Questions about building my own Chem controller and using Atlas Scientific sensors, including EZO-PRS

[psmith3]

@tagyoureit I have been successfully running NjsPC now for a few years now and have a simple setup connected to a Aquarite 940 salt generator and automating it in Home Assistant and just updated to 8.0.1. I have been studying the Chem controller documentation and think I am on the right track for adding a PH sensor, ORP sensor, EZO-PRS pressure sensor. Before I purchase the next pieces of equipment, I wanted to ask a few questions.

1. Have the Scientific Lab grade sensors gotten better than your early reports? They are on sale right now and so much cheaper than the Industrial probes. I could buy almost 4 of the PH lab-grade sensors for the price of the industrial, but I also know there is no temperature sensor embedded. I could get 2 lab-grade ORP sensors for the price of the industrial. I know they will not be on sales forever and also the shelf life does not justify buying extra lab-grade models now.
2. If I go with the Industrial PH sensor with built-in temperature, I need to add a EZO-RTD to the Whitebox T3, right?
3. Will the EZO-PRS Sensor work with the Whitebox T3 hat and be visible in REM? I also see this can substitute the need for a flow sensor? Is that substitution an easy configuration in REM?
4. I am not a fan of drilling and tapping the IPS Complete Flow Cell and was thinking about making my own with PVC and NPT T-joints? Could the PH & ORP sensors be installed in the main return lines with a couple of T-fittings with NPT ports after the filter? I don’t have a heater and just have a sand filter feeding my salt cell generator to my return line. Any issues or concern with not going with a purpose built flow cell?
5. I am thinking about not adding an acid tank at this time and manually add acid. Will the NjsPC tell me how much acid to add based on my pool size? Would this be a problem?
6. Do I need an another outside air temp probe? I have a Tempest Weather station providing air temp data to Home Assistant now, but not sure if I could populate the outside temp with data through home assistant using the integration or MQTT.
7. Is there any other chemistry I need to consider for a salt pool other than PH & ORP? Obviously I will be using my Aquarite 940 to generate chlorine rather than dosing it with a chlorine tank.

Attached are screenshots of the checkout cart at Atlas Scientific; one with industrial-grade sensors and required components; another with lab-grade components for comparison in price.

Thanks in advance.

Vs.

A little over $300 difference on price.

[rstrouse]

@tagyoureit might have different opinions but here are a few things to consider.

1. If you do decide to add an acid pump later you will need a 24vdc power supply. Adding a MEGA-BAS to your pi will provide the following items

• Provide power for the the pi
• Provide digital inputs for flow switch
• Provide temp probe inputs that will survive the sun and demanding environment on the pad. 10k temp probes are simply installed in the plumbing and can be sent to the pH circuit for temperature calibration. They also will show the pool and air temp for you. A 2 pack is less than $20.
• Allow for 0-10v inputs so you can use a much less expensive pressure transducer. <$20

2. If you do choose lab grade probes (even if you only do this initially) you can use the IPS flow cell without modification. This will also give you a very reliable flow switch for when you do decide to auto dose.
3. The Home Assistant integration will show you the current acid demand in mL.
4. Plumbing a flow cell is a relatively easy thing to do. You simply drill a couple of holes and insert a fitting. It also makes it very easy to ensure you have proper flow for the readings. If you do use the lab grade probes you will find that you do not need to modify the cell in any way. It will come with fittings that readily accept these probes.

All told if you are looking to budget you can get the cost down by using a pressure transducer and an ADC for temp probes or you can get a MEGA-BAS and hook up the temp probes directly. For a 2-pack these cost around $20 and this will give you both air and water temp.

[psmith3]

Thanks much @rstrouse! Funny, I actually meant to tag you in my question and not @tagyoureit 😂 Did that by mistake. Thanks much for the detailed explanations.

[tagyoureit]

Funny, I actually meant to tag you in my question and not @tagyoureit

Aww, now my feelings are hurt! 😢 But I concur with @rstrouse. He always gives good advice!

I would add to:

I am thinking about not adding an acid tank at this time and manually add acid. Will the NjsPC tell me how much acid to add based on my pool size? Would this be a problem?

The single best part of my entire setup is the automatic acid dosing. Not having to go out to the pool and fill/measure and have spikes in your pH either high/low has been the biggest game changer. njsPC will keep a steady 7.65 (or whatever setpoint you choose) and it will hardly ever fluctuate and you'll never need to think about manually adding acid to the pool again. We don't have a prompt to tell you exactly how much you need to add, but since we already do that calculation for the automatic dosing it wouldn't be too much of a leap to show it in the UI. Not having the automatic acid dosing is like ordering an ice cream sundae but not getting the whip cream with it. :)

[psmith3]

Well, you both have provided equally good advice and support for a while now! Thanks to both (@rstrouse and @tagyoureit) of you☺️

[jamestalmage]

I'm going to jump in here and add a few more questions:

@psmith3, you said:

Have the Scientific Lab grade sensors gotten better than your early reports?

Where are those early reports? I'm not seeing it on the Chem controller Wiki. Shelf life is obviously half, but so is the price... I will need to bring the sensors inside every winter anyways, so the longer shelf life isn't really saving me labor.

@tagyoureit @rstrouse

Have either of you considered the combined ORP / PH / Temp sensor? It is pre-terminated with SMA connectors, and it saves $20. Only downside I can see is that if one half fails (PH / ORP), you're now stuck paying to replace both... Is that likely? They both claim the same shelf life. One less probe to care for means a litttle less work for seasonal commissioning / decommissioning .

[davthomaspilot]

I don't have any experience with the Atlas Scientific probes.

I've gone through two sets (currently using the third set) of expensive Accutrol/Pentair probes. The third set is still working and they will be measuring along side the AS consumer grade probes.

All probes wear out--the solution inside them gets contaminated by the water they are sensing. Bigger volume means they can go longer before they get contaminated and inaccurate.

You can buy reconditioning kits, but I'm going to try buying cheap probes and treating them as consumable items.

It takes the same amount of time to replace them as it does to calibrate them, unless you've gone with the AS commercial grade probes. On those, you will have to add a connector.

Accutrol probes don't include a cable--they have a BNC connector, So, you reuse the cable with its connectors when you replace the probes.

Atlas Scientific consumer grade also have a cable and SMA connector. So, you don't have to bother with buying and crimping/soldering connectors when you change probes.

I know I'll have to keep replacing probes. It's just how often. It's really easy to change them, so it comes down to cost.

The jury's still out--I won't know until this time next year whether this is the better approach for me (versus commercial grade). If the consumer grade probes last a season, I think they are the way I want to go.

I'll add one other thing--

I'm really only interested in their accuracy in and around the set point. I don't care if the ph is 7.9 or 8.1--either way acid needs to be dosed.

On the ORP probe, I find out pretty quickly what ORP is required to keep algae from growing. I don't care if the probe thinks that 650 or 750 mv. Just used to decide when to dose, not to get an "accurate" reading.

[tagyoureit]

@tagyoureit Is the argument that the industrial might be more robust against freezing? Is the issue the tip, or the entire length of the probe? (keeping water running as freeze protection will only be effective for whatever portion of the probe is submerged).

No, all probes are subject to freezing. There is only a small portion of the tip that will be touching your pool water. The rest of the probe is exposed to the air/elements.

This makes me wonder about my intent to use the flow cell. Should I DIY inline it somewhere after the heater, so there is more flow and more heat? How fast is water flowing through those 3/8" flexible lines?

You should have your probes reading the pool water before it goes through any filter/heater, etc. My 3/8" lines come directly out of my pump and then the output side (I forget the fancy word for this atm) is after my heater/chlorinator. You want the reading to accurately reflect what is going on in your pool. The filter could potentially affect the pH/ORP if it is really dirty.

OR... There is a possibility of me poking the lines to/from the flow cell into my garage, and keeping the flow cell in there. The garage will be heated (not super warm, but above freezing), and insulated.

If it is close enough, sure. Somewhere @rstrouse has posted a picture where his flow cell is mounted on the back of his Intellicenter enclosure. The power supply generates enough heat to keep the probes from freezing when you put a heavy duty garbage bag over the entire enclosure. I did the same on my setup.

OR... Should I return my combined sensor (pay restocking), and just opt for the consumer grade sensors and replace them every year.

I will never go with the consumer grade probes again. I'm now a big fan of the industrial probes.

[subcritical71]

I've been very happy with the combined probe. I think the only downside would be if either pH or ORP independently seems to go wonky, but given the expected life, price/value ratio, and previous disappointment with the consumer grade probes* I took the plunge and have been very happy with it.

I purchased Dec 2021 and it's been solid. I haven't even recalibrated it although it should be done at least yearly.

• For me, the consumer grade probes seemed to work for 9-12 months and then exponentially degraded. I spent more hours than I can count trying to calibrate and re-calibrate the probes only to come to the conclusion that they need to be replaced (with the help of Atlas support). Adding in all those hours of frustration and the value of my time, it makes the industrial probe that much more attractive.

A key to making the probes last is making sure they don't freeze. Keeping them above freezing temps (if that's applicable in your area) makes all the difference in the world. I don't need to winterize where I am, but we do get freezing temps. The official diagnosis from one of the Atlas support folks was "the jelly leaked out of your probe" and was most likely due to exposure to harsh temperatures.

How do you feel about letting the probe see full flow of the pump? I was all set to setup a bypass loop and then came across some literature on the Atlas site which indicates flow is not a problem (unless it can break your fingers!). I'll do a bypass loop with no hesitation if the thought is not doing so would reduce probe life. Thanks.

[tagyoureit]

There are a few factors to consider... While full flow itself isn't necessarily an issue, bypasses are good for a few reasons:

1. Lower flow means less abrasion on the sensors. I would definitely not put the sensors in full flow before the filter. You don't want anything to ruin the surface of the bulbs that allow accurate measurements.
2. Bypasses can have shutoff valves. If you need to do any maintenance or remove the probes for the winter a bypass makes this easier.
3. You don't need very much flow at all for accurate measurements.
4. If you live in an area that experiences freezing temps, it will be harder to keep the probes from freezing. Many of us use the IPS flow cell and mount it on the back of the OCP where the power supply creates enough heat (with a garbage bag covering everything) to keep the probes safe in cold weather.
5. Flow cells let you see the water as it moves past the probes.

just my .02.

[subcritical71]

Thanks for that explanation. I felt that a bypass was probably the best way but needed that push to knock me out of my lazy way! I think I'll go with the bypass arrangement. That is an expensive probe and I don't want to be replacing it any time soon.

[johnny2678]

my 2c

I lack the tools, skill, and mental fortitude to make my own flow cell or do a 3/4" NPT tap in perfectly good (and $$$) IPS cell, so I just use the consumer probes. 😂

Have tried the lab probes as well and found that their lifespan was about the same as a consumer probe in my environment.

I calibrate every 6 months and replace ever 12-18 months. I can tell a calibration is needed when the manual taylor kit ph reading starts to diverge from the Atlas probe reading, using graphs like this:

I recently just calibrated since we are back in the pool again. Surprisingly the probes are still ok after 12 months but pretty sure this will be the last season before I order another pair. Ideal Acid/Base are in the low 80%s now.

I prob should have calibrated during the Winter months but I let the water get down to 60-65 degrees so I don't worry about the chemistry as much since we are not swimming.

[davthomaspilot]

Nice!

Do you try cleaning the probes with a toothbrush before calibrating?

[johnny2678]

I guess I should, but don't think I did this last time around.

[psmith3]

Ok, so if anyone is interested in some savings. Whiteboxlabs has a sale going on right now with a few components required for this setup. 30-50% off for the Whitebox T3 for Raspberry Pi, Atlas-Scientific Industrial ORP probe, I2C Toggler, and pH Calibration Set (6 pouches). Saved about $100 from ordering from Atlas Scientific directly. Shipping from Switzerland, so hopefully it will be here soon without duty tax.. Ordered the rest from Atlas Scientific directly just now...

[psmith3]

Is it normal for PH values to swing as much as 7.3 to 7.5 within several seconds? I am using the Industrial PH probe and just recalibrated last night after installing my new flow cell. How many seconds should I have the read interval for PH and ORP sensors set to in REM? I saw this swinging value when I first installed and have the Raspberry Pi powered by a PoE adapter. I tried a 3 amp power adapter to rule out any power issue and the readings still varied. Take a look at videos of the values swinging. Is this normal?

https://github.com/tagyoureit/nodejs-poolController/assets/14373163/216ddb81-c3b2-4650-971a-fa770c2ce57a
https://github.com/tagyoureit/nodejs-poolController/assets/14373163/9b5753dc-eacb-4b6d-aeca-bfc652836438
https://github.com/tagyoureit/nodejs-poolController/assets/14373163/77b49d05-8e05-4f41-9759-56437c9ed0f1

[johnny2678]

didn't watch all 3 but the video i did see you were dosing Cl as the pH values are changing. Assuming your dosing from a tank? What's the strength of the Cl?

Just took a look at my readings over the last 5 minutes and pH only changes within 0.01 - and that's on the consumer probe.

Absent any major chem dosing, pH should stay fairly pegged to your setpoint with minimal acid dosing if you've got your water chem dialed in right. Here's mine today floating back up to my 7.8 setpoint after adding a bag of salt yesterday, which cause the pH to dip.

And here's mine over the past year. Mostly at the setpoint with only anomalies being chem dosing (salt/CYA causes it to fall, Baking Soda causes it to rise), or a probe calibration event.

Curious if you pause Cl tank dosing if the pH values level out?

oh, and I'm using 10s probe reads.

Another thought, i don't use this but REM has the ability to smooth values over X # of readings which might help level you out if readings are erratic.

[psmith3]

I am dosing from my salt chlorinator and using an Aquarite 940. I have it set in REM to ORP enabled, Use Chlorinator, and Dose by Dynamic based on ORP setpoint. Do I have that wrong?

[johnny2678]

no no, I just wouldn't have expected an SWG to affect pH as much as Cl dosing but I only have experience with my pool. I do know that dynamic dosing runs the SWG at 100% so depending on your setup I guess that could temporarily affect pH as well.

Is your pool return (newly chlorinated water) near your drain/skimmer line?

[psmith3]

No, the return is 6' from a skimmer and about 12 feet from the bottom drain. I noticed during calibration the settings swung a few 100ths of a point, but not anything like what I see with the pool running. Current in the flow cell is slow too.

[psmith3]

At some point today, the message went away. I’ll keep monitoring it to see if it happens again. Thanks, Parker On May 21, 2023, at 3:08 PM, rstrouse ***@***.***> wrote:  While that message is displaying, capture a replay and post it here. That message will appear when we haven't had a response from the chlorinator in a while. It could be that the 940 just doesn't talk back as often as we would like. The Pentair units are very chatty. — Reply to this email directly, view it on GitHub<#719 (reply in thread)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ADNVCK7QO5DJOS6H6QVDIZ3XHJY4XANCNFSM6AAAAAAW5VE7RU>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[rstrouse]

Bear in mind that message is not incorrect. If the cell stops responding and they often do (for instance when it is recalibrating its TDS levels) the message will appear.

[psmith3]

Ok. Good to know. Thanks. On May 22, 2023, at 11:27 AM, rstrouse ***@***.***> wrote:  Bear in mind that message is not incorrect. If the cell stops responding and they often do (for instance when it is recalibrating its TDS levels) the message will appear. — Reply to this email directly, view it on GitHub<#719 (reply in thread)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ADNVCK35BKR3ZNIKG55XXFDXHOHV7ANCNFSM6AAAAAAW5VE7RU>. You are receiving this because you were mentioned.Message ID: ***@***.***>

[kennybitte]

I'll just say the lab grade ORP probe from AS lasted a month for me. I have 2 EZO-PMP's both crapped out after switching them to I2c mode. They lasted about a week, so I soldered wires directly to the motor and run them with relays now. Then the tubing extender kept popping out of the pressure side of the pump spraying chlorine everywhere, which I assume is what killed my ORP sensor as it dropped to 100 mV then started reading negative mv amounts. I don't know how a splash of chlorine would cause an issue with the probes mounted in a flow cell, but alas I relocated the chlorine tank 10' away from the equipment pad.

I purchased a cheap ORP probe on Ali express, swapped it out and it works as a temp solution.. Still I reordered another Lab grade ORP probe from AS, if this one goes out (in less than a year) I'm not going to get probes from AS again.

my 2cents

[rstrouse]

I wondered about the EZO-PMP. I bought one then opted to go for the Pentair tank with the integrated Stenner. I still have the EZO-PMP so I can support the integration but when compared with the components of the Stenner it was obvious in the durability of the parts.

[psmith3]

I bought the EZO-PMP a couple of weeks ago, and it works well. I did upgrade the hose and bought the version that supports acid. I removed the cassette, removed the stubby hose, and installed the new single length of hose between my homemade 5-gallon acid tank directly to the plumbing. The thing I liked about the pump is that it did not need a check valve to prevent water from the pressure side from entering. The design of the peristaltic pump has pressure on the line and blocks the flow until the paddles turn the line. So far, so good.

[rstrouse]

I saw you were getting yours at Home Depot, and so did I. This one specifically: https://www.homedepot.com/p/HDX-1-Gal-Muriatic-Acid-Balancer-2-Pack-10031HDX/206809317

That is 31.45 (full strength) MA. The 14.5% comes in a white box.

[rstrouse]

Here you go
https://www.homedepot.com/p/HDX-1-Gal-Swimming-Pool-Muriatic-Acid-Balancer-2-Pack-10014HDX/206809290

[psmith3]

Now I see where you see the percentage! Thanks for the clarification!

[rstrouse]

Normally you would buy that if you were about to stain or coat concrete.

[johnny2678]

That is 31.45 (full strength) MA.

This is what I buy and dilute 1:1

[davthomaspilot]

I used to buy cases at Lowes'--the one with the green label that had less fumes (when it was available).

This spring, I switched to getting it from Amazon--just for the convenience of not having to drive to Lowe's and lug a case home:

https://www.amazon.com/Acid-Blue-Muriatic-CPDI-Swimming/dp/B0B77R3LGB/ref=sxts_rp_s_a_1_0?content-id=amzn1.sym.3432eb1a-1558-4445-9430-9bb3e7f7b9b7%3Aamzn1.sym.3432eb1a-1558-4445-9430-9bb3e7f7b9b7&crid=FWPHUWPFNYJ&cv_ct_cx=muriatic%2Bacid%2Bfor%2Bswimming%2Bpools&keywords=muriatic%2Bacid%2Bfor%2Bswimming%2Bpools&pd_rd_i=B0B77R3LGB&pd_rd_r=93f93e97-085c-42df-bb35-6f9267c54b3b&pd_rd_w=9cQ6k&pd_rd_wg=yy8Gd&pf_rd_p=3432eb1a-1558-4445-9430-9bb3e7f7b9b7&pf_rd_r=FM9A197RJZNG12G72NFX&qid=1686140003&sbo=RZvfv%2F%2FHxDF%2BO5021pAnSA%3D%3D&sprefix=muria%2Caps%2C81&sr=1-1-5985efba-8948-4f09-9122-d605505c9d1e&th=1

31.x %

I've never diluted the acid. Seven years later, no issues, except I do have to change check valves and pump tubes about yearly.

[rstrouse]

I am not sure there is any noticeable effect on plastic or the santopreme tube. These parts are inert and pretty much immune to acid which is why they are used to store, produce, and transport it. The pump tubes flatten out as the rollers push against them and this is the wear item. Its like a permanent smirk because its face got stuck that way. The composition of the tube doesn't appear to change though it just doesn't expand to draw the acid as much.

Where the problems come in are when there is exposure to other parts that are not inert. It will cause corrosion and degradation. If the pump motor is exposed to the fumes or splashing when filling then it will corrode.

[davthomaspilot]

Have you checked your Total Alkalinity lately?

When that gets low, it doesn't take much to swing PH wildly.

[psmith3]

Not in a week. It was low at 37 ppm last I checked. Maybe I need to get that one up and see if the PH gets stable. I’m still trying to get my initial balance.

[rstrouse]

pH changes happen very quickly. For instance, I have a large number of solar panels and if the pH of the water is different it will immediately change the pH when the solar kicks in. If you decide to add some chlorine you will also see this happen rapidly.

It is funny but the folks at TFP claim this has no effect on pH but that isn't the entire story. It can take several hours after adding sodium hypochlorite for the pH to stabilize back to where it started.

ORP changes however are very different. What your probe is looking at is the reduction potential. In many ways this is more indicative of how much sanitation can take place. Reading the FC simply tells you how much free chlorine there is. There is a corollary and it is easier to take an instantaneous measure of FC to get an idea of the water sanitation.

It will swing in a pattern all day as the oxidation chemistry of the water changes. The higher the mV reading, the more likely that oxidation of a baddie will occur rapidly. You can have a high FC and said baddie can hang out for a while until it oxidizes with a low ORP. Conversely, you have have a low FC and still beat down the baddies. I have witnessed a change by simply having a pair of ducks soil the pool. All in a 15 minute period.

[psmith3]

Thanks for the explanation. Learning constantly!

[rstrouse]

Did you set a mix time? The logs do not show a volume dosed above 100.

[rstrouse]

You should also set a max daily volume.

[psmith3]

I am still having a major challenge with my pH and ORP levels swinging up and down, constantly. I have been tinkering with my setup all day and have not narrowed anything down. I've made sure my EZO boards are isolated properly on my Whitehat T3 and made sure the boards are PH on port 1, ORP on port 2, RTD on port 3 and no difference. I am using a Raspberry Pi 3b. Should I be using a Pi 4? Have not tried swapping to that yet. Also, what about the flow rate in my flow cell? I have the in and out valves positioned where just a little bit of water is trickling down the exit tube and still see my values swinging +/- .2 points every 2 seconds. The ORP has been swinging from 175 to 550 range for the past week. Could my new probes need cleaning with bleach or a toothbrush? I am stumped. Take a look at these levels swinging over a 7 day period. I do see some trending with the ORP levels and cannot determine what in my system would be interfering with the probes. I have my ORP setpoint at 750. How do I determine the correct level of that setpoint? When I tested my water at my pool store last Friday, my ORP was reading ~450, yet my chlorine was actually high as seen in the attached test sheet. My industrial probes are connected to the EZO boards with the wire to SMA adapters that have a male-to-male SMA connecting the adapter to the EZO. Should I soldier the leads to the adapter? to the adapters?Any suggestions?

[rstrouse]

That is a pretty large swing. What kind of connectors are you using? Did you crimp connectors on the end of the probes? I have seen this once before when the connector was dubious. My suspicion is your connectors.

As for flow, you really cannot get too much water flowing through the flow cell and as long as it is flowing you should be ok there as well. That wouldn't cause swings between the readings.

[psmith3]

I thought it was a big swing too. Last night, I changed my reading time to 2 seconds and changed the feed sampling to 30 so it would give me an average over 1 minute. That has helped cover it up... I am using the SMA to Screw terminal boards from Atlas.
https://atlas-scientific.com/connectors/sma-screw-terminal/
I did not buy any SMA connectors to crimp to yet.

[jamestalmage]

@johnny2678 @psmith3 Sorry to hijack this thread, but quick question.... Where is everyone getting the cool graphs?

[johnny2678]

Just set up the Influx integration and hook up Grafana!

[johnny2678]

I've been running this setup for years, even before @tagyoureit put influx integration into njsPC. So I have a bunch of non-standard schema dashboards mixed in with the njsPC. Would offer to share but it wouldn't port well due to my pre-nsjPC components.

[tagyoureit]

At the bottom of the Influx section are some starter dashboards from v1.8.