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'ph and CO2 measurers?'
1998\03\24@221426 by Robert Walker

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Howdy,



       I am interested in finding some information for a PIC project.

       Is there a sensor that can measure pH that is cheapish and can
       say be connected to a PIC (similar to a DS1820 temp chip)?

       Also, is there a sensor which can measure the amount of CO2 gas
       in a given area?? again, it would be good to connect this to a PIC
       chip.

       The reason is that I am interested in starting a little hydroponics
       set up, and any information on these (including the hydroponics :-))
       would be of great help.


Regards,


Rob Walker.

1998\03\25@022756 by Peter Neubert

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Hi Robert

Regarding pH Sensor there are a few available i dont know from where :-) but
what you are looking at is meausuring conductivity between to probes -

Regarding CO2 sensor - thios is worse - I think you can by some some very
expensive chemical sensors how they work I dont know but there is another
solution to this problem.
CO2 has this strange property which makes it absorb infrared light at a
ceratin wavelength (I think 490 nm - check it out, I am really Really not
sure about this)  The solution then is to build a transmitter and a receiver
and measusure what Not coming through, This will give you an indication of
the CO2 amount in the air - a few problems however exists:

1. finding a LED which emits in that spectrum
2. Finding a Ligth sensitive diode which only responds in this spectrum - I
think a uk company manufatures diodes for this range Or You can get an
optical filter for the selected spectrum - you must make sure to get the
rigth componenets as you dont wnat to measure water vapor or whatever
happends to be between the LED and the SENSOR
3. LED driving circuit - normally the LED's of this kind must be pulsed in
order to get the maximal output - a suitable power transistor circuit must
be build
4. Temperature - These specialised Diodes are usually very temperature
sensitive so some kind of chopping might be needed- Here you can use the
fact that the diode must be pulsed anyway and make a sort of electronic
chopping :-) where you meassure the output from the receiver when the diode
is not running - this will give you a value dependent of the temperature -
puls the diode for a while and look at your input - with theese 2 values +
some calibration data etc you should know be able to calculate the CO2
amount in the air with a good precision - at the same time you avoid to
build ekstra circuits for temperature compensation.
5. CO2 is - what many people dont know - very dangerous - and a
concentration of just 10% will cause unconsciousness - remember this when
you calibrate your circuit :-) It will make your plants grow - but be maybe
not you  :-)


The above solution should work - I did it once many years ago as a project
during my studies
I believe with proper chosen componenets (PIC etc ) you should be able to
keep the cost down to less than say 150$ fro the total circuit - There are
comercial available products doing exactly this - but they are priced much
much higher

feel free to share all your future earnings with me :-)

regards

Peter Neubert
Mauritius


{Quote hidden}

:-))
>        would be of great help.
>
>
>Regards,
>
>
>Rob Walker.
>

1998\03\25@082644 by Keith Howell

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Robert Walker <spam_OUTRobert.WalkerTakeThisOuTspamAIRSERVICES.GOV.AU> wrote:

> Is there a sensor that can measure pH that is cheapish and can
> say be connected to a PIC (similar to a DS1820 temp chip)?
> Also, is there a sensor which can measure the amount of CO2 gas
> in a given area?? again, it would be good to connect this to a PIC
> The reason is that I am interested in starting a little hydroponics
> set up, and any information on these (including the hydroponics :-))
> would be of great help.

I'm curious as to why anyone would wish to grow anything hydroponically
in a country with the climate of a greenhouse. Most of the population
is coastal and water is not _that_ scarce.

Hmm... call me Mr. Cheeky if you like, but you're not trying to set up
a cannabis growing establishment are you? I've seen ads for hydroponics
kits, usually selling halide lamps, etc. Somebody's got to want a plant
really badly if they want to force-feed it light and carbon dioxide.

Apologies if you're not, but you could always check out one of these
places. I'm sure they'll listen to your legitimate reasons for buying
it, and say "sure, what you do with it is not our business".

So, what are you up to?

Yours curiously, Mr. Cheeky.

1998\03\25@095733 by Bob Fehrenbach

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Peter Neubert <.....neubertKILLspamspam@spam@BOW.INTNET.MU> wrote:
>CO2 has this strange property which makes it absorb infrared light at a
>ceratin wavelength (I think 490 nm - check it out, I am really Really not

  The wave length in question is at least ten times longer than this,
  more like 5000 nm.


>1. finding a LED which emits in that spectrum

  Normally an incandescent lamp is used.

>2. Finding a Ligth sensitive diode which only responds in this spectrum - I

  There are photo detectors and filters made for this use but they are
  expensive and temperature sensitive.  Either the sensor must be in a
  temperature controlled environment (Peltier coolers are one common
  technique) or temperature compensation must be incorporated in the
  softare.

  Typically, the light beam is chopped by a rotating disk, which tends
  to raise the complexity out of the range of a hobby type application.


  Quantifying CO2 is a non-trivial problem.

>3. LED driving circuit - normally the LED's of this kind must be pulsed in

  Forget LEDs.  They are not available in the wavelengths that are
  absorbed by CO2.

>5. CO2 is - what many people dont know - very dangerous - and a
>concentration of just 10% will cause unconsciousness - remember this when

  Are you confusing this with carbon MONoxide?  Your expired breath
  typically contains 5% CO2.


--
Bob Fehrenbach    Wauwatosa, WI     bfehrenbspamKILLspamexecpc.com

1998\03\25@104657 by Morgan Olsson

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>>concentration of just 10% will cause unconsciousness - remember this when
>
>   Are you confusing this with carbon MONoxide?  Your expired breath
>   typically contains 5% CO2.

In school I learned 7% CO2 is dangerous.
CO is *much* more dangerous, rather poison.

/Morgan
/  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
\  .....mrtKILLspamspam.....iname.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\03\25@115809 by Sean Breheny

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At 04:35 PM 3/25/98 +0100, you wrote:
>>>concentration of just 10% will cause unconsciousness - remember this when
>>
>>   Are you confusing this with carbon MONoxide?  Your expired breath
>>   typically contains 5% CO2.
>
>In school I learned 7% CO2 is dangerous.
>CO is *much* more dangerous, rather poison.

As far as I know, there are three ways in which CO2 can cause problems:

1.) It can be of such high concentration that it dilutes the oxygen in the
air you are breathing to an extent that you do not receive enough oxygen.
The concentration of CO2 necessary for this would depend on the amount of
02 in the air.

2.) It can cause you to hyperventilate and not take deep enough breaths to
get enough 02 (this is because pH of the blood is measured by the brain and
is used to determine breathing frequency. The pH is primarily affected by
C02 concentration)

3.) It might be able to increase the acidity of your blood to a high enough
level that it would affect the operation of hemoglobin and other vital
blood chemicals. I am not sure how much CO2 would be needed for this.

As with any experiment, it is not a good idea to expose yourself to any
environment significantly foreign from what you normally experience. Use a
well ventilated area and enclose the area which contains the C02, and you
should be fine, I would think.

Sean (not a physiology or pharmicology expert!)


+--------------------------------+
| Sean Breheny                   |
| Amateur Radio Callsign: KA3YXM |
| Electrical Engineering Student |
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1998\03\25@122150 by Justin Crooks

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I have seen studies where up to 35% CO2 was mixed with sufficient oxygen,
and breathed comfortably for quite some time.  I think the only danger of
CO2 is that it typically is the byproduct of an oxygen-consuming reaction,
and therefore there is insufficient oxygen to sustain consciousness (and/or
life).

For what it's worth...

----------
> From: Morgan Olsson <mrtspamspam_OUTINAME.COM>
> To: @spam@PICLISTKILLspamspamMITVMA.MIT.EDU
> Subject: Re: ph and CO2 measurers?
> Date: Wednesday, March 25, 1998 8:35 AM
>
> >>concentration of just 10% will cause unconsciousness - remember this
when
> >
> >   Are you confusing this with carbon MONoxide?  Your expired breath
> >   typically contains 5% CO2.
>
> In school I learned 7% CO2 is dangerous.
> CO is *much* more dangerous, rather poison.
>
> /Morgan
> /  Morgan Olsson, MORGANS REGLERTEKNIK, SE-277 35 KIVIK, Sweden \
> \  KILLspammrtKILLspamspaminame.com, ph: +46 (0)414 70741; fax +46 (0)414 70331    /

1998\03\25@125737 by John Halleck

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On Wed, 25 Mar 1998, Morgan Olsson wrote:

> >>concentration of just 10% will cause unconsciousness - remember this when

The Biosphere II project was over 10% CO2, as pointed out in the national
and international press.  In the interviews they didn't look unconscious
to me.

{Quote hidden}

1998\03\25@182044 by Brian Gracia

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At 01:03 PM 3/25/98 +1000, you wrote:
{Quote hidden}

For hydroponics, join the hydroponics mail list.  See:

This list is for the discussion of anything related to hydroponic
gardening, including methods, systems, nutrients, plants, greenhouses,
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1998\03\26@015953 by Peter Neubert

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Bob wrote a few things I would like to comment on:



>Peter Neubert <EraseMEneubertspamspamspamBeGoneBOW.INTNET.MU> wrote:
>>CO2 has this strange property which makes it absorb infrared light at a
>>ceratin wavelength (I think 490 nm - check it out, I am really Really not
>
>   The wave length in question is at least ten times longer than this,
>   more like 5000 nm.


As I said - cant remember - however look a bit further down in this text

>
>>1. finding a LED which emits in that spectrum


>   Normally an incandescent lamp is used.


For 5000 nm yes maybe :-)


>
>>2. Finding a Ligth sensitive diode which only responds in this spectrum -
I
>
>   There are photo detectors and filters made for this use but they are
>   expensive and temperature sensitive.  Either the sensor must be in a
>   temperature controlled environment (Peltier coolers are one common
>   technique) or temperature compensation must be incorporated in the
>   softare.

Yes you are rigth - however they are availble from specialist companies and
the prices
are not as high as you think - actually the price of an optical filter is
higher than a specialised photo detector


{Quote hidden}

Well this is where you are wrong - as I said i did this once as a project at
Loughborough University - and they are available

>>5. CO2 is - what many people dont know - very dangerous - and a
>>concentration of just 10% will cause unconsciousness - remember this when
>
>   Are you confusing this with carbon MONoxide?  Your expired breath
>   typically contains 5% CO2.

Nope !  as you write yourself Your expired breath
  typically contains 5% CO2 - then you would agree that it would be a bit
difficult for the body to get rid of its own surplus CO2 if the surrounding
concentrations are high :-) causing hyperventilation, dizziness and
eventually you would be lying on the floor




--------------------------

Please read the following cut/paste from http://sablesys.com/ca1.html

Please note i dont work for the company but that text confirms part of my
original text

Regards Peter Neubert

-----------------------------------------

To understand the CA-1's unique features, you need to know a bit about how
carbon dioxide analyzers work.
Start geekspeak. Carbon dioxide is a big gas molecule reminiscent of Mickey
Mouse's head, with a central carbon to which is attached two oxygens at the
ends of springy double bonds. Shake it at the right frequency and it
resonates. The "right frequency" is in the infrared at a wavelength of 4.26
microns. Shine light at this wavelength through a sample cell and then blow
carbon dioxide through it. The intensity of 4.265 infrared light transmitted
through the cell will drop because it is absorbed and re-emitted at longer
wavelengths (this is why carbon dioxide contributes to the greenhouse
effect). Now, detecting infrared light is non-trivial because at room
temperature everything glows in the infrared including the sample cell, the
detector's housing and the detector itself. The infrared source must
therefore be modulated to distinguish it from the background. The detector
can be made to pay attention to the modulated signal alone and, with the
help of a lot of electronic processing, give information on carbon dioxide
concentration. In most carbon dioxide analyzers this infrared modulation is
achieved by a chopper - a rotating disk with cut-outs. It mechanically
interrupts the infrared beam at a known rate. The disk's motors consume
power, are unreliable and are the primary cause of failures in carbon
dioxide analyzers. End of geekspeak.
The Sable Systems CA-1 is an infrared-based carbon dioxide analyzer that has
no moving parts. We have completely eliminated the mechanical chopper by
directly modulating the infrared light source itself. This greatly improves
the CA-1's ruggedness and reliability, and simultaneously reduces its power
consumption still further because no motor is required and the infrared
source is only "on" for half of the time!

1998\03\26@025834 by Ray Gardiner

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>>
>>   Forget LEDs.  They are not available in the wavelengths that are
>>   absorbed by CO2.

>Peter Neubert <RemoveMEneubertKILLspamspamBOW.INTNET.MU> wrote:
>Well this is where you are wrong - as I said i did this once as a project at
>Loughborough University - and they are available

I researched this a year or so back, could not find a supplier of
IR leds for 4.2 micron. Yes they exist in R&D labs but I could
not find a commercial supplier. Where did you get them?

Ray Gardiner (DSP Systems) raySTOPspamspamspam_OUTdsp-systems.com http://www.dsp-systems.com
private email to:- spamBeGoneraySTOPspamspamEraseMEnetspace.net.au

1998\03\27@030612 by Peter Neubert

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Hi Bob and Ray

I just found the name of the company who suplied the diode and receiver. Its
called

Laser Monitoring Systems Ltd
United Kingdom

I dont have an address for them, I tried to look on the web, but not with
much luck - I think the are situated somewhere in mid-england so it should
be possible to find an address somewhere. Also they seems to be owned by
another uk company called Neutronics Ltd - maybe someone her knows more ?

regards

Peter Neubert

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