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 :)) 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!!!