Looking for an ammonia gas sensor through Google, I stumbled upon this page and had heaps of deja-vu. Enough so that I joined this community basically to talk about my ideas on this project. I had a very eerily similar idea over a year ago but my programming and electronics fell short of my objectives.
I hope that my ideas help development at least on the physical design stage:
- Use a good RGB light source (doesn't have to be bright or expensive)
- Use an LDR placed behind the mixed fluid to measure the light transmission:
- (basic test) R or G or B transmission if single chemical tester colour intensifies (such as in an ammonia or Nitrite test)
- (complex test) RGB transmission if colours change (like a wide range pH test). To deal with colour identification, it may be possible to feed R G B values through a converter to give Hue, Lightness, and Saturation values. Hue being the only important value in this case.
- Results can then be compared to a set of ranges which have been predefined when calibrating the chemical solutions. Provided the LED, LDR and chemical solutions are the same brands and versions in each kit, calibration needs only ever be done once per colour chemical tester.
1. I purchased some small non-medical sterile saline blood bags to store the chemical solution. Cheap, sterile enough and containable.
2. Ideally piezo pumps but they are crazy expensive. Not sure why as they are made from as few as 3 components (piezo, 2 sides of case). I bought some cheap piezo buzzers but never got around to building the cases and testing. Other option is using a small diaphragm pump to move liquids around. At the end of the day, the less liquids you move around, the less chemical solution you use up and the more consistent you can make your results.
3. A step motor driving a worm gear fixed to a syringe can handle the pumping in and out of test water. Combined with accurate chemical feeds, an array of one way valves, and a sediment pre-filter, you’ll be well on your way. Chemicals can't be fed with worm gear and syringe technique as temperature variations are likely to spill or suck liquids.
4. Excess water and waste solution from testing can be ejected for evaporation or sent to a “waste blood bag” for controlled disposal.
5. There’s no reason why this unit has to be big. I was thinking a solar panel & suitcase style operation. test values are then logged and/or sent by GSM or other means as a simple csv result. i.e. Date stamp, pH, Ammonia, Nitrite, Nitrate, GH etc…
6. Unit could be activated remotely or on a timer and would do the required level of “flushing” as to obtain a new fresh batch of water for every test done.
That’s basically as far as I got. I really wanted to create a portable kit made up of very standard and accessible cheap components and then open source the whole lot and create a purchasable kit from local suppliers for each continent. With that made, one could test for a huge range of chemicals, toxins, heavy metals, dissolved gasses… Huge potential and extremely flexible.