DIY Alkalinity Monitor

[Borat]

Hello folks from US&A. Warm hello from a friendly nation of Kazakistan!

Please check out my video for a DIY Alkalinity monitor that I built myself!





Cheers,

Borat.

 

[Borat]

The complete build thread is here:

Project AlKx : DIY Alkalinity Monitor + DIY Magnetic Stirrer

Hello fellow reefers.. Following a number of successful projects this year: - DIY light bar (https://www.ultimatereef.net/threads/diy-light-bar-100w-100cm-3-channels-pwm-dimming-temperature-control-active-cooling.890640/) - Calcium reactor...

ultimatereef.net

 

[Ranjib]

Welcome to reef2reef.
very nice .
I briefly browsed through that thread. I'll need some time to digest it . It will be awesome if you can summarize the build process (BOM and build guide), it will help anyone interested in building it

 

[KonradTO]

Scientist ingegnous man from Kazakistan made a very niice project.
Following up closely both threads!
I will add my version next year. My plan was to build an all-testing device using both pH probe and color recognition with everything rotating around a central circular column.
We'll see, time is hard to find

 

[G Santana]

Very very cool.
Hats off to you!!!

 

[Borat]

I am pretty much following @Randy Holmes-Farley DIY Alkalinity test recipe and the device simply automates the process. All commercially made alkalinity monitors are made in the same way:

- a set of motors that act as dosing pumps and are able to measure the amount dosed. Typically there are 3 motors: (#1) for adding tank water (#2) for removing tank water and (#3) for adding titration acid. These motors need to be stepper motors - in order to exactly measure the amounts of liquid added (although the motor for removing tank water can be a non-stepper motor).
- a reaction chamber with a PH probe
- a magnetic stirrer situated underneath the reaction chamber
- electronics componens: monitor controller (Arduino Nano), a PH board (DF Robot SEN0161 kit), 5v relay (for switching the stirrer), stepper motor drivers (TMC2209/one per motor)
- additional cooling fan as stepper motor drivers and stepper motors themselves generate significant heat

For every test the monitor performs the following steps:

- remove existing water (100ml) from reaction chamber (it’s kept there in order for PH probe to be continuously submerged)
- add small amount of tank water (20ml) – this is in order to purge water in tubing connecting the tank to the reaction chamber
- remove added small amount of tank water (20ml)
- add tank water to be used for test (100ml)
- start magnetic stirrer
- start adding 0.1N acid (hydrochloric acid 10% strength) in small amounts (10% diluted hydrochloric acid) and measure PH at each step
- when PH reaches an endpoint (just below PH 4.4) stop adding acid
- based on the total amount of acid used to reach the end point, alkalinity (DKH) can be calculated as acid_vol_ml*sample_water_ml/280
- remove sample water (it will have 0 DKH)
- add 100ml of tank water (again, in order for PH probe to be continuously submerged)

Used water is discharged back into tank - this has miniscule impact on tank DKH and is completely safe.

 

[Borat]

Some extra details are:
- all parts are made by hand, no laser cutting/pre-ordering of parts (i.e. by cutting the acrylic using simple tools such as handsaw)
- 5mm acrylic used throughout (Perspex), where 20mm acrylic was required for dosing head components - this was made by gluing 4 pieces of 5mm acrylic together

 

[Borat]

The greatest challenge for me was to build a monitor without having any prior knowledge about it or ever seeing the commercially made alternative..

So the thread should be a useful guide for others to follow.. Should you have any specific questons - feel free to reach out!

 

[KonradTO]

It's incredible you hand-cut all the parts! I had a look in the original forum thread and they look very accurately cut. May I ask what range of accuracy the peristaltic pumps need to have for the tank water intake and acidic solution dosing? What's the final KH accuracy of the device compared to color shifting solution-based tests?

 

[Borat]

It's incredible you hand-cut all the parts! I had a look in the original forum thread and they look very accurately cut. May I ask what range of accuracy the peristaltic pumps need to have for the tank water intake and acidic solution dosing? What's the final KH accuracy of the device compared to color shifting solution-based tests?

Some fellow reefers here in the UK made their own versions of these devices (I think there are only 2, me being the 3rd - in the whole of UK!). Unlike me they either bought dosing heads or 3D printed them.

As my dosing heads are hand-made, they can be made to squeeze santoprene tubing hard enough - so that once the pump is calibrated, it's 100% accurate (seriously - you can make it as accurate is you want to). Think of pump accuracy as within 1% max - so DKH 9.1 could be DKH 9.11 or DKH 9.09 (that's nothing really!).

The main weakness to accuracy (in my opinion) comes via PH probe and PH board. For the PH development board - I use a relatively cheat DF Robot v1 PH board (this is not as cheap as some Chinese unbranded imitations), for higher accuracy I would recommend Atlas Scientific PH board instead (I have heard about them but never used before). For the PH probe itself I use Extech Instriuments PH probe - it's a decent quality probe that's probably adequate for this task.

But even with my relatively cheap PH board - I would (probably in 4 out of 5 tests) get exactly the same DKH (to 1 decimal place) if I rerun the test... So the overall accuracy is better than 0.1 DKH..

As compared to other test kits - I am still digesting it.. My monitor is giving the (broadly) same (+/- 0.2DKH) DKH as Salifert test (I always used Salifert), but I still have my open questions after I read an excellent article on this site:

Alkalinity titration endpoint pH & Salifert endpoint color

TL;DR: The endpoint pH is 4.41, and the endpoint color is that "lavender" color I've been telling people about. Over the years, there have been many threads on R2R and other forums debating a couple of basic details relevant to testing for alkalinity in reef aquaria. One of the most...

www.reef2reef.com

 

[Borat]

Prior to building this monitor I built a DIY calcium reactor (and DIY peristalstic pump for it)..

Project CaRx: DIY Calcium Reactor + DIY Controller + DIY Peristaltic Pump + DIY ALK Monitor

Hey folkes, 2 large DIY projects completed this year and now I am sitting idle.. What should I do next? The target for my tank is to slowly grow into an SPS dominant system. I already have 3 palm sized plating easy-going monties and have to dose about 100ml of alkainity solution daily (100mg...

www.ultimatereef.net

This is where I mastered the technique of building dosing pumps. My main source of knowledge/aspiration (although with limited amount of details) for building my first peristaltic pump was actually here:

My Version of a DIY paristaltic pump

As I get settled in with my new tank, aspirations of having a full blown SPS dominant tank requires me to have stable alkalinity, which means I will need a calcium reactor at some point in the future. From talking with friends and reading on line, I discovered that using a pump and needle valve...

www.reef2reef.com

 

[KonradTO]

Prior to building this monitor I built a DIY calcium reactor (and DIY peristalstic pump for it)..

Project CaRx: DIY Calcium Reactor + DIY Controller + DIY Peristaltic Pump + DIY ALK Monitor

Hey folkes, 2 large DIY projects completed this year and now I am sitting idle.. What should I do next? The target for my tank is to slowly grow into an SPS dominant system. I already have 3 palm sized plating easy-going monties and have to dose about 100ml of alkainity solution daily (100mg...

www.ultimatereef.net

This is where I mastered the technique of building dosing pumps. My main source of knowledge/aspiration (although with limited amount of details) for building my first peristaltic pump was actually here:

My Version of a DIY paristaltic pump

As I get settled in with my new tank, aspirations of having a full blown SPS dominant tank requires me to have stable alkalinity, which means I will need a calcium reactor at some point in the future. From talking with friends and reading on line, I discovered that using a pump and needle valve...

www.reef2reef.com

Thanks for the link! I think I will get some (a lot) of ideas for my personal version of this device. I never thought of building my own pump! Basically the tighter you make the bearings around the tubes the more you get precise dosing (less liquid per each step pass through them) right?

 

[Daniel@R2R]

Very very cool!! Thanks for sharing with us!!

 

[Ranjib]

I am pretty much following @Randy Holmes-Farley DIY Alkalinity test recipe and the device simply automates the process. All commercially made alkalinity monitors are made in the same way:

- a set of motors that act as dosing pumps and are able to measure the amount dosed. Typically there are 3 motors: (#1) for adding tank water (#2) for removing tank water and (#3) for adding titration acid. These motors need to be stepper motors - in order to exactly measure the amounts of liquid added (although the motor for removing tank water can be a non-stepper motor).
- a reaction chamber with a PH probe
- a magnetic stirrer situated underneath the reaction chamber
- electronics componens: monitor controller (Arduino Nano), a PH board (DF Robot SEN0161 kit), 5v relay (for switching the stirrer), stepper motor drivers (TMC2209/one per motor)
- additional cooling fan as stepper motor drivers and stepper motors themselves generate significant heat

For every test the monitor performs the following steps:

- remove existing water (100ml) from reaction chamber (it’s kept there in order for PH probe to be continuously submerged)
- add small amount of tank water (20ml) – this is in order to purge water in tubing connecting the tank to the reaction chamber
- remove added small amount of tank water (20ml)
- add tank water to be used for test (100ml)
- start magnetic stirrer
- start adding 0.1N acid (hydrochloric acid 10% strength) in small amounts (10% diluted hydrochloric acid) and measure PH at each step
- when PH reaches an endpoint (just below PH 4.4) stop adding acid
- based on the total amount of acid used to reach the end point, alkalinity (DKH) can be calculated as acid_vol_ml*sample_water_ml/280
- remove sample water (it will have 0 DKH)
- add 100ml of tank water (again, in order for PH probe to be continuously submerged)

Used water is discharged back into tank - this has miniscule impact on tank DKH and is completely safe.

Awesome. Thank you so much

 

[Borat]

Thanks for the link! I think I will get some (a lot) of ideas for my personal version of this device. I never thought of building my own pump! Basically the tighter you make the bearings around the tubes the more you get precise dosing (less liquid per each step pass through them) right?

Not quite. The accuracy of positioning of ball bearings (and their number) will determine how quiet your pump will be:
- if the ball bearings are slightly non-central, you will get the oscilating noise from the pivot going up and down
- if there is not enought rows of ball bearings (e.g. if you make the roller with only 4 rows of ball bearings), you will also end up with pivot assembly wobbling a bit
- larger number of rows of ball bearings obviously means less liquid pumped for each turn (which may be a problem if the pump is for calcium reactor and needs to pump, say 200ml / min) but higher volumetric precision

Think of a dosing head.. it needs to be built (to the last 0.25mm) precisely in such a way that it squeezes santoprene by precisely the required amount:
- If santoprene tubing is not squeezed enough, water may back-flow (caused by differential in water levels) or, if some air gets in the tubing, the pump may fail to work at all
- If santoprene tubing is squeezed too hard, the motor may not have enough power to turn the roller (squeezing it harder than required does NOT really change the amount of liquid pumped)..

Therefore ideally santoprene tubing needs to be squeezed by (exactly) a certain amount (and not greater than that).

With the pivot assembly (as I use, it's similar to Kamoer FX-STP pump) pivot manufacturing accuracy is much less important. Pivot arch just needs to have a slightly larger diameter than the roller (as measured to protruding ball bearings edges) - but it does not matter whether it will be 2mm larger or 4mm larger.. You can adjust the force with which pivot will squeeze the tubing using the adjustment screw.

 

[Borat]

The precision to dose small volumes (acid ) is achieved by using santoprene tubing with smaller diameter:
- for tank water addition/removal pump, it's 3.2 ID tubing (1ml ~ 1.5 turns of roller)
- for acid addition it's 1.6mm ID tubing (1ml ~ 4.5 turns of roller)

Obviously with Nema 17 stepper motor and TMC2209 driver I can turn the roller by 1/256 turn at a time, so 1ml is can split into 1152 increments (in reality the minimum acid increment I use is much larger and corresponds to 0.1DKH change. That's roughtly 0.035ml or 1/7 roller turn)..

 

[KonradTO]

The precision to dose small volumes (acid ) is achieved by using santoprene tubing with smaller diameter:
- for tank water addition/removal pump, it's 3.2 ID tubing (1ml ~ 1.5 turns of roller)
- for acid addition it's 1.6mm ID tubing (1ml ~ 4.5 turns of roller)

Obviously with Nema 17 stepper motor and TMC2209 driver I can turn the roller by 1/256 turn at a time, so 1ml is can split into 1152 increments (in reality the minimum acid increment I use is much larger and corresponds to 0.1DKH change. That's roughtly 0.035ml or 1/7 roller turn)..

OK now I got it. Thanks for the explanation!

 

[Borat]

Now the monitor is a complete hands-off device, I have scheduled 4 tests to be run daily:
- 9am (morning)
-12pm (noon)
-3pm (afternoon)
-3am (nighttime)

I am running a DIY calcium reactor (2 chambers, total media volume = 7L) with a DIY PH controller (2 PH probes) and a DIY peristaltic pump, this seem to achieve quite an impressive DKH stabillity (it's an SPS tank, although I would describe it as "SPS beginner").

Considering I am a complete newbie to the concept (calcium reactor) - it's not bad at all!

 

[Machpoint89]

What an awesome read and welcome to Reef2Reef. My hat off to you sir. Very fun to read the original build thread.

 

[Appoloreefer]

Hello folks from US&A. Warm hello from a friendly nation of Kazakistan!

Please check out my video for a DIY Alkalinity monitor that I built myself!





Cheers,

Borat.

There is no words so how do we know you built it? Welcome to the forum