lignment, connect the LED with your power source, in case adjust the allignment.
Now assemble the "photometer box" as you have done before. First run the cables through the holes in the back plate.Then stick the tongues of the two plates with sensor and LED into the holes of the back plate, add the front and side plates and place the box on the base plate.
I would recommend to place four small silicon rubber feet on the botton of the base plate.
!!! Do not glue the box, as you may not be able to disassemble it any more !!!
I recommend to fix the box it with a some adhesive tape, if required.The most recent, but yet-to-be-build layout will simplify assembly and fixation of the structure even further.
Finally assemble the lid. Glue the two pieces defining the lower edge to the lid plate. Then glue the handle to the center of the lid plate.To reduce reflection, you may add a piece of self-adhesive felt to the inner side of the lid.
Connect the cables to the corresponding ports of your breadboard, PI or Arduino and check for functionality of the sensor and LED.
Step 3: Setting Up the Raspberry Pi; Required Software
As both sensors are communicating via I2C, you will have to activate this on your Raspberry. In addition you may need to install the appropriate drivers/kernel support. As you can find very good and detailed instructions on this at the Adafruit website (Adafruit: GPIO/I2C setup), I will not describe this here in any detail.
If you succesfully have implemented I2C on the Pi, connect the sensor with Ground, Vin (I use 3.3V) SDA and SCL. In the case of the RGB sensor you also need to turn off the build-in LED by connecting the LED line with Ground. Check if the sensor can be found by entering "sudo i2cdetect -y 1" at the shell.
Unfortunatelly both sensors are using the same I2C adress, 0x29, so you can't use them in paralell.
Now you need to install some software to perform your measurements. Luckily Python programs to read the data from the sensors were already available, so I only had to modify the TCS34725 software provided by Adafruit (https://github.com/adafruit/Adafruit_Python_TCS34725) and the TSL2591 software by "MaxlKlaxl" (https://github.com/maxlklaxl/python-tsl2591 ) a bit to adjust them for my purposes. I like to thank both of them for their brilliant work.
In the accompanying software package you will find examples of programs that will allow to perform measurement series and kinetics with both sensors. As I am rather new to Phyton programing, the programs require some optimization, I appreciate any help. Depending on your light source and your specific application, you may need to change the data sampling time and/or sensor gain settings of the sensors.
White, UV, blue and green LEDs run at about 3.1 V, so you may power them directly from the Pis' 3.3V output. For yellow, orange and red LEDs you need a series resistor between LED and power, otherwise they will be distoyed. If you do not want to run the LEDs permanently, you may connect them to a GPOI and switch them on and off by software.
So far I have not performed any experiments with the Arduino or Trinket, but Adafruit provides libraries and scetches for both sensors.
Step 4: Performing Measurements
The device is built to measure aqueous solutions or suspensions by placing a standard photometer cuvette between LED and sensor. I am using disposable cuvettes made from polystyrene (PS) or acrylic, and both full volume and semi-micro cuvettes work. You may get 100 such cuvettes for about 12- 20 €, depending on type and material, and you may use them several times.
So basically fill a sufficient volume of the solution/suspension into the cuvette, place it in the device watching for correct orientation, close the lid and start to measure. Given you are using a Raspberry Pi, you will have to start a Python program that allows you to perform the type of measurement (single, multiple, kinetic) you like to. Some of my programs write the data to so called CSV (Comma separated values) files you may open with MS Excel or LibreOffice Calc, Word or Writer and sev