DIY spectrometry on a tap water sample

[xavi]

Let’s show and describe and document some use of Home-made DIY spectroscopy step by step.
(you can also run seed BioAssay to perform an broader investigation on water issues)

Test and investigate water chemio-physical aspects

Here we will use 3D Printable Fiber Spectrometer Kit

[xavi]

• Fiber Spectrometer Step by Step Instruction – Version 1 (archive).

There are no soldering stages for this first learning approach to assembly. Soldering may be required to power the LED with a 3V coin battery so that the kit can be transported and used in the field to analyse water samples directly in situ.

As mentioned is th Step by Step, you also need to be able to plane a few very small lugs in plastic 3D printing.
A small pair of pliers for handling the 2 films is essential.

[xavi]

First Rainbow Spectrum

You can now plug in the USB cable to your computer to make a first test. On you computer just use a Web-Cam software to see the image.
According to Step-by-Step documentation above:

• On Windows 10 use the per-installed “Camera” software.
• On Mac you can use the “Photo Booth app”.
• On Linux “guvcview” is a good and free software.

With the app started you might need to switch the camera (to USB2.0 UVC HD Webcam) to see the spectrometer. At first you might just see a black screen. Now point the spectrometer towards a lamp or to the sun and you should see the rainbow spectrum.

In our experiment here and now we are using Archlinux with: following outputs from journal after plugin the device:

usb 1-1: new high-speed USB device number 5 using xhci_hcd
usb 1-1: New USB device found, idVendor=1e45, idProduct=8022, bcdDevice=58.05
usb 1-1: New USB device strings: Mfr=3, Product=1, SerialNumber=2
usb 1-1: Product: HD Camera
usb 1-1: Manufacturer: Suyin
usb 1-1: SerialNumber: 200910120001
usb 1-1: Found UVC 1.00 device HD Camera (1e45:8022)

and

$ v4l2-ctl --list-devices
HD Camera: HD Camera (usb-0000:00:14.0-1):
	/dev/video2
	/dev/video3
	/dev/media1

BisonCam,NB Pro: BisonCam,NB Pr (usb-0000:00:14.0-7):
	/dev/video0
	/dev/video1
	/dev/media0

So, we use qv4l2 command line interface to open a generic graphical webcam configuration tools, then in this tool we opened /dev/video2 and we obtained :

.

Next Steps bellow:

• Fitting the fibre optic light collection device
• Assemble the light source
• Perform a calibration test with distilled deionised water in the cuvette.
• Test with https://spectralworkbench.org/
  • Many software access issues to be solved

Quick and dirty test with SpectralWorkbench without any optic light collection device

[xavi]

When we checked the results of the 3D printing of our CuvetteHolder.STL, we found that the slots for the optical fibre and the light-emitting diode were blocked by excess printed plastic. We had to cut with a very thin blade, sand with a suitable file and test the light passage with a high-intensity LED.
We can now move on to the final assembly

[xavi]

Here’s the set-up for our first attempt.

This first was a failed one. The light spectrum captured at the output is virtually black

So we have to dismantle everything and inspect the entire chain: light / fibre optical / slot / optical slit