Greetings, I’m a chemistry teacher and would like to build a sensor for students to do measurements on fluorescent compounds.
While I have planned on learning more about Arduino I have not gotten around to doing it yet, so I am not completely certain that Arduino can help me with this project. I hope somebody here can give me some pointers.
The outline of what I want is a follows: A diode for exciting the fluorescent compounds, and two photodiodes for measuring two different fluorescent compounds (two different wavelengths). One compound changes its fluorescence based on pH and the other doesn’t, and I ultimately need to measure the ratio between their fluorescence.
I am planning on using a 20mA 3.2V LED to excite the compounds, and using optical filters to adjust what wavelengths reach the photodiodes. Once everything is together it would be ideal if the numbers could be sent live to a computer via USB, but right now I need to know that I can make the sensor electronics work.
I have tried to read up on light sensors, and my impression is that I need to use photodiodes as the light intensities won’t be very high – the highest intensity I home to measure would be visible to the naked eye if there are no other light sources, but not much more than that. My first problem is picking the photodiodes, I was thinking something like:
It is flat (makes it easy to place optical filters on it) and has a peak wavelength placed nicely in the middle of the visible spectrum. I assume I need some kind of amplification circuit, but I am not much of an electronics guy.
So my questions are as follows:
Can I have an Arduino run a LED and record signals from two photodiodes at the same time? A time resolution of about 1 second would be acceptable, but 10-100 ms would be neat. I assume this is doable.
Will the photodiode I found work well with Arduino, or can anyone suggest a replacement?
What kind of amplification circuit would work well with my photodiode (or its replacement)? I assume that I need an amplification circuit for each photodiode.
Ideally the circuit should be somewhat inexpensive, as the cheaper it is the more units we can afford and the more students can get one. It may be basic questions, but I’m hoping someone can give me some pointers so I can put something together for the students and focus on learning the Arduino elements relevant to this project first.