Colorímetro de código abierto

Este proyecto detalla un colorímetro de código abierto , que está hecho de componentes electrónicos imprimibles en 3D y de código abierto. Esto es parte de un proyecto más grande para reducir el costo del equipo científico que utiliza hardware de código abierto . ^[1]

Fuente
Anzalone GC, Glover AG, Pearce JM. Colorímetro de código abierto . sensores _ 2013; 13(4):5338-5346. doi:10.3390/s130405338 acceso abierto

Abstracto
El alto costo de lo que históricamente han sido sensores y herramientas sofisticados relacionados con la investigación ha limitado su adopción a un grupo relativamente pequeño de investigadores bien financiados. Este documento proporciona una metodología para aplicar un enfoque de código abierto al diseño y desarrollo de un colorímetro. Se analiza un colorímetro imprimible en 3D de código abierto que utiliza solo soluciones de hardware y software de código abierto y componentes discretos fácilmente disponibles y se compara su rendimiento con un colorímetro portátil comercial. El rendimiento se evalúa con viales comerciales preparados para el método de demanda química de oxígeno (DQO) de reflujo cerrado. Este enfoque redujo el costo de la DQO de reflujo cerrado confiable en dos órdenes de magnitud, lo que la convirtió en una alternativa económica para la gran mayoría de los usuarios potenciales. El colorímetro de código abierto demostró una buena reproducibilidad y sirve como plataforma para un mayor desarrollo y derivación del diseño para otros fines similares, como la nefelometría. Este enfoque promete un acceso sin precedentes a instrumentación sofisticada basada en sensores de bajo costo por parte de aquellos que más lo necesitan, los laboratorios del mundo subdesarrollado y en desarrollo.

Palabras clave

código abierto ; hardware de código abierto ; colorimetría; DQO ; Arduino ; reprap ; impresora 3D ; sensor de fuente abierta; demanda química de oxígeno; colorímetro de código abierto

Introducción

Colorimetric analytical methods are likely to be the most commonly applied methods for determining the concentration of dissolved species. Many dissolved species absorb light of a particular wavelength and the amount absorbed as the light passes through a given length of solution increases with increasing concentration the species; higher concentrations absorb more light than do lower concentrations. The relationship between absorption and concentration is defined by the Beer-Lambert law[2].

A colorimeter or a spectrophotometer is employed to measure absorption at a specific wavelength. Light is usually filtered to permit only a narrow band of light at the absorbance peak wavelength for the species measured. The apparatus typically reports results in concentration units but also reports absorbance units or transmittance.

Design files: http://www.thingiverse.com/thing:45443

Firmware: http://github.com/mtu-most/colorimeter

BOM

• Arduino Uno
• Adafruit LCD shield (http://www.adafruit.com/products/772)
• LED having peak around 606nm (like: LEF3833 http://www.jameco.com/Jameco/Products/ProdDS/333665.pdf)
• A suitable resistor for the LED you choose
• TSL230R light-to-frequency sensor
• Proto board (like: http://radioshack.com/product/index.jsp?productId=2102845&znt_campaign=Category_CMS&znt_source=CAT&znt_medium=RSCOM&znt_content=CT2032230)
• Conductors (Cat 5 cable works great)
• Black ABS or PLA filament
• 12 M3 screws (just about any length; 10-12mm is good)
• 12 M3 nuts
• 20 M3 washers

Instructions

1. Print the parts and clean them up so everything fits together nicely. Push M3 nuts into their appropriate slots at each corner of the case body - slots open to interior.
2. Cut the proto board down to size (about 27mm x 46mm) and drill holes to match those in the sides of the case.
3. Loosely attach the boards to the interior of the case with a couple screws each and push the cuvette holder into place (no cover) and mark the approximate locations where the sensor and LED must be placed on the boards to align with the windows in the cuvette holder.
4. Remove the boards from the case and solder the components to their respective boards at the points marked. Leave the LED leads a bit long so it can be moved to aim the beam through the hole.
5. Solder the conductors per the schematic. (The io pins can be soldered to directly on the LCD shield if you're careful, otherwise different means will be required, like not using the shield as a shield.)
6. Fit the boards back into the case, this time firmly.
7. Download and install the firmware on the Arduino.
8. Fit the LCD shield and power the device (surplus wall wart of appropriate voltage or USB power will work).
9. Place the cuvette holder back into position (no cover) and use the menu system to select "Calibrate". The LED will illuminate for a few seconds - make sure that the majority of light passes as straight as possible through the cuvette holder windows and impinges upon the sensor. If the LED/sensor are high or low, reshape the cuvette windows with a small rat tail file or suitably sized drill bit.
10. After the LED is properly aimed, remove the cuvette holder and align and affix the cover to the case with four M3 screws and washers.
11. Push the cuvette holder through the opening in the cover and check that the lid fits nicely into recess.
12. Follow the appropriate protocol for calibration (yet to be built into the firmware - forthcoming).

Applications

• COD^W

Media

• Joshua M. Pearce, "Open source 3D printing allows you to print your own cheaper health devices", Conversation, Feb. 28, 2014.
• 3D printing in the lab- Biolegend

See also

• Open-source Lab
• Open-source mobile water quality testing platform
• Open-Source Photometric System for Enzymatic Nitrate Quantification
• Open source optics
• Building research equipment with free, open-source hardware
• Open source science
• Open source 3-D printing of OSAT
• Open-source hardware

References