DIY Alkalinity Monitor
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I don't know what price point you are trying to hit, but there are often very good deals on syringe pumps on Ebay (for example https://www.ebay.com/itm/Lot-of-4-C...784343?hash=item41dcd47117:g:BgUAAOSwoBtW4Gwb ). These are much more accurate than peristaltic pumps and don't require much in the way of ongoing calibration. These are often used in laboratory precision dispensing systems...
rygh
Community Member
It seems like you could make a semi-precision syringe pump reasonably easy.
Two check valves, a syringe and a cheap linear actuator.
small linear actuators are < $20, and maybe < $5 on ebay.
Check valves and syringe are super cheap.
Accuracy can be increased by making syringe diameter small, but length large, and test sample large.
Two check valves, a syringe and a cheap linear actuator.
small linear actuators are < $20, and maybe < $5 on ebay.
Check valves and syringe are super cheap.
Accuracy can be increased by making syringe diameter small, but length large, and test sample large.
OP
OP
certain_code
Active Member
Wow, thank you all for the suggestions and advice. Love the community here.
Scanned over most of the posts and here are some thoughts based on those:
1. I have tried weighing the liquids as an alternative but found the scale to be a pain in the butt to accurately get a measurement. It might just have been the cheap load sensor I had but either way I just didn't like some of the challenges that were to be if I went that route.
2. I know there are better pumps out there and eventually I will add support for the better stepper based pumps for for now the goals are to hopefully eliminate the need for an accurate pump and also to keep the overall product small.
3. Yes, I know there are others out there and plenty of documentation. The goal here is for me to fail along the way and learn how everything works. I'm also not just going to go and rip off what others have done. So while I will be looking at the Alktronic and the like, I don't plan on doing exactly what they are doing right now.
All in all, thank yo all for the help. If anyone wants to really help out let me know and we can better figure out the plan for a group based project like this.
Thanks!
Scanned over most of the posts and here are some thoughts based on those:
1. I have tried weighing the liquids as an alternative but found the scale to be a pain in the butt to accurately get a measurement. It might just have been the cheap load sensor I had but either way I just didn't like some of the challenges that were to be if I went that route.
2. I know there are better pumps out there and eventually I will add support for the better stepper based pumps for for now the goals are to hopefully eliminate the need for an accurate pump and also to keep the overall product small.
3. Yes, I know there are others out there and plenty of documentation. The goal here is for me to fail along the way and learn how everything works. I'm also not just going to go and rip off what others have done. So while I will be looking at the Alktronic and the like, I don't plan on doing exactly what they are doing right now.
All in all, thank yo all for the help. If anyone wants to really help out let me know and we can better figure out the plan for a group based project like this.
Thanks!
rygh
Community Member
What sort of help do you need?
Water drop sensor:
http://farm4.static.flickr.com/3589/3341699447_7047edb530_b.jpg
Water drop sensor:
http://farm4.static.flickr.com/3589/3341699447_7047edb530_b.jpg
rygh
Community Member
Concerns:
As you drip your "basic acid" (yes, you wrote that. funny.), how will you mix?
Wait a very long time between drips?
Shaker table?
CO2 level may change during measurement if it is really slow, affecting PH.
As you drip your "basic acid" (yes, you wrote that. funny.), how will you mix?
Wait a very long time between drips?
Shaker table?
CO2 level may change during measurement if it is really slow, affecting PH.
Let me know if you need any CNC parts and so on... I know someone 
Interesting project!
When using a pH probe keep in mind you only need the reversal point around ph ~4.5 as your endpoint, so no real calibration necessary. Also the "waste" is only sodium chloride in slightly acidified seawater, if you dont do many tests a day Uor have a super-nano tank) it should be absolutely safe to pump back the sample from the titration chamber into the sump. - so no "waste" generated.
Best,
Christoph
When using a pH probe keep in mind you only need the reversal point around ph ~4.5 as your endpoint, so no real calibration necessary. Also the "waste" is only sodium chloride in slightly acidified seawater, if you dont do many tests a day Uor have a super-nano tank) it should be absolutely safe to pump back the sample from the titration chamber into the sump. - so no "waste" generated.
Best,
Christoph
Urbanknight
Active Member
I can help! BUT..... Only count on me as your main cheerleader! My knowledge of electronics comes from the book of "Electronics for Idiots."
Cheerleaders are the bestI can help! BUT..... Only count on me as your main cheerleader! My knowledge of electronics comes from the book of "Electronics for Idiots."
+1
Dont get distracted and stay on your course. Fail fast, fail often. Whatever is your initial hypothesis, that you want to test out, go for that. Irrespective of what route you take, you are likely to encounter issues. I would advise sticking to the bare minimal circuit to test the hypothesis (drop count based quantification and ph based detection of titration point). Staying minimal in terms of complexity will reduce time and effort required and detect any systemic issue early on.
I have been planning to build my own monitor for quite awhile now. I finally broke down and bought an Alkatronic. Neat unit, I had been following it's progress since Jonas first started developing it. I like the Alkatronic, but will need more monitors for other tanks, and they are too expensive to be used with secondary systems. So having an open source version is really important to me.
I have not cracked the Alkatronic open yet to see what they have inside yet, but based on what they were planning to use, and what I recognize from the outside, I would suggest you look at the same (or similar) components as they appear to be using largely off the shelf stuff. The embedded board is an RPI with an Atlas Scientific Tentacle daughter board. This is their PH interface and interface for 2 of their pumps, also Atlas Scientific (alk pump and waste pump). They have 2 off the shelf stepper pumps (they look like Kamoer heads). For the stepper drivers for the 2 stepper pumps, again an off the shelf hat like the Adafruit DC & Stepper Motor HAT for Raspberry Pi should be fine (depending on the stepper motor current requirements). Their BNC interface is likely using a custom board, but the same thing might be doable using a I2C DAC breakout board.
So I will be following along and may be able to lend a hand or ideas if I see up dealing with something I have knowledge off. My first suggestion was going to be to investigate a load cell as the means of measuring the sample and reagent. It sounds like you have already tried this with poor results. I was thinking that a appropriately sized LC would allow to forego calibration of the pumps as taring the LC at the beginning of the test cycle would be enough.
Dennis
I have not cracked the Alkatronic open yet to see what they have inside yet, but based on what they were planning to use, and what I recognize from the outside, I would suggest you look at the same (or similar) components as they appear to be using largely off the shelf stuff. The embedded board is an RPI with an Atlas Scientific Tentacle daughter board. This is their PH interface and interface for 2 of their pumps, also Atlas Scientific (alk pump and waste pump). They have 2 off the shelf stepper pumps (they look like Kamoer heads). For the stepper drivers for the 2 stepper pumps, again an off the shelf hat like the Adafruit DC & Stepper Motor HAT for Raspberry Pi should be fine (depending on the stepper motor current requirements). Their BNC interface is likely using a custom board, but the same thing might be doable using a I2C DAC breakout board.
So I will be following along and may be able to lend a hand or ideas if I see up dealing with something I have knowledge off. My first suggestion was going to be to investigate a load cell as the means of measuring the sample and reagent. It sounds like you have already tried this with poor results. I was thinking that a appropriately sized LC would allow to forego calibration of the pumps as taring the LC at the beginning of the test cycle would be enough.
Dennis
Any updates here?
This has been on my mind again recently, and I'm digging through my design files and other ideas I had in this space. The principle is all the same really, just needs some implementation
Here is the titration chamber I knocked up a long while ago to be 3d-pinted. It has a spot to hold a pH probe, and an integrated drain. I never solved the agitation problem (maybe we just shake the whole assembly?).
I was planning on using a 1.0 or 0.1N standard HCl acid solution as the titration medium (removes a number of unknowns to use an off the shelf acid, plus you can buy it in gallons).
In retrospect, the titration chamber is likely far bigger than it needs to be, but having more liquid allows us to overcome errors in dispensing, cleaning, and other concerns. I also had no housing in mind when I made that chamber, but will look for something suitable.
This has been on my mind again recently, and I'm digging through my design files and other ideas I had in this space. The principle is all the same really, just needs some implementation
Here is the titration chamber I knocked up a long while ago to be 3d-pinted. It has a spot to hold a pH probe, and an integrated drain. I never solved the agitation problem (maybe we just shake the whole assembly?).
I was planning on using a 1.0 or 0.1N standard HCl acid solution as the titration medium (removes a number of unknowns to use an off the shelf acid, plus you can buy it in gallons).
In retrospect, the titration chamber is likely far bigger than it needs to be, but having more liquid allows us to overcome errors in dispensing, cleaning, and other concerns. I also had no housing in mind when I made that chamber, but will look for something suitable.
I have not worked on a DIY version yet. I recently however had an experience with my Alkatronic that highlights the need for an open source solution.
I was at work and checked on the graph for my frag tank and was shocked to see that there was huge drop in the most recent measurement (~8.3 -> 5.9 dKH). The Alkatronic detected the huge swing and re-tested the measurement. Apparently the same or close enough for the Alkatronic to accept it as correct and dosed ~50 ml of alk into the frag tank to try and raise the dKH back to the minimum of 7.5 that I had preset. Being at work my head was racing as to what the possible cause could be. the only thing I could think of was that my ATO was stuck on and the overfilling of RODI had dropped the alkalinity of the tank (along with the salinity). At that point no one was home, but I sent out an urgent request for a visual check of the sump level as soon as someone was back there. I did get a feedback on the sump level, normal, but as it happened, there was a 2 hour delay, and the Alkatronic did another test just before the report came in. The new test was 8.53 dKh, back in the neighborhood of the normal range, just a bit elevated due to the addition of extra alk by the Alkatronic.
The only thing that I can think of for this to occur, is that the tank sample must have been incorrect causing the reagent to drop the PH down faster than normal causing the dKH to be interpreted as lower than it is. There is a micro filter inline in the sample line, but something must have obstructed the sample line for at least a couple of tests causing a partial sample, the low readings, and dosing to kick in. There was no major harm done in this event, but if the accuracy had not returned to normal, then I could see where this could have wiped the tank by the addition of all the extra alkalinity due to faulty readings.
As I contemplate a 3 week vacation in January, I may just set the frag tank size to a fraction of its real size to lower the calculated alk dose just incase this scenario played out again while I am away. I would be giving up the ability to boost too low alk levels, but alk spikes worry me more than alk too low.
For any DIY version, the addition of a way to detect similar occurrences would be desirable.
Dennis
I was at work and checked on the graph for my frag tank and was shocked to see that there was huge drop in the most recent measurement (~8.3 -> 5.9 dKH). The Alkatronic detected the huge swing and re-tested the measurement. Apparently the same or close enough for the Alkatronic to accept it as correct and dosed ~50 ml of alk into the frag tank to try and raise the dKH back to the minimum of 7.5 that I had preset. Being at work my head was racing as to what the possible cause could be. the only thing I could think of was that my ATO was stuck on and the overfilling of RODI had dropped the alkalinity of the tank (along with the salinity). At that point no one was home, but I sent out an urgent request for a visual check of the sump level as soon as someone was back there. I did get a feedback on the sump level, normal, but as it happened, there was a 2 hour delay, and the Alkatronic did another test just before the report came in. The new test was 8.53 dKh, back in the neighborhood of the normal range, just a bit elevated due to the addition of extra alk by the Alkatronic.
The only thing that I can think of for this to occur, is that the tank sample must have been incorrect causing the reagent to drop the PH down faster than normal causing the dKH to be interpreted as lower than it is. There is a micro filter inline in the sample line, but something must have obstructed the sample line for at least a couple of tests causing a partial sample, the low readings, and dosing to kick in. There was no major harm done in this event, but if the accuracy had not returned to normal, then I could see where this could have wiped the tank by the addition of all the extra alkalinity due to faulty readings.
As I contemplate a 3 week vacation in January, I may just set the frag tank size to a fraction of its real size to lower the calculated alk dose just incase this scenario played out again while I am away. I would be giving up the ability to boost too low alk levels, but alk spikes worry me more than alk too low.
For any DIY version, the addition of a way to detect similar occurrences would be desirable.
Dennis
Doesn't the alkatronic also just dose 0.2 dkh when low (unless manually disabled in setting) as an extra step of protection in this situation? And when there is that big of difference it tests in 2hr even if the user settings are longer? Seems like they built in a lot of safety features.
Yes I believe this is exactly how it operates. However in my scenario the faulty reading would result in the 0.2 dKH being added and then 0.2 dKH 2 hours later, and another 0.2 dKH 2 hours after that, etc. Until the tank was either way out of my chosen band, or the blockage had cleared and the true reading could be ascertained and the socket disabled. In my case the blockage cleared after 2 or 3 re-tests, but if it had not, and I was far far away on vacation, then the outcome would have been different. The alkatronic relies only on the dosing pump's accuracy for the sample volume. Another means of cross checking the sample volume would help to avoid a similar occurrence in any proposed version we come up with.
Dennis
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