considered electrical foam, though I had considered a cheap
strain gauge with the theory that rain must weigh something so if it
fell on the sensor etc, which is where the piezo idea came from.

This is just to detect rain. I've suddenly though that maybe I'm
using the wrong type of IR emitter so I'm going to try a high power
remote control type rather than a 4mm mouse wheel type.

Just one other question I am working on the assumption of a constant
beam with rain causing the beam to be either diminished or non
existent, but should I perhaps be looking at it the other way - no
beam and the rain causes reflectivity?

thanks for your help

Colin
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cdb, @spam@bodgy1KILLspamspamoptusnet.com.au on 04/11/2002

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2002\11\03@185016 by A.J. Tufgar

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How about a pcb with 2 traces close together that make a zigzag pattern
around the board?  When the rain hit the pcb it would cause a change in
resistance across the contacts.

Hope this helps,
Aaron

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2002\11\03@185841 by Dale Botkin

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I doubt seriously that would work.  I've seen the RH here at 97% and rthe
lawn still needed watering.

Dale
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Your ass will be laminated.

On Sun, 3 Nov 2002, Nate Duehr wrote:

> If there's a simple way to measure Relative Humidity, you could cheat
> and just assume that it's raining or very close to doing so when the RH
> was very high...?

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2002\11\03@190251 by Nate Duehr

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Yeah, I forgot... I'm in Denver where if the RH goes above 50% we're all
complaining about the humidity... (GRIN).

Nate

On Sun, 2002-11-03 at 16:56, Dale Botkin wrote:
{Quote hidden}

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2002\11\03@190705 by cdb

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I had thought about that as well, but here in Southern Queensland it
is sub tropical - so humidity can be high but no rain.

colin
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cdb, KILLspambodgy1KILLspamspamoptusnet.com.au on 04/11/2002

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2002\11\03@202904 by Rich

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I don't remember the exact wavelength, but there is a large peak in the IR
band for H2O, not far from the CO2 peak.  If you optically bandpass on the
H2O nm you may obtain the desired detection result.

Check out the IR band.
Good luck
Richard

{Original Message removed}

2002\11\03@222412 by Bill & Pookie

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Do people really pay for devices to automatic turn
on their wiper thingies so they don't have to
reach down and flick a switch?  Are these the same
people who don't know which way to look when
driving in the rain?

I would suggest that they stop the car on the
road, crawl underneath it and see if the road is
wet or dry.

I have found that a wet road smells like a wet
potato chip, if that is any help.

Pookie

ps   Bill's rain detector is to send me outside
and see if I come back wet.

----- Original Message -----
From: "cdb" <RemoveMEbodgy1TakeThisOuTspamOPTUSNET.COM.AU>
To: <spamBeGonePICLISTspamBeGonespamMITVMA.MIT.EDU>
Sent: Monday, November 04, 2002 2:06 AM
Subject: Re: [EE]:Infra-red Opto help

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2002\11\03@225050 by cdb

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How about a black ice detector ?

I've just semi -tried a wide angle remote control emitter and this
looks more promising.

>From an overcast and very humid Brisbane

Colin
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2002\11\03@232245 by Rich

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There is a H2O peak in the IR band not far from the CO2 peak.  An optical band pass filter at this nm range would detect the moisture from the rain.  It is a good humidity detector as well as a rain detector.  I have built such devices years ago.  It is easy to look up the IR spectrum for the H2O Peaks and choose the best one.  The detector sensitivity is also important.  
Richard

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2002\11\03@234608 by Jinx

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> I have found that a wet road smells like a wet
> potato chip, if that is any help.
>
> Pookie

I would have guessed peanuts but hey, you're the weirdo, it's
your call  ;-)

Colin, I wonder if old keyboard PCBs would do as sensors. They
have either gold-plated or carbon-film (eg remote control) matrices
that should be close enough to short when wet. Dunno how the
carbon ones would stand up to the UV in these here parts

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2002\11\04@082328 by Jeethu Rao

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Rich,
Where do you get these 'H2O band' IR band pass filters ? I've played
with
Gelatin filters, Dichroacs , AR Coated lenses etc , But never got to lay
My hands on anything IR.

Jeethu Rao

> {Original Message removed}

2002\11\04@100945 by Herbert Graf

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> Do people really pay for devices to automatic turn
> on their wiper thingies so they don't have to
> reach down and flick a switch?  Are these the same
> people who don't know which way to look when
> driving in the rain?
>
> I would suggest that they stop the car on the
> road, crawl underneath it and see if the road is
> wet or dry.
>
> I have found that a wet road smells like a wet
> potato chip, if that is any help.

       Actually, as silly as it sounds, the point of "rain detecting wipers" is
more than just turning them on. It's the rate of wiping that's important.
Often, when driving in stop and go traffic, one finds that while traveling
fast the wipers need to wipe more often, when travelling slower the wipers
don't need to wipe as often. When in stop and go traffic this becomes quite
annoying since you are constantly adjusting the speed of the wipers. Rain
sensing wipers do away with this problem by sensing when enough of the
windsheild is obscured and activate the wipers for one wipe. It is a feature
I truly wish I had on my car, I am in stop and go traffic quite often and
such a feature during moderate rainfall is a Godsend. TTYL

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2002\11\04@123210 by Peter L. Peres

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On Sun, 3 Nov 2002, Dale Botkin wrote:

*>I doubt seriously that would work.  I've seen the RH here at 97% and rthe
*>lawn still needed watering.

There are devices that measure the humidity in the ground. The list has
been there. Search the archives imho. Try 'gypsum cube humidity sensor'

Peter

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