Universal Colorimetric Tester

[renesis]

Hi All,

This is something I've been wanting to do for years, and I think I finally found a sensor that will work. I've always had trouble reading the API tests, and I've always been miffed that the reefers get the cool digital test readers - and wanted to take a crack at building one that could potentially read any freshwater test given a blank/known concentration as a calibration.




A sensor came out from ams (AS7343) in 2022 that unfortunately has been made EOL, but has a replacement (TCS34488M) with a similar package that might work for future versions.


I recently got my hands on a qwic version of the AS7343 sensor from sparkfun, and figured its time to put together something.

Goals:

• As cheap as possible
• Universal as possible
• Fit API glass/plastic vials (not sure yet if the plastic vials will read ok)
• Start with Nitrate/Phosphate and see if I can add more there

I figure I'll need 2 light sources (warm white, and IR for reading the phosphate test), but can use the same sensor array across most tests. I can use a small-form ESP32 as the MCU to give it USB-C power, wifi/bt connectivity if needed, and keep it small. Small/cheap ~1.3" OLED screen for displaying results/selecting tests.

Enclosure will be 3d printed.



First pass at a sketch - I might drop the screen if I can give the device a web interface though, which will make the device even smaller/cheaper, reduces the need for physical buttons on the unit, and a 2nd pcb entirely. Also not sure if it will need a cover for the top of the vial, or how much ambient light will affect the reads. TBD. Will order some XIAO ESP32S3 to play with and see how far I can take it.

I'll log progress here, and am very open to suggestions and ideas. If successful, I'll release the files so it can be easily replicated.

 

[Naturescapes_Rocco]

Sign me up!

 

[JayP]

There are many similar freshwater devices designed for checking parameters of pool water, so why not aquarium water, especially when we have them for saltwater. What is it about freshwater aquariums that makes this difficult or just ignored by companies like Hanna?

 

[renesis]

There are many similar freshwater devices designed for checking parameters of pool water, so why not aquarium water, especially when we have them for saltwater. What is it about freshwater aquariums that makes this difficult or just ignored by companies like Hanna?

Exactly! I don't think it's difficult, I think it's just deemed that the market of people that would buy in is too small to justify the R&D.

 

[Akshay]

Hanna does have one for fresh water, it does all the tests no3, po4, NH4, K, Ca, Mg, S Fe2, Fe3 & PH ( model no HI83325)
i have one, but honestly it is not really required unless you are as nerdy as I am ,

if used properly you will know how many ppm of NO3 do your plants consume daily ( down to 0.1 ppm) , but is that really required? the difference between 17.5 ppm of NO3 & 20 ppm of NOP3 hardly makes any diff in plant growth

the Ca, Mg Tests are an abs waste , they just do not work

K is nice to know & I havent come across any other test that does the same

Fe2/Fe3 tests , this is useful , though whenever i test it always show Fe2=0 , so I am guessing it is not super accurate between the Ferrous & ferric , but total Fe is correct

also running the tests is quite tedious , & has to be followed to the T , if the method says shake vigorously for 1 minute, then it means 60 secs, if u do 70 secs or 50 secs you will get a different value , esp for tests like K
if the test says invert the cuvette 10 times , then 10 times it is & even the speed of inverting the cuvette makes a bit of a diff

Reaction time has to be followed to the second ( it does have a built in timer & auto reads the result after the timer has expired so that part is easy)

overall a fun toy to have , but frankly unless aquatic plants nutrition is your thesis topic , you can manage withought it

as for reading the drop tests, this is what I have done , I have made NO3 solutions of 1 ppm, 5 ppm, 10 ppm etc , run the no3 test , took a pic against a white background , kept pics for reference , I take a pic of the current test & compare the 2 pics

 

[JayP]

Well, I should have included "reasonably priced for the average aquarist" in my previous comment.