If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
Registered Member #97
Joined: Thu Feb 09 2006, 05:40PM
Location:
Posts: 61
I built a colorimeter out of some legos, an LED, and a CDS cell. It is crude, but it works. I have an red led for a light source and a CDS cell for a sensor. From what I understand the CDS responds linearly with respect to the intensity of light.
I added the paper shims to keep the cuvette straight. During operation I covered the colorimeter with a black T-shirt to keep out any light and I used a multimeter to measure the resistance of CDS. Below is a Beer's law plot for blue food coloring. The concentration is in drops/cup of water.
Registered Member #1497
Joined: Thu May 22 2008, 05:24AM
Location: Toronto, Ontario, Canada
Posts: 801
You should completely seal off the top of the cell, and as well, you should (if you haven't already) run a blank with just the solvent, in this case water. You should definitely try and get a fine beam of light as LED's scatter light, and as you know Beers law incorporates path length, scattering light would muck up the calculations. Perhaps put the LED at the end of a long tube with black paint on the inside to absorb any light that isn't mostly headed straight forward, and similarly for the CdS cell.
Without wide spectrum light sources and monochromators, this isn't going to be the best useful tool, however it would be useful if a known RGB LED (ie: one on digikey, mouser, etc that has quality control) that can have its spectra run for each of the R, G, B elements, you could build a crude spectrophotometer.
A RGB LED spectrophotometer could always be useful, if you need to find the concentration of something you could always use a known concentration as a reference point, however one problem is that the extrapolated E value cannot be compared with literature values, as a LED spectrophotometer would not be monochromatic.
Also keep in mind that you would have to run blanks with everything, but this could be a practical tool...
Ex: You wanted to find the concentration of Cu2+ in your etchant when it is fully oxidized: start with excess HCl w/ known volume, add in a known amount of copper, wait for complete dissolution, then use that to calibrate and find the E value. Unfortunately having thought about it, Cu1+ also affects the colour, so it would be tricky to determine how saturated the solution was, but it could have its uses....
Registered Member #193
Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022
I think a black T shirt probably seals off the light well enough (and the data tends to support that), The first thing I'd chance is the bits of paper; if you paint them black you will get rid of a lot of "stray" light. It would also be interesting to see how it fairs with 1 drop in 2 cups of water and 1 drop in 3 cups etc.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Lego Colorimeter
