This GitHub repository is intendied to serve as information and a guide to a low-cost chlorophyll flourometer. This fluorometer is based off of, In situ Measurements of Phytoplankton Fluorescence Using Low Cost Electronics and Hardware Selection and Performance of Low-Cost Fluorometers which can be found at https://doi.org/10.3390/s130607872 and https://doi.org/10.3390/s22062319 respectively.
This project is composed of a sensor packaged designed to induuce chlorphyll fluorescence and convert these values into readable measurments. This sensor contains a Particle Argon Microcontroller set to 2.30 firmware, an Arduino-Based Addalogger RTC with an SD card for data reading and writting, a TSL 2591 light sensor, an AW9523 GPIO Expander and LED Driver Guide and a Blue LED 430L for chlorophyll excitation. This design uses I2C comunication.
Stack the Argon Microcontroller on top of the RTC Addalogger. Connect the Argon Microcontroller to the 3.3V power source and Ground.
Set up I2C communication between the Argon Particle with the TSL 2591 and AW9523. Connect the SCL and SDA pins from the TSL 2591 Light Sensor and AW9523 GPIO Expander to the SCL and SDA pins on the Argon Microncontroller. Connect the TSL 2591 VIN pin to the 3.3V and GND pin to Ground. Connect the AW9523 VIN Pin to the 3.3V and the GND pin to Ground.
Set up the LED with the AW9523. NOTE: LED negative side is connected to the pin and the positive to the power. The LED will connect to the 0 pin on the AW9523.
Assemnple the housing. The housing will position the LED and the AW9523 at a 90 degree angle as well as will be an opage design as to eliminate any ambient light from impacting the measurements. This design will then be enclosed in a waterproof box. Design materials and models can be found at https://github.com/COAST-Lab/Chlorophyll-Fluorometer-/tree/main/Firmware
Callibrate the Sensor to convert Lux values to readable measurements, based off of commerical fluoromter values.
Begin water testing
After the fluorometer was constructed, tests were run where the LED was directly facing the light sensor in a dark enviornment. This test involved turning on the LED for 2 minutes and then off for 2 minutes for 5 rounds taking light measurements throughout. It was found that the LED was havign a steady increase in current casuing the light sensor to have an increase in values. 
After many trials of this the intensity of of the LED light was changed as well as the light sensor gain (sensitivity) value. The LED can be set to any intensity from 0-255 via the AW9523. The light sesnor can be set to a gain of low, med, high and max. The LED was found to have the least variability when set to an intensity of 100 and a when the light sensor was set to a gain of med. 
After many trials of this the intensity of of the LED light was changed as well as the light sensor gain (sensitivity) value. The LED can be set to any intensity from 0-255 via the AW9523. The light sesnor can be set to a gain of low, med, high and max. The LED was found to have the least variability when set to an intensity of 100 and a when the light sensor was set to a gain of med.
