further adventures in spectroscopy

Problem number one. A quick test using the set up as shown in the previous tests showed that I was using the wrong sensors. The TSL250s are really sensitive in low light levels but max out really easily, and maxed out in the light levels of the spectrum.

Problem number two. How to mount the organisms infront of the DVD material diffraction grating.

Problem one was easy enough to solve, make a new board using the more common kind of photocells.

With the sensors hooked up to the Arduino and reading the values in Max I could see that they were giving a value of about 0.75, which gives just enough room either side to read reduced or increased levels in each part of the spectrum. I’ll probably scale the inputs anyway, as I’m not expecting any kind of dramatic change.

The first idea for the organism container was to use some PDMS with a tiny chamber sandwiched between two glass slides. I made a small form for the chamber out of thin plastic and placed it on the slide, I then built a wall around the slide and sealed it to make the mold for the silicone.

The moulds were placed in plastic petri dishes in case of any leakage and the whole lot put in the oven for fast curing at 90º for 45 minutes.

Didn’t work.

The forms for the chambers had floated around inside the PDMS as it cured, making them in the wrong place and impossible to remove.

The second idea was to stick a small form for the chambers in the lid of a small petri dish, so that when it was cured and removed it could be pressed against a glass side to reseal. This way the chamber would be easily accessible and the sample could be added or changed quite easily. If the PDMS is well cast it will seal itself to glass quite readily.

This one worked much better.

The prism is just to hold the thing in place. There are about 5 or 6 tardigrades in the small square shaped chamber.

I need a bit more time to really see if this does anything useful or interesting, but I kind of like it so far. At the very least it will tell me what I need to do to make the second prototype much better.

2 thoughts on “further adventures in spectroscopy

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