Pi-casso : an automatic alkalinity tester

[SDchris]

Have been busy with work. Hopefully in about 4-5 weeks will get some time.
Changed the stepper motor drivers to TMC5160-bob. These make driving the stepper motors really easy using python.
Currently using this code to drive them: python TMC5160 stepper driver
Originally bought the TMC5160 step sticks from Bigtreetech. After weeks of messing around, realise the motion controller is not available with these. That was the most important part of what I wanted.

Currently using the Atlas pH interface, Not a big fan of it. So staring to write a python module for the Reef-Pi pH probe interface.

Once finished the steppers and pH test unit will be separate pieces, similar to the Pac-sun KH lab.

Hopefully the changes will make the software much less convoluted, and easy for anyone to make changes.

Cheers

Chris

 

[SDchris]

I also have atlas pH probes (9 of them). They’re not bad for the price, but they’re not good either (+-0.2 pH reading error is not unexpected from them). Even at calibration you can wittness how it never really stabilises. I also have a GHL probe which is much more reliable, and is a lot more closer to Hach-Lange grade pH probes. Maybe the Atlas probe exchanges ions with the calib sol/sample/HCl & that’s the reason for the deviting readings. You could try and flush /store the probe with KCl after the measurements.

Cheers. Yes that sounds familiar with the Atlas probes
Have now bought a GHL probe, will try it out soon.
WIll try and keep the test cup and probe out of light first and see how that goes first. The KCl is a nice idea, just not really practical.

 

[peterj66]

Very interesting project. Ordered pumps from Kamoer a few weeks ago for exactly this kind of project. I was hoping to get started next week but due to the Corona virus all shipping between China and Sweden has been suspended so i guess it will have to wait. I was thinking of going for a combo of arduino and raspberry and let the arduino handle pump control, but I realize that might be overkill. How do you handle exact timing for the dosing pumps from raspberry?

 

[WallyB]

Cool. Stumbled up this thread since it was on the R2R home page listing.

Didn't know someone else was also making an Auto Alk Monitor.

Going to follow to see how your project evolves.

I used the exact cheaper DC motor for sampling, etc

Hat's off for the very ambitious project to do the Probe method.

Your probe enclosure is sweet!! (Wish I had the time to get into 3d printing)

 

[WallyB]

Very interesting project. Ordered pumps from Kamoer a few weeks ago for exactly this kind of project. I was hoping to get started next week but due to the Corona virus all shipping between China and Sweden has been suspended so i guess it will have to wait. I was thinking of going for a combo of arduino and raspberry and let the arduino handle pump control, but I realize that might be overkill. How do you handle exact timing for the dosing pumps from raspberry?

Actually I learned that's the best way (PI / Ardiuno), Instantaneous speed of the Ardiuno, but the Smarts, OS/Languages/libraries, Storage and Networking/Web Interface, etc, etc of the Raspberry. They key was designing a reliable communication protocol (PI<->Ardiuno<->Pi) and then a set of simple commands, functions and sequences.

With the Ardiuno Speed I use the Exact Same Kamoer DC pumps and can dose 1/10 of a drop. 1 ml or 1/2ml accurately is Super Easy. No need for the more expensive stepper versions.

 

[peterj66]

Cool. Stumbled up this thread since it was on the R2R home page listing.

Didn't know someone else was also making an Auto Alk Monitor.

Going to follow to see how your project evolves.

I used the exact cheaper DC motor for sampling, etc

Hat's off for the very ambitious project to do the Probe method.

Your probe enclosure is sweet!! (Wish I had the time to get into 3d printing)

I too decided to try using only dc motors. If they ever arrive that is . The goal of the project is to avoid spikes in alkalinity that I've had to deal with twice already so the accuracy is not superimportant as long as it is fairly consistent.

 

[WallyB]

I too decided to try using only dc motors. If they ever arrive that is . The goal of the project is to avoid spikes in alkalinity that I've had to deal with twice already so the accuracy is not superimportant as long as it is fairly consistent.

I totally agree with you 100%.
Consistency is key. Even if the test result value is off by whatever we want our Reef Tank ALK stable and a consistent measurement will achieve that. Your offset can be calibrated by computing a mathematical offset adjustment.

 

[SDchris]

How do you handle exact timing for the dosing pumps from raspberry?

Wave chains (python)
See here for an example script:
pigpio wave chains
And this video for an explanation: goto 23:00.
Raspberry Pi Stepper Motor Tutorial

The TMC5160-bob I'm now testing has an onboard controller (motion control). So all you need to do is send it the number of steps you want to turn, that's it.

 

[SDchris]

Hat's off for the very ambitious project to do the Probe method.

It turns out it's not really all that hard, the part that does the titration and calculation.. The time consuming part is all the associated stuff.
I love your project in that it's more unique.

 

[WallyB]

It turns out it's not really all that hard, the part that does the titration and calculation.. The time consuming part is all the associated stuff.
I love your project in that it's more unique.

So wondering, how are you going to handle when the PH probe starts drifting? (This is not about accuracy, this is about consistency)

I guess a temp/ph re-calibration will put things back on track....Just like any PH probe. Correct?
Or will you handle some software calibration and adjust any drifts (with some kind of Reference Solution) PERIODICALLY.
Some logic/algorithm/calculation to pick up a more significant change in results (ie bad tests)? (which is what I eventually plan on doing on my Alk Monitor)

Maybe the drift will be slow (and meaningless on Tank Stability). I don't know how PH probes age.

Too soon to say till you get there?

I would be cautious and learn/prepare how a PH probe acts at end of life.

 

[SDchris]

So wondering, how are you going to handle when the PH probe starts drifting? (This is not about accuracy, this is about consistency)

I guess a temp/ph re-calibration will put things back on track....Just like any PH probe. Correct?

Yes, 4-6 weekly clean re-calibrate.

Or will you handle some software calibration and adjust any drifts (with some kind of Reference Solution) PERIODICALLY

Probe condition can be checked in software a couple ways if needed. I'm not sure how much I will rely that ATM.
Using a test kit to manually correct any offset is an easy way.

Maybe the drift will be slow (and meaningless on Tank Stability). I don't know how PH probes age.
Too soon to say till you get there?

Yes and No. In my case yes not enough data. In general I know of other sps dominated tanks that have been using the same method and probes haven't been clean or calibrated in > 12months.

 

[dopey]

Stumbled upon this thread when trying to understand how complex automating alk testing is.

Have to say really impressive work sir! Love the grafana backend as well. I'm over here just doing some seneye readings and voice commands for manual testing into grafana, and you're fully automating alk testing. Love it!

Are you still running this? Still happy with it?

 

[BCI Can Do Better]

As quadriplegic with a 7 month old nano reef I've become kind of envious of everyone able to put together all of this automation. I was super excited when I found out the Trident was a thing that exists, but quickly had the realization that I would never be able to afford a system like that. If I were ever lucky enough to actually set up a larger tank I would want everything possible to be automated and monitored. There would be too much invested in it to let some things wait until I had a caregiver around to to do/check it for me, and hope it's done consistently between people. So it's nice to know maybe some good DIY options might be available for me in the future. I wish everyone good luck on their projects.

 

[MaddyP]

Following!

 

[SDchris]

The controller has taken a back seat till I finish building the display tank.
Have updated a couple things.
Made a carrier board for the electronics to clean up the birds nest of wires:
From this:

To this:

Also the the dosing pump / controller is built into the cabinet:

Cheers

Chris

 

[Dr. Dendrostein]

The controller has taken a back seat till I finish building the display tank.
Have updated a couple things.
Made a carrier board for the electronics to clean up the birds nest of wires:
From this:

To this:

Also the the dosing pump / controller is build into the cabinet:

Cheers

Chris

Thanks for sharing, also following

 

[t951]

I am interested in this....when you are done, will you create a BOM and creation guide?

 

[SDchris]

I am interested in this....when you are done, will you create a BOM and creation guide?

Sure. It's almost done. But the software needs a whole lot of tiding up. That may take a long time before that happens.

 

[Kerinin]

This is awesome! Where did you source the stepper motors and controllers?

 

[t951]

Sure. It's almost done. But the software needs a whole lot of tiding up. That may take a long time before that happens.

That's OK, I am TERRIBLE with HW....by the time I get it connected, you will probably be on Rev 4. and designed a solution for SpaceX for analysis on the ISS!
Great work, the talent at R2R is mind boggling!
t.