DIY water tester build

[shoedy]

After a lot of inspiration on this forum I'm currently working on my own water tester for alkalinity, calcium and magnesium which will be as compact as possible and fully integrated with Home Assistant for scheduling tests, publishing results and be able to automate dosing based on said results. I'm planning to fully open source the device, including embedded software based on ESPHome, parts lists, assembly instructions and 3d designs in fusion 360. Trying to aim for 100USD in materials to build the device, and it should also be able to work with other tritations such as phosphate and nitrate testing.

This thread is meant as a way to get feedback from the community at an early stage to improve upon the design in effort to make it more accurate, reliable and hopefully also easier to build for others. My background is in software engineering so any help with the mechanical- or chemistry side of things would be much appreciated.

Source code so far can be found at: https://github.com/dylanschoenmakers/reefgenie

Mechanics
This device uses two stepper motors, one for the peristaltic pump and the other as a valve actuator to pump different kinds of fluids (tank water, waste water, reagents) in and out of the reactor chamber where the tritation takes place. It features a drop sensor to increase accuracy of dosed reagents as an additive method of just running the pump to N seconds. The color sensor will detect color changes needed to compute the quantity of the trace elements.

I've looked at the designs of water testers that are available on (or almost on) the market and where most vendors use a combination of a pump with solenoid activated pinch valves I tried to replace the need of 5-6 solenoids with one stepper motor and a cam-follower design to pinch the selected tubes when needed.

I'll still need to add an enclosure and a reagent bottle tray to this design.

Here's a test of the valve actuator:
I'm currently away from home (on a trip in the US) so this a bit of an older design but it may give some insight on the operation of the actuator.

Software
I'm developing the software to run the routines in c++ within the esphome platform for easy use in Home Assistant. It will control the stepper motors and use the sensor information from the colorimeter and the drop sensor to allow calculation and ultimately reporting of alk/cal/mag levels.


Chemistry
Does anyone have any suggestions on what reagents to use? ABCReagents has been unresponsive to numerous requests from my side so I have to look for other options.

 

[Formulator]

Well done! What do you mean ABC has been unresponsive? Are you trying to get them to tell you what their reagents are comprised of?

 

[braaap]

Email them. He has been extremely responsive to me.

I’d be very interested in buying a parts kit to build this.

 

[robinm]

Why not use any of the commercially available test kits that have only liquids as their reagents? For example Salifert dKH, API calcium & Red Sea Pro magnesium. That way builders are guaranteed to be able to get reagents in their locale.

 

[shoedy]

Thanks for the replies so far. I'll try to reach out to ABC on e-mail again. I just want to know if there's anything I could calibrate their solution and my device with.

@robinm That is exactly what I'm planning to do. I have the Salifert test kits at home but not all of those are in 100% liquid form. ABC has a kit that will give you probably 6+ to years of reagents worth.