Edge Collective

UV Spectrophotometry

Designing a DIY UV Spectrophotometer

Quick links


Kearns et al have been working to develop lower-cost methods of testing that leverage a particular feature of biochar (and similar filters): some contaminants adbsorb much more easily than others. It turns out that the presence of one class of more weakly-adsorbed contaminants -- dissolved organic matter -- is relatively easy to assess with a lower-cost laboratory method: UV spectrophotometry.

The details of this approach are laid out in a 2020 article by Kearns et al:

And specific instructions for performing the UV absorbance test are laid out in the supplementary section, here:

Further: while commercial UV spectrophotometers used in such tests are usually over $2000, there are several designs available for DIY forms of the instrument, costing under $100 in parts. We found one design to be particularly simple and well-characterized:

Our aim is to build a working prototype of this UV spectrophotometer, compare its performance to similar commercial instruments used in a laboratory, and then see if such an instrument might be easy to build and use in a community workshop setting.

Misc notes

Sun Mar 3 08:35:31 PM EST 2024

Building the circuit

Precision voltage to current converter

Adafruit 4-pin jumper cable here

Adafruit 4-pin jst ph stemma here

Adafruit JST 4-pin jst ph stemma SMD here

Mon Mar 11 05:20:16 PM EDT 2024

LED polarity

uv detector IN-C35PPCTGU0

datasheet here

custom footprint:

emitter v_0.1 ordered 3/11/24

detector v_0.1 ordered 3/12/24

Fri Mar 15 11:00:43 AM EDT 2024

instructrable on 555 as switch mode supply

Sat Mar 23 03:52:20 PM EDT 2024

Solder mask goof-up on UV emitter part!

Reference for UV emitter IN-C35PPCTGU0

Also: two pins on Q1 on emitter are 'flipped' -- need to fix pins -- was able to solder 'upside-down' anyway to fix

Mon Mar 25 08:17:39 PM EDT 2024

Made a quick 3d enclosure using openscad:

openscad and stl files are here

Fri Mar 29 08:57:08 PM EDT 2024

Water filtering, 1 micron

Selection at McMaster here

Nice pairing on Amazon:

Most recent prototype

Fri Apr 5 08:31:52 PM EDT 2024

Working on detector v_0.2 ...

Sub-schematic that will be moved to a 'control board':

Version 0.1 footprint assignments:

Version 0.1 pinout:

(need to add 2.5V ref)

Fri Apr 5 11:01:04 PM EDT 2024

Detector schematic:

Emitter schematic:

Revision 0.2 of emitter and detector

Sat Apr 6 10:25:06 PM EDT 2024

Edited footprint for LED (remove solder mask from center pad)

Revising mosfet pin assignment on emitter ...

2N7000 datasheet

2N7000 pinout:

emitter ver 0.2

Sat Apr 6 10:22:42 PM EDT 2024

board layout:



board files:

detector ver 0.2

Sat Apr 6 10:22:55 PM EDT 2024

board layout:



board files:

Mon Apr 15 08:18:11 PM EDT 2024

Collecting water samples and filtering through 1 um filter ...

3/4" NPT male + 3/4" barb fitting on Amazon

electric water transfer pump on Amazon

calibration of total organic carbon / uv254, EPA document pdf

uva254 go

'request a quote' for uva254 go here

might want to search for 'total organic carbon' (TOC)

An easy spectrophotometric acid-base titration protocol for dissolved organic matter

correlating uv254 to TOC, BOD, and COD video

Great paper on UV254 methods and applications. Note: correlations between uv254 and disinfection byproducts! references here