Editing BioBoard/Documentation/Optical loss
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In industrial production systems, such as large-scale alcohol fermentation, insulin production, etc., biological growth is often monitored using in-line ('live') sensors, which measure optical loss, usually at wavelengths in the [http://en.wikipedia.org/wiki/Infrared#Different_regions_in_the_infrared near-infrared] (NIR) or IR-A spectrum (700-1400nm). The inspiration for the home-built NIR probe described in the rest of this wiki is a [http://www.optek.com/Schematic_Single_Channel_NIR_LED_Probe.asp single-channel NIR sensor] from Optek, which emits and detects at 850nm, and is designed for in-line monitoring of yeast fermentations. | In industrial production systems, such as large-scale alcohol fermentation, insulin production, etc., biological growth is often monitored using in-line ('live') sensors, which measure optical loss, usually at wavelengths in the [http://en.wikipedia.org/wiki/Infrared#Different_regions_in_the_infrared near-infrared] (NIR) or IR-A spectrum (700-1400nm). The inspiration for the home-built NIR probe described in the rest of this wiki is a [http://www.optek.com/Schematic_Single_Channel_NIR_LED_Probe.asp single-channel NIR sensor] from Optek, which emits and detects at 850nm, and is designed for in-line monitoring of yeast fermentations. | ||
=Building a NIR probe= | =Building a NIR probe= | ||
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*how much can you afford to invest? | *how much can you afford to invest? | ||
Discussion of pros/cons of different source/sensor pairs | |||
This design uses an 850nm plastic LED as the photoemitter, and a matching phototransistor (Optek OP506B) as the photosensor. The transistors cost 80 cents each, and the required circuitry is limited to a couple of resistors. | |||
==What you need== | ==What you need== | ||
* | *IR LED | ||
* | *Phototransistor | ||
* | *1kΩ resistor | ||
* | *100Ω resistor | ||
* | *Wire | ||
* | *Soldering iron + solder | ||
* | *¾" acrylic tube | ||
*¾" acrylic discs | |||
*Acrylic cement (thick) | *Acrylic cement (thick) | ||
* | *1" PVC pipe | ||
*Aquarium glue/hot glue | *Aquarium glue/hot glue | ||
Optional: cell-phone motor (BubbleShaker Technology) | Optional: cell-phone motor (BubbleShaker Technology) | ||
==How to build it== | ==How to build it== | ||
Cutting acrylic and PVC | |||
Drilling holes | |||
Soldering wires | |||
Fixing diodes | |||
Glueing discs on tubes | |||
Plugging tubes | |||
Covering it up | |||
==Things to keep in mind== | |||
Biologically inert materials | |||
Food safety | |||
Aquarium glue vs hot glue | |||
=Interfacing and measuring= | |||
Arduino sketch should go here... | |||
=Calibrating= | |||
How to find out whether your measurements are accurate (do you need to know?) | |||
How to adjust (distance, resistance) | |||
=Making it cooler= | |||
Tuning to different substances | |||
Multi-channel measurements | |||
=Geeking out= | |||
In chemistry and biology, many different methods are employed to analyze the properties of a given substance. One method that is extremely useful in both disciplines is [http://en.wikipedia.org/wiki/Spectrophotometry spectrophotometry], the analysis of reflection or transmission properties of a material as a function of wavelength. | |||
techniques can be split into in-line ('live') | |||
* counting cells in a special microscope chamber, | |||
* marking cells with radioactive isotopes and counting scintillation events | |||
and off-line | |||
* incubating on solid substrates overnight and counting the resulting colonies | * incubating on solid substrates overnight and counting the resulting colonies | ||
* desiccating samples to measure total dry organic matter | * desiccating samples to measure total dry organic matter | ||
None of these techniques are very useful for monitoring biological growth over time, however, so photometry is often used instead. | |||
Reduction of light passing through a mass | |||
Absorbance vs. scattering | |||
=Links= | =Links= | ||
*Optek | |||
* | *Wikipedia | ||
*TruCell .pdf | |||
* | |||
* |