he licence fee for the layout shall be used for this project, as I would like to give a number of the devices for an evaluation to schools or other other educational institutions.
- But as collecting all the required parts from different sources could be a hurdle, we think about setting up a small project to offer DIY kits that would alredy contain all parts, except for the Raspberry Pi, plus some cuvettes and consumables, so you may built your own device within a few minutes and start immediately with your first experiments.
So you might see a kickstarter project on this soon, and if you are interested in such a kit, please check this site again in late May.
- The part that may require the largest improvements is the software. I would appreciate if some skilled programmers would check my Python scripts and improve them. I would like to place links to your improved scripts in here, for public access. Please be aware that the basic scripts are licenced by Adafruit under the MIT licence, so any derivate should be as well.
- In this instructable I have used a few graphs taken from Adafruit and the data sheets of the sensors.
But there are also images I have copied from the web, but have lost the information from which sites. I would like to apologize for this and thank the owners of the images.
- If you like this project, please have a look to my other instructable on a Raspberry Pi-based microscope (Raspberry-pi-microscope ). The project got stucked a bit in the last months, as I have a busy full time job and a family, but may see some new developments soon.
- If you have any hints, suggestions or corrections, please let me know.
Step 8: Materials Required; SVG File
Raspbery Pi or Arduino
Adafruit TSL2591 breakout (for photometer, product ID 1980)
Adafruit TCS34725 breakout (for colorimeter, product no 1334)
You may use other sensors or breakouts, but you may have to modify the position and size of the holes in the sensor holding plate.
The acrylic pieces for the housing:
The current layout was optimized to allow all 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 va