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'Interfacing a PIC to HP infra-red serial port.'
1998\11\30@202647 by Don Holtz

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Does anyone have info on the serial protocol that HP uses to implement
their infra-red serial interface - for calculators and palmtops.

I have an HP-48S, and several HP palmtops that I would like to use to talk to
a PIC.

Any ideas?

Cheers,
Don


'Interfacing a PIC to HP infra-red serial port.'
1998\12\01@001039 by MattBeck
picon face
Not sure of the other methods used, but I know the HP48 series is half duplex
serial com. It is software timed, the acutal IR led, and IR phototransistor
are memory mapped. There is no modulation or demodulation to worry about but
range is limited to about 12". Just use a phototransistor to read and a IR led
to write to the Hp48 using normal (8,N,1) serial com. (2400baud max). Matt

1998\12\01@011315 by Lynx {Glenn Jones}

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One problem here, the HP's receiver circuitry is limited to only a couple
of inches, i guess to keep people from cheeting on tests, The transmit
range, however, is much farther, In fact i can use my hp to turn on my tv
from accross the room (more than 10ft). Also, the signals are inverted,
that is, no IR light means 1 while IR light means 0. Hope this helps. (I
myself am planning on interfacing my HP to a MCU using its IR
capabilities, but i havent tried anything yet.)

------------------------------------------------------------------------------
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On Tue, 1 Dec 1998 spam_OUTMattBeckTakeThisOuTspamAOL.COM wrote:

> Not sure of the other methods used, but I know the HP48 series is half duplex
> serial com. It is software timed, the acutal IR led, and IR phototransistor
> are memory mapped. There is no modulation or demodulation to worry about but
> range is limited to about 12". Just use a phototransistor to read and a IR led
> to write to the Hp48 using normal (8,N,1) serial com. (2400baud max). Matt
>

1998\12\01@063231 by Russell McMahon

picon face
I don't know if the latest HPs use the same protocol as the HP82240B
printer.
This is a 24 odd column standalone IR interfaced printer used with
the older IR capable calculators.

If they do, then the advice on this subject posted here seems to be
wrong. Perhaps the later units use a simpler protocol. If not, I can
help with the HP82240B protocol.HP can provide a very comprehensive
brochure on the protocol.

We connected to these directly for a vehicle based project but I also
tried using infra reed and it worked very successfully over  arrange
of 1 to 2 feet. More would have been easy. The serial protocol sends
bits which have a number of pulses of high or low depending on
whether a 1 or a 0. The pattern is not intuitive and is not straight
Manchester AFAIR. To convert to IR I simply gated the output of a 32
KHz oscillator using a 74C14 as the oscillator. HP say that the bits
must be synchronised with the 32 KHz signal but in my tests this did
not seem to be the case. In the limited tests that I did I got 100%
copy with asynchronous 32KHz oscillator. Also HPs specs for the
maximum and minimum number of 32 KHz pulses per bit suggest that I
was not violating this requirement.

I can probably turn up more details on the protocol if required -
this will not be the case if the other advice given is in fact
correct. Our system used an Atmel 2051 but I am (probably) not able
to release the code. PIC implementation should be easy. I looked at
an an IR version using a 6MHz ST6 but it was just too slow :-). PIC
should be easily fast enough to generate the 32KHz modulated pulses
directly.



regards




           Russell McMahon

From: Don Holtz <.....daholtzKILLspamspam@spam@AXIONET.COM>

>Does anyone have info on the serial protocol that HP uses to
implement
>their infra-red serial interface - for calculators and palmtops.
>
>I have an HP-48S, and several HP palmtops that I would like to use
to talk to
>a PIC.
>
>Any ideas?
>
>Cheers,
>Don
>

1998\12\01@103659 by Goovaerts

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This infrared that you use, does it implies the IrDA standard ?? Because I
have to implement IR following IrDA on a PIC16C63 !! If somebody sends you
some code, can you forward it to me ??
Thanks and greetings from Glenn Goovaerts !!!

{Original Message removed}

1998\12\01@112313 by Ricardo Seixas

picon face
Hi Don,

       The doc you need is located on http://www.hpcalc.org/docs/misc/io2.txt
       There's also a lot of docs, including I2C, HP48 -> modem, digital
osciloscope,
etc,etc, check it out.
       http://www.hpcalc.org/

Hope this helps

Ricardo Seixas


{Quote hidden}

1998\12\01@142551 by gwaiche

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Hi!

Remember that HP48s (If it's about this HP IR port we are
talking about) only knows the Kermit protocol.

Cheers!

Gael


MattBeckspamKILLspamAOL.COM wrote:
>
> Not sure of the other methods used, but I know the HP48 series is half duplex
> serial com. It is software timed, the acutal IR led, and IR phototransistor
> are memory mapped. There is no modulation or demodulation to worry about but
> range is limited to about 12". Just use a phototransistor to read and a IR led
> to write to the Hp48 using normal (8,N,1) serial com. (2400baud max). Matt

1998\12\01@151815 by Lynx {Glenn Jones}

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Im almost positive that the HP doesnt use IrDA, theres been quite a bit of
talk about this on the comp.sys.hp48 newsgroup. But since i dont know what
IrDA is exactly, i cant say for certain. I think that if you have a laptop
that uses IrDA, you can configure the laptop to talk to the HP, but thats
about as much as i know.

------------------------------------------------------------------------------
A member of the PI-100 Club:
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058209749445923078164062862089986280348253421170679

On Tue, 1 Dec 1998, Goovaerts wrote:

> This infrared that you use, does it implies the IrDA standard ?? Because I
> have to implement IR following IrDA on a PIC16C63 !! If somebody sends you
> some code, can you forward it to me ??
> Thanks and greetings from Glenn Goovaerts !!!
>
> {Original Message removed}

1998\12\01@153917 by Dennis Merrill

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I am pretty sure that the HP does not speak IrDA. It is simply a serial IR
link. Making the calculator speak IrDA would have been overkill for this
application, as it was not meant to have multiple connections. For info on
the HP, check out http://hp48.wsjr.com - I'm sure you can find the timing
diagrams and a description of the IR protocol there. Best of luck!

At 11:26 AM 12/1/98 -0800, you wrote:
>> >Does anyone have info on the serial protocol that HP uses to implement
>> >their infra-red serial interface - for calculators and palmtops.


-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Dennis Merrill, BSEE         work: .....merrillKILLspamspam.....nicolet.com
Firmware Engineer            home: EraseMEmerrillspam_OUTspamTakeThisOuTieee.org
Embedded Systems Group
Nicolet Instrument Corp.    phone: 608.276.6136

web: http://www.geocities.com/ResearchTriangle/5256
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=

1998\12\01@160307 by Lynx {Glenn Jones}

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Kermit is the file transfer protocal it uses, but it can also send
characters as raw ascii. I hope you can understand what im saying here.

------------------------------------------------------------------------------
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058209749445923078164062862089986280348253421170679

On Tue, 1 Dec 1998, Gael Waiche wrote:

{Quote hidden}

ed
> > to write to the Hp48 using normal (8,N,1) serial com. (2400baud max). Matt
>

1998\12\02@172501 by jmnewp

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Yea, I'm doing similar communication with the HP and my current
project.  It does NOT only know the kermit protocal, it may also use
asynchronos serial communication, at least through the wired port, I'm
not sure if it works with the IR port though.  The XMIT command sends a
string on the first level of the stack, the SRECV command takes the
number off of level one of the stack and receives that many characters
in the buffer, I've got some more prgramming info if you'd like it.  as
I just read in one of the replies, the IR port is also inverted so that
would require it to always be on (which would drain a bunch of power) in
an asychronos state of affairs, correct me if I'm wrong on that....


Jon

Don Holtz wrote:
{Quote hidden}

1998\12\02@185018 by Lynx {Glenn Jones}

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Works with both the IR port and the Wired port. also, it is inverted, that
is IR on means 0, but this doesnot take extra batt power because to start
sending, its sends an initial 0 to get things rolling.

------------------------------------------------------------------------------
A member of the PI-100 Club:
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058209749445923078164062862089986280348253421170679

On Wed, 2 Dec 1998, MARK D NEWPORT wrote:

{Quote hidden}

1998\12\04@121258 by Jurva-Markus Vehasmaa

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You micht be interestet on Maxims MAX3100 uart. http://www.maxim-ic.com
It suports IrDA protocol.


----------
From: Goovaerts <@spam@goofy1KILLspamspamGLO.BE>
To: KILLspamPICLISTKILLspamspamMITVMA.MIT.EDU
Subject: Re: Interfacing a PIC to HP infra-red serial port.
Date: 1. joulukuuta 1998 17:34

This infrared that you use, does it implies the IrDA standard ?? Because I
have to implement IR following IrDA on a PIC16C63 !! If somebody sends you
some code, can you forward it to me ??
Thanks and greetings from Glenn Goovaerts !!!

{Original Message removed}


'[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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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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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" <RemoveMEmsingerspamTakeThisOuTPOLUOSTROV.NET>
To: <PICLISTEraseMEspam.....MITVMA.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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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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Fusistance is retile.
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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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}

'[EE]:Infra-red Opto ... What about X-band RF Dopp'
2002\11\03@204150 by Jim

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Here's a wild one - what about using one of those
simple X-band, Gunn-diode Doppler units that are
used as motion detectors?

Experimenting with a low-power Gunn-diode based,
X-band Doppler RADAR (police speed RADAR) unit a
few years ago during the onset of rain I noticed
was able to 'hear' (they supply the recovered Doppler
shift to a speaker on the unit) the 'precip' as it
fell ... sort of a whistling sound ...

This was done by looking 'up' through the roof of
my garage ... the roof was covered with the usual
'composition shingles' and the actual ceiling in
the garage was composed of sheet rock (gypsum
board).

RF Jim

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'[EE]:Infra-red Opto help'
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.

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To: <EraseMEPICLISTspamspamspamBeGoneMITVMA.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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'[EE]:rain Sensors, was Infra-red Opto help'
2002\11\04@053031 by Alan B. Pearce

face picon face
>which is where the piezo idea came from.

What happens if you have a piezo speaker as the resonant element in an
oscillator? When a rain drop lands on it will the resonant frequency or
amplitude change enough to detect? The only problem I see with this method
is that the electrodes would need protecting against the moisture.

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'[EE]:Infra-red Opto ... What about X-band RF Dopp'
2002\11\04@053653 by cdb

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good idea and it could double also warn me of low flying Policemen.

I had pondered on playing with a PIR out of security wotsit - but I'm
looking for something that is relatively cheap and repeatable. The
capacitive/shorted PCB/Probe will be my last resort mainly because
it's easy to do and most other people use it - I like to be
differentish.

colin
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'[EE]:rain Sensors, was Infra-red Opto help'
2002\11\04@054316 by cdb

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Possible, what I thought was get one of those Piezo's that are in a
coin holder looking affair - about $3.00 here, fix it into a
waterproof box with a bolt glued to its backside - this would make
the Piezo very sensitive to vibration -ergo when rain falls on it
vibration happens voltage occurs. I think I've seen water proof Piezo
tweeters somewhere so they might work.

Just disappointed that I can't get the Opto bit to work - must try
some crazed glass see if that makes a difference.

colin
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2002\11\04@060206 by Alan B. Pearce

face picon face
>this would make the Piezo very sensitive to vibration -ergo
>when rain falls on it vibration happens voltage occurs. I
>think I've seen water proof Piezo tweeters somewhere so they
>might work.

I was not thinking of having it like that, I was figuring on having the
piezo unit driven at low level by being the tuned element in an oscillator,
and a PLL to look for frequency shift, or some form of amplitude detection
to look for amplitude damping. It may be that if the level of oscillation is
controlled at a low enough level, then a drop of rain may be enough to make
the piezo element go low enough in Q, or be damped enough to cause it to
drop out of oscillation.

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2002\11\04@061024 by cdb

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Yes, that would probably work - I'll try that one - as a separate
project. otherwise I'll have to rewrite my software - the present
problem is intended as a retro-fit using the least amount of add on
components - though I'll probably still have to use a comparator as
the detectors doesn't 'snap' between voltage levels as I had hoped it
would.

Mind you I could perhaps have it as an arm in the timing chain of a
555  hmm

Colin
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'[EE]:Infra-red Opto help'
2002\11\04@082328 by Jeethu Rao

flavicon
face
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

flavicon
face
> 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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'[EE]:Infra-red Opto ... Windshield-Wiper aides'
2002\11\04@101824 by Jim

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A big part of the problem is the affinity that water
has for glass and it 'sticks' to the glass distorting
the image seen through that glass -

- a product called "RainX" changes that 'like' to a
'dislike' and the water beads up and quite literally
balls up and 'rolls off'.

I highly recommend it for long trips (in the rain) - or
for when your wipers have died and it isn't practical to
effect a repair right away. Using RainX *almost* removes
the need for wipers at all ...

RF Jim

{Original Message removed}

2002\11\04@104513 by Alan B. Pearce

face picon face
>- a product called "RainX" changes that 'like' to a
>'dislike' and the water beads up and quite literally
>balls up and 'rolls off'.
>
>I highly recommend it for long trips (in the rain) - or
>for when your wipers have died and it isn't practical to
>effect a repair right away. Using RainX *almost* removes
>the need for wipers at all ...

I do not know how much this product costs, but I used to like the way the
rain wiped off after the car had been through an aiutomtic auto wash with
wax and dry for this reason. Probably cheaper too :)))

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'[EE]:Infra-red Opto help'
2002\11\04@123210 by Peter L. Peres

picon face
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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'[EE]:rain Sensors, was Infra-red Opto help'
2002\11\04@123216 by Peter L. Peres

picon face
On Mon, 4 Nov 2002, Alan B. Pearce wrote:

*>>this would make the Piezo very sensitive to vibration -ergo
*>>when rain falls on it vibration happens voltage occurs. I
*>>think I've seen water proof Piezo tweeters somewhere so they
*>>might work.
*>
*>I was not thinking of having it like that, I was figuring on having the
*>piezo unit driven at low level by being the tuned element in an oscillator,
*>and a PLL to look for frequency shift, or some form of amplitude detection
*>to look for amplitude damping. It may be that if the level of oscillation is
*>controlled at a low enough level, then a drop of rain may be enough to make
*>the piezo element go low enough in Q, or be damped enough to cause it to
*>drop out of oscillation.

Spent too much time in aerospace ? ;-) A raindrop falls from at least 500
meters of height and has a minimum size. I'd use a simple microphone
attached to a drum-like structure (with saran wrap skin I think). This may
react to other things besides rain.

I still favor the idea of measuring just soil humidity.

Peter

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2002\11\04@133842 by Francisco Ares

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Take a look at Bosch's rain sensor at

http://app3.internetwork-bosch.com/webapp/kea/k/en/start/product.jsp?mfacKey=BE_5_REGENS

and also

http://www.schott.com/magazine/english/info96/si096_12_sensor.html

hope this helps
Francisco


Peter L. Peres wrote:

{Quote hidden}

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'[EE]:Infra-red Opto ... Windshield-Wiper aides'
2002\11\04@134050 by Peter L. Peres

picon face
On Mon, 4 Nov 2002, Alan B. Pearce wrote:

*>I do not know how much this product costs, but I used to like the way the
*>rain wiped off after the car had been through an aiutomtic auto wash with
*>wax and dry for this reason. Probably cheaper too :)))

Did you say WAX ? ;-)

Peter

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2002\11\04@143813 by Herbert Graf

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> A big part of the problem is the affinity that water
> has for glass and it 'sticks' to the glass distorting
> the image seen through that glass -
>
> - a product called "RainX" changes that 'like' to a
> 'dislike' and the water beads up and quite literally
> balls up and 'rolls off'.
>
> I highly recommend it for long trips (in the rain) - or
> for when your wipers have died and it isn't practical to
> effect a repair right away. Using RainX *almost* removes
> the need for wipers at all ...

       Well I can definately add my vote for RainX, that stuff is a wonder. I use
it in the "windshild washer fluid" form, it costs about twice the cost of
"normal" fluid but it's worth it. ESPECIALLY in the winter, snow barely
sticks to the stuff. TTYL

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'[EE]:rain Sensors, was Infra-red Opto help'
2002\11\04@151645 by Bill & Pookie

picon face
Looks like the question might be "How do I tell
how well the wipers are keeping the windshield
clear?"

This could require a device looking through the
windshield.   A simple IR system used for remote
controls, with the transmitter just outputting
pulses and the receiver detecting the lack of
pulses might work if the rain on the windshield
would scatter the IR enuff.

I will test this theory first rain I get.  Can
strap my BoomBox on the hood and see how well the
remote control works in the rain.  And will start
looking for a IR transmitting hood ornament.

Bill


{Original Message removed}

'[EE]:Infra-red Opto ... Windshield-Wiper aides'
2002\11\04@165530 by Jonathan Johnson

flavicon
face
It's about $10-15 Australian a bottle and works brilliantly, even builds up
on your glass so it works better over time...

> {Original Message removed}

'[EE]:rain Sensors, was Infra-red Opto help'
2002\11\05@055307 by Alan B. Pearce

face picon face
>Spent too much time in aerospace ? ;-)

Yeah possibly :)))

>A raindrop falls from at least 500 meters of height and has
>a minimum size. I'd use a simple microphone attached to a
>drum-like structure (with saran wrap skin I think). This may
>react to other things besides rain.

Well yeah, if it is actually raining, in a "cats and dogs" sense. But often
when I'm driving my car, the road is wet, and there is misty water landing
on the wind screen, so there is some precipitation of moisture out of the
atmosphere. It certainly does not land on the windscreen with enough energy
to make any noise.

I guess if all your trying to do is determine if the lawn needs watering,
then this will not be enough moisture to count :)

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2002\11\05@060725 by Russell McMahon

face
flavicon
face
> >A raindrop falls from at least 500 meters of height and has
> >a minimum size. I'd use a simple microphone attached to a
> >drum-like structure (with saran wrap skin I think). This may
> >react to other things besides rain.
>
> Well yeah, if it is actually raining, in a "cats and dogs" sense. But
often
> when I'm driving my car, the road is wet, and there is misty water landing
> on the wind screen, so there is some precipitation of moisture out of the
> atmosphere. It certainly does not land on the windscreen with enough
energy
> to make any noise.

FWIW - a raindrop has a terminal velocity of a few tens of kilometres per
second. Actual velocity depends on drop size but in free fall is never vast.
I imagine that wind blown drops assume a speed approaching that of the wind
gust they are carried by.



       RM

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2002\11\05@062837 by Jan-Erik Soderholm

face picon face
Well, ait depends.

*You* (as standing formly on the ground) beleive that the raindrop
is moving horizontaly. But the *raindrop* itself don't understand that
there is a wind, since it moves along with the wind itself. It thinks that
it's the earth below it that has begun rotating in the opposit direction.

So, it depends how you messure, as always.

And when it commes to the "speed" of the raindrop, the speed trought
the air has, as you said, a terminal velocity, and that speed is always
straigt verticaly, as seen from the surounding air ! Now,  if messured from
the ground, and if there's a "wind" the raindrop will have a horizontal speed
as well as the (constant) vertical speed. The speed-through-air, is constant,
but by doing some vector mathematics, one can calculate the speed-over-ground,
that, with any wind > 0, always will be higher then when it's calm.

So, when driving you car, it's not the raindrop that hits you, it's you
that hits the raindrop...

Anyway, there is a book that describes this better written by someone
called Albert Einstein...

:-)

Jan-Erik Svderholm.

>FWIW - a raindrop has a terminal velocity of a few tens of kilometres per
>second. Actual velocity depends on drop size but in free fall is never vast.
>I imagine that wind blown drops assume a speed approaching that of the wind
>gust they are carried by.
>
>
>
>       RM


Jan-Erik Svderholm
S:t Anna Data
tel : +46 121 42161
mob : +46 70 5241690

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2002\11\05@080021 by cdb

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face
>FWIW - a raindrop has a terminal velocity of a few tens of
>kilometres per second

So I should abandon my opto attempt and try a microwave radar gun
instead perhaps :) ?


colin
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2002\11\05@080842 by Olin Lathrop

face picon face
> FWIW - a raindrop has a terminal velocity of a few tens of kilometres
per
> second.

Around here they go *much* slower.  At mach 30 or so the sonic booms must
get rather annoying.


*****************************************************************
Embed Inc, embedded system specialists in Littleton Massachusetts
(978) 742-9014, http://www.embedinc.com

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2002\11\05@081503 by Michael Rigby-Jones

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{Quote hidden}

Surely tens of *meters* rather than kilometers?

Mike

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2002\11\05@092403 by Mike Singer

picon face
Olin Lathrop wrote:
> > Peter L. Peres wrote:
> > FWIW - a raindrop has a terminal velocity of a few tens
> > of kilometres per second.
>
> Around here they go *much* slower.  At mach 30 or so the
> sonic booms must get rather annoying.


Peter L. Peres COULD reply with Olin's words:
> Yes, you are absolutely right.  I noticed that my statement
> was a bit misleading right after I sent it and wondered if
> some wiseass would bother point it out <g>.


  Congratulations.
  Mike.

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2002\11\05@161151 by Jinx

face picon face
> FWIW - a raindrop has a terminal velocity of a few tens of kilometres
> per second.
>
>         RM

WOW !!!! Is that how hard it rains inTe Atatu ? You must all have council-
issue armour-plated hats

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2002\11\05@164313 by Russell McMahon

face
flavicon
face
> > FWIW - a raindrop has a terminal velocity of a few tens of kilometres
per
> > second. Actual velocity depends on drop size but in free fall is never
> > vast.

> Surely tens of *meters* rather than kilometers?

Whoops - yes
Tens of kilometres per hour that should have said.
Tens of kilometres per second gets you into space :-)



       RM

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2002\11\05@171759 by Peter L. Peres

picon face
On Tue, 5 Nov 2002, Mike Singer wrote:

*>> > Peter L. Peres wrote:
*>> > FWIW - a raindrop has a terminal velocity of a few tens
*>> > of kilometres per second.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

I did not write that. Please clip carefully next time.

Peter

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2002\11\05@234101 by Mike Singer

picon face
Sorry.

> On Tue, 5 Nov 2002, Mike Singer wrote:
>
> *>> > Peter L. Peres wrote:
> *>> > FWIW - a raindrop has a terminal velocity of a few tens
> *>> > of kilometres per second.
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>
> I did not write that. Please clip carefully next time.
>
> Peter

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2002\11\06@005736 by Mike Singer

picon face
  What do spoil the view of a road?  Drops on the
glass, refracting light beams. Let's us use the
refraction.
  1. Let some opto-emitter illuminate the glass at
an angle of about 30 degrees
  2. Then let a set (matrix) of opto-receivers receive
the resulting picture (90 degrees maybe). When the
glass is clear, store in memory the receivers' outputs.
  3. When drops have spoiled the picture, receivers'
outputs should got different from stored in memory,
provided they have proper focus (curved inwards,
may be) to catch drops' refraction.
  Get the standard deviation or what the heck is
appropriate in this case and decide if the view got
spoiled enough to start cleaning.

Mike.

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