Pool Arduino controller to read pH, ORP and temperature

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Teapot
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby Teapot » Mon 15 Jan, 2018 10:22

Hi Paul, Your pool tech is just regurgitating what he learnt in pool school and most all books on the subject. Sadly these are all out of date. I even questioned two chemists who stated "your pH will drop off a cliff" Oh how is that? I asked. To have the pH drop off a cliff implies that a chain reaction would take place, would it I asked. They said no. For each measured amount of pH- the pH falls, without a big buffer (Alkalinity) it falls easier (cheaper to) and doesn't try to fight it's way back up. Bicarbonate of soda dissolved in water has a pH of about 8.1 to high for our pools. The stronger that 8.1 buffer is the harder it is to move and the easier it is to rise back up again. NOTE this is for liner and plastic/ fiberglass only and not for concrete! In case others read this.

Back on track, what level is your CYA stabiliser? this can easily wind down the REDOX figure.


paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Tue 16 Jan, 2018 05:13

ok did a heap of troubleshooting and found two issues, the 5v reference point i was using was wrong so the scale was way out and secondly the 5v PoE adapter i was using didnt have enough juice to run the temp sensor, ORP sensor and PH sensor so direct 5v USB and it works first shot.

i now get Ph of around 7.6, ORP of around 195mv and Temp of 25deg (c).

I now need to watch a few days of ORP and see what the data looks like and compare my other readings such as CYA and double check alkalinity but its looking promising, still a long way from ideal 600+mv for ORP.
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Fri 19 Jan, 2018 04:08

check out the logged ORP data, i am certain the sensor is damaged, $190 AUD for a new one :(

drraw.cgi.png
Teapot
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby Teapot » Fri 19 Jan, 2018 16:21

Hi Paul, You should be able to check the voltage off the back of the probe if they supply any data with it?
What is your CYA level?
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Sat 20 Jan, 2018 06:16

im certain the sensor is dead so ive asked the manufacturer for a replacement. the CYA levels were low and i added some stabiliser and brought the CYA levels upto around 50ppm. all the other chemicals look about right and at reasonable levels.
Teapot
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby Teapot » Sat 20 Jan, 2018 07:04

Ah, it's much easier to get things set up without the interference of CYA. If your gut feeling is the sensor, then you are most probably correct. I and others bought some of the cheapo's from Ebay which do work after a fashion but soon go completely off. I think they are meant for non chlorinated water maybe fish aquariums.
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Sat 20 Jan, 2018 19:58

yeah ill go for a replacement sensor, i had it working at home when i first got the sensor as i remember testing the code etc so yeah its damaged i would say.
the sensor is $190 AUD as its rated to ~100psi and industrial rated hence the added cost. their lab sensor is about $70 AUD but I figure im going to get a few years out of this sensor so may as well do it properly
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Wed 24 Jan, 2018 05:47

replacement ORP sensor on the way, should have it next week
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Thu 01 Feb, 2018 05:03

new ORP sesnsor arrived and all good, installed and working, pool water is 680mv at first sample
will get a weeks worth of data plot it up
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Thu 01 Feb, 2018 05:53

some initial data from pH and temperature

you can see our solar heating works wonders when the sun is heat, no problems running it around 28deg and maintaining that level. perfect for all day swimming with kids
temperature.png


we had an awful amount of rain on the 28th of JAN and it's skewed out the pH a bit
you can also see the daily effects of the salt water chlorinator slowly increasiong the pH day by day
PH.png


the reason for the pH staircase chart is because i cant sample pH while the pump is running at it skews the data it captures. the vendor reports pH and ORP should not be sampled while pumps are running. so my pump runs from 10am to 4pm so i sample pH for a window of 1 hour so thats why it looks like a staircase. this is fine for my appication as im more interested in the weekly trend as opposed to the daily value
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Thu 01 Feb, 2018 05:59

i have the opposite problem for the water temp sensor, i can only sample that reliably when the pump is running otherwise because of where the sensor is, it gets skewed by the air temp and temp of the water in the pipework, no where near the pool. so i made some code changes to;

plot temperature during pump run cycle - 10am to 4pm
plot pH 1 hour after pump stops - 4pm to 5pm
plot ORP at 11pm at night after 5 minute pump run to get fresh pool water from pool
Teapot
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby Teapot » Thu 01 Feb, 2018 11:50

Good stuff Paul, nice to see the ORP up near where it should be. That pH spike at 7.95 ish. If you bring down your alkalinity closer to 40-50 buy adding acid and then aerating to raise the ph back up and repeating until you have a lower alk figure you won't spike so easily. We don't need that much alkalinity, the pool water is still super saturated at 40ppm with bicarbonates at least 7x more in the water than the air but it will reduce the speed of the rise.
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Tue 06 Feb, 2018 04:00

some initial ORP data
i had a look at the commerical PH and ORP sensor for my chlorinator is about $1000 AUD and the sensors and arduino i got cost me about $400 and i dont have to worry about the system making the pump run flat out if it cant get a magical ORP reading so i much prefer this way.
paulr33
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby paulr33 » Tue 06 Feb, 2018 04:03

ORP
ORP.png
Teapot
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Re: Pool Arduino controller to read pH, ORP and temperature

Postby Teapot » Tue 06 Feb, 2018 04:49

That's looking better Paul, later on when it settles in I would like to know how much the strong sun has an effect on the ORP. Can you link the pump Doser up to see how often it runs?

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