ll parts to come from one 181x181x3 mm plate that can be ordered at Pokono/Formulor/RazorLab. You will find the required SVG file of the latest evaluated version above.The attached PDF file illustrates the layout.
If you use another laser cutting service and/or plate size, you may have to rearrange the pieces so they fit to this format. You may use Inkscape to modify the layout of the SVG-file.
To ensure a clean snap-together of the parts, the material thickness has to be 3.0 mm precisely. I would recommend not to use materials with surface modifications, as they may be a bit thicker.
5mm LEDs, the topic has been discussed in detail in another section. For colorimetric applications use a neutral white LED.
Screws, nut and washers:
- Four M3 x 20 mm screws and four M3 nuts. I am using nylon screws, but brass or steel would work as well.
- Two M2.5 x 10 screws, two M2.5 nuts and four plastic M2.5 washers to fix the breakout to the sensor holding plate. The washers act as distance pieces and have to be made of plastic or cardboard. Do not use metal washers, as they may come in contact with electronic parts of the sensor breakouts and cause shortcut and damage!
I am using jumper cables to connect breakouts and LEDs with the breadboard or the header of the Pi Zero. In the first case female/male in the second case female/female cables are required. They should be sufficiently long.
Silicon rubber feet:
I add four small self-adhesive pieces of silicon rubber as feet below the base plate. You may get them at the next hardware store or use something else.
- A few drops of glue to assemble the lid. Any kind of plastic glue or super glue should work.
- A bit of adhesive tape, to fix the housing. This allows you to stabilize it but to change sensors or LEDs later.
- Standard plastic photometer cuvettes.
Step 9: Additional Information: LEDs
Emmision maxima of some commercially available bright 5 mm LEDs with narrow emission angles. Please notice that this are only suggestions, as only a few of them have been experimentally validated with the device.
These LEDs are blindingly bright, to avoid to look directly into the light beam!
UV: Nichia NSPU510CS, 375 nm (3.3 V)
5004PCH02, 405 nm (3.5 V)
violet: YDG-504VC, 412 nm (3.5 V)
blue: Kingbright L-53MBC 455 nm (3.4 V)
Nichia NSPB500AS, 470 mn (3.2 V)
cyan: Nichia NEPE510JS, 495 nm (3.1 V)
green: Nichia NSPG500DS, 520 nm (3.2 V)
yellow: Yoldal YZ-Y5N15N, 590 nm (2.1 V)
orange: Avago HLMP-EH1A-Z10DD, 615 nm (2.1 V)
red: Kingbright L-7113SEC-H, 630 mn (2.1V)
Red, orange and yellow LEDs may require a 60 Ohm resistor to reduce the voltage from 3.3 to 2.1 V (@20 mA).
UV and violett LEDs are out of the range of the sensors, but might be used for fluorescence experiments.
Step 10: Software
Here you find my recent versions of the programs for the colorimeter.
TCS34725 RGB Bradspi ...py is a modification of a script developed by Brad Berkland. All credits go to him, the ugly part is mine. (http://bradsrpi.blogspot.de/2013/05/tcs34725-rgb-color-sensor-raspberry-pi.htm).
My script is asking you for a name of the sample, then read the values and tries to translate them into RGB values. For optimal RGB calculation you need to enter to enter blank (water/buffer w/o dye) values measured previously into the code as reverence values. At the start and the end of the measurement it is asking you if you like to stop measuring, "Y" stops.
The other three Python script are based on a recently released script for the tcs34725 by Adafruit.
You need all three in combination. The script allows to perform slow kinetics. You must enter the name of the sample, the number of measurements and the time, in seconds, between measurements. Results are written, with a timestamp, to the shell and to a CSV file.
Any hints, improvements, corrections are welcome.
The scripts for the TSL2591 will be added later.