Monday, February 11, 2013

Sunday/Funday/Op Amp day

So I have been working on building my own spectrophotometer for the Chromochord. I was trying to use a camera but the resolution is just not high enough to measure slight changes in absorbance at least by any way I could measure it. I guess I never tried looking at the raw pixel values but ehh fuck that. I need something easy that I can interface with electronics and a computer.

Can't even see the yellow protein? That is what I want to be able to measure.

So I started messing around with photoresistors and photodiodes. I have a bunch laying around because I loves me some light. I have these nice photoresistors that fit perfectly in a well of a 96 well plate and they can actually measure absorbance. I have no calibrated it yet or tried to test how precise it is. But using a really dilute solution of my light activated protein I could measure a difference in absorbance using a Blue LED compared to a buffer solution (the protein has an absorbance maximum around 450 nm!! which is what blue light is). I wired it up to my arduino to measure the changes in resistance of the photoresistor.

Then I was messing around with a photodiode which somehow generates 0.4V in ambient light? I think this one might have been a little more expensive than the $0.02 photoresistors from China. I will need to find the manufacturer but I think I purchased it from digikey and spent $5 or $10.  I used a TL084 op amp and a 1Mohm resistor to provide a large gain. Without the op amp it goes from 0.4V in light to 0.12V with my hand over it. With the op amp we see a 2V change with 4V being applied from external power supply. I used the op amp as an inverting amplifier as you see in the video how instead of going down the voltage goes up in the dark. With the 1MOhm resistor I receive a 7 fold gain. I think it should be 10 fold... hmm Yeah my circuit seems a little weird it was late and I just threw shit together. It works though. I need to go back and learn more! Damnit!

The stupid blog inverted my video, how appropriate.

I was thinking about this yesterday. I cannot possibly learn everything. In fact I am really stupid when it comes to electronics and I don't know if that will ever change. If i will ever become fluent enough that I can create an original circuit. Like in program there is a moment when you finally understand the code and the language enough that you can write any program from scratch. I feel that I am a far way away from the with electronics. One only has so much time and brain power. Where should one spend it? There is so many things I wish I could learn. So many things I wish I could do but I don't have an infinite amount of time. I think for me that is an important part of life. Figuring out what I want to do and how best to position myself to achieve those goals. Yeah it would be great to study the violin and be a chess grandmaster but in the end I just want to do cool science. I want to combine bio and electronics things. I want to use the power of statistics and programming to find cool features in data and learn about everyday things. It sucks that I don't have the time to do everything I want to do.