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Hi!

Im doing yeast cultivation experiments in test tubes and like to check the turbidity(optical density) within the tubes (register growth). I would like to have 10 tubes in parallel and register the turbidity at different time points. Construction ideas? LED, Photoresistors or other devices ? How to register the data on single in/output pin? I might run more samples and want the construction to be easily expanded (more tubes)

Have anyone seen similar projects?

Thoughts, comment, suggestions ??

"Im bored of checking each culture in the big expensive spectrophotometer..."


« Last Edit: December 14, 2007, 06:03:07 pm by Funhough » Logged

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if you can find a spectrometer with variable resistance or other easily measurable output, it should be pretty straight foward. Just use the analog inputs. It should be expandable to the number of analog inputs available...

Sorry I don't know too much about what you're trying to do, but no one else was responding to your post. Maybe this will get a conversation started.                                        
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Hi!

I think I have some ways to solve the "tiny spectrophotometer" project. Searching the net I found som spectromety pages and from that  VIOLA! Im thinking of making a circuit made of a white LED and a tiny optical filter(not realy needed but...) for lightsource. To collect the light passing through the sample Im thinking of using an light sensor (LDR). The LDR will serve as analog in and the resistance change can be converted to actual growth of the cells(the tube is slowly getting darker...)....
The two circuit I will mount on a pipe of some kind (Im making a dummy out of a toilet paper roll  smiley) This to keep it in the dark but the question that im struggeling right now is :

Should the LDR be directly in front of the LED or 90 at the side,thus collecting the spreading of the light?

The whole "core apparatus" can the be made in series (hmm ten toilet rolls in a row...) Im thinking of using the same pin as Analog IN and puls the LED to collect the light from individual tubes.
To finally wrap up the construction Im going to connect a servo to mix the samples (45-45 degrees roll)...

Other suggestions welcomed....Ok! I could take a piece of sewer(?)plastic pipe and drill holes in it and do all the wiring inside to simplify the sunlight problem and put the samples directly into the big sewer tube (small tubes into a big tube) and then use the servo and rock the whole thing(Hmm...may need a bigger servo...)

Now...back to playing around with the Arduino...learning how to plot the data in Processing....and save the files...

Fun!!!
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If your meassurings need to be comparable from tube to tube, you will need some way to calibrate the LED/LDR combo.

LDR's have a qiute high tolerance, so even if you buy 10 of the same their actual resistance when exposed to the same light might vary quite a lot.
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Hi!

Yes, the LED/LDR will be calibrated, individually against a commersial spectrophotometer. Im waiting for the parts to arrive so I can start. I will keep you posted on the project...

Now im searching for a datalogging/sketch /How-to-tutorial... so I can store the data from 15 min (1 reading 10 values) up to three days (total 288 readings/10 values). This data can then be exported and plotted in Processing (simultaneously..hmm.) or as I prefer imported into Excel.

Suggestions welcomed!!!
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If your system can be hooked up to a Pc, i think that would be the easiest way to do tha datalogging, sine the Arduin board only has  1KB RAM to hold data. That would hardly be enough for 288 * 10 readings.

There was a post in one of the other threads the other day about realtime datalogging to Excel by help of a smal 20$ shareware program that would read data from the serial port and deliver it to Excel. That might be interesting for you.
« Last Edit: January 06, 2008, 01:32:19 pm by MikMo » Logged

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Yes ,the Arduino will be connected to a PC...for a start at least. I would like a stand alone application but for now Im satisfied with PC connection (and pass it through the internet to my personal computer...). "Realtime datalogging" CHECK! I will search for it!
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Just found the other thread

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1198963150
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/* Hi again!

Things evolve in rapid pace;

I found this:ftp://http://www.tigoe.net/pcomp/code/category/code/processing/122#more-122

time for;

Setup() Project Spectrophotometer1...

The Processing code should work fine for my project. and I will save the file as "growthcurves.csv" so I can import it directly into Excel.

I will soon show picures of the hardware...

Stay tuned...
« Last Edit: January 09, 2008, 04:46:47 pm by Funhough » Logged

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