Capstone Week 1 - prototyping

Nitrate solutions of varying concentration

   This week was all about MQTT, Mosquitto, NodeRed, and the ESP8266. At the start of a new project it is important to hit all areas and find your risk items. For my colorimeter capstone that meant setting up the server, building and programming an embedded device, running first dashboard trials and taking real measurements.The results of each step in this first week prototyping process will determine the direction of the project for the remainder of the course. 

   The first risk item identified was the lighting source. Initially the LED was run off a 9V battery and resistor but an unstable spiking and then dropping off light level was measured. To accommodate this spike and drop an AMLD-6070Z LED power supply was added. This device was configured to have a constant but adjustable current output to stabilize the lighting source.

NodeRed flow for receiving colorimeter data and estimating nitrate

Dashboard for basic nitrate display & debug

  With only three data points and a preliminary sensor device the results are not completely solid. Averaging of 20 samples was used to remove noise in the sensor data. This will be combined with more data points on the calibration curve. No housing has been built, so there are other lighting consistency concerns to address moving forward. These concerns revolve around the repeatability of the light path going through the test tubes, and exterior lighting. Adding a housing which gives repeatable positioning between the light source, sample, and detector should also help improve these results. In addition it will block ambient light which will remove another variable from the lighting equation. 

 

First known sample results

    Overall the strategy for this project has been to hit the key targets, then improve each of those targets as time allows. That strategy will result in a functioning device with a full scope of improvements and risk items for device success. Moving across targets like this on a project is a critical skill to have in a career within technology development. Collecting user feedback involves rapid iteration and review. If a long time passes between the availability of functional software then the user can't provide feedback. By operating my projects in this fashion I can continually integrate user feedback by showing demonstration sections that operate.