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Using Arduino => Project Guidance => Topic started by: tsinghrumble on Feb 08, 2013, 06:24 am

Title: Pool Chemical Measurements
Post by: tsinghrumble on Feb 08, 2013, 06:24 am
My first post, go easy. I have a couple of arduino UNO boards and looking for something to monitor the chemical levels in my pool.
I want to do it using least amount of power, ie low power mode and I am having a pretty hard time finding probes or sensors.

I want to have a floating gadget in the pool; on its bottom-side would be multiple electrode/probes that measure different chemical levels. So the probes I am looking for would have to last a looooong time submerged in later, and live through hot and cold days through and through.

I imagine many pool owners here would be interested in having this gadget?

These are the sensors/probes I had in mind:
temperature - not worried should be able to find easily
ph level
free chlorine
bromine (for salt water pool)

would be cool if I could find these:
TDS (total dissoved solids)
Salt
Alkalinity
Cyanuric Acid

Ideas on sourcing these sensors? Anyone interested in a similar project would be great!

T.
Title: Re: Pool Chemical Measurements
Post by: michinyon on Feb 08, 2013, 09:37 am
I don't think there are "probes" to measure all of those things.

Apart from temperature,  the main thing you can measure in water,  is electrical
conductivity.   For specific applications,  you can draw conclusions from the measured
electrical conductivity based on known relationships between conductivity and concentration
of anions and cations in the water.   But you cannot easily determine which anions and
cations.

You can also measure pH,   which has some complications and requires calibration.

To detect other things,  you are usually looking at some kind of characteristic chemical
reaction  ( such as silver with chloride ions ),   which is difficult to do with a "probe".
Title: Re: Pool Chemical Measurements
Post by: nickgammon on Feb 08, 2013, 09:51 am
I've got a pool, but honestly, some of those measurements are likely to involve sensors costing thousands of dollars.

I would be most happy to be proved wrong. :)

A quick search reveals a number of web sites that supply sensors such as Cynanuric Acid sensors. Rather alarmingly, I haven't found a price quoted. I'm reminded of the quote: "if you have to ask how much it is, you can't afford it" which is code for "it's very expensive".
Title: Re: Pool Chemical Measurements
Post by: rthorntn on Feb 10, 2013, 06:36 am
Spooky, I just became the owner of a pool and was thinking along the same lines.

Floating measurement device
Solar powered with battery and charging circuit
Arduino
433Mhz Wireless

Initially I think these functions are important:
Ph sensor
Temp sensor

These would be cool:
A way to detect the water level - maybe the anchor being permanently on the bottom could have a REALLY accurate depth sensor or maybe a couple of magnets attached to the side of the pool and the floating lab can work out the level using a magnetic sensor?
Chlorine level - these sensors appear to be expensive, so probably too hard?
A way to detect the force of water coming out of the main pump outlet (to tell you the skimmer is blocked, the sand filter needs a backwash or the pump has issues) - the floating lab could be anchored next to the outlet and there could be a paddle that is moved by the water?

I am keen to get something happening here, thoughts?

Thanks.

Richard
Title: Re: Pool Chemical Measurements
Post by: zoomkat on Feb 10, 2013, 08:54 am
Quote
...and I am having a pretty hard time finding probes or sensors.


That is natures warning sign that they don't exist at prices that adverage people can afford.
Title: Re: Pool Chemical Measurements
Post by: lax123 on Feb 10, 2013, 10:04 am
I hope i get this right:
I dont think pH sensors are usually made for permanently exposing them to the substance u want to measure, as the tip usually has to get put a solution of KCl, also measurement isnt like just reading some stuff with analog in , you also need measurement bridges (hope thats the english term) and to amplify, as they have usually just changes in milivolts, and as it has been said continious calibration is an issue. And thats only pH...
Title: Re: Pool Chemical Measurements
Post by: robtillaart on Feb 10, 2013, 11:34 am
Quote
I dont think pH sensors are usually made for permanently exposing them to the substance u want to measure,

So the solution might be a PH robot that takes a water sample every hour and post it over wifi?
Title: Re: Pool Chemical Measurements
Post by: lax123 on Feb 10, 2013, 11:56 am
check this
http://www.phidgets.com/products.php?product_id=3550
http://www.phidgets.com/products.php?product_id=1130
http://www.ebay.com.au/itm/ws/eBayISAPI.dll?ViewItem&item=190542589314&ssPageName=STRK:MEWAX:IT