Reagent Robot

Reagent Robot
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The idea here is to remove human variability and provide for automated data collection with low cost chemical reagent tests for common water conditions such as Ammonia, Chlorine, Nitrate/Nitrite, and pH. Currently, the electronic sensors for those test are very, very expensive and require frequent replacement.
This thing shows a possible design for the reaction chamber where the chemical indicator is added to the sample water and LED/photodetector combination is used to test the color of the resulting mixture. This design is not meant to be a final product, but instead just a starting point.
The bottom plate simply has a hole drilled part way through for the stirrer/cleaner shaft to sit in. A single ball from a bearing would be dropped in the hole to reduce friction and extend the life of the "bearing". Initially, this plate could be plex, but eventually should be something more durable.
The center (clear) area is a square block of plex with a larg