Detecting Specific Wavelength of Light using a Photodiode

Projects General Guidance
1

Hi All,

I am currently undertaking a project for my degree at university where we are given the task to track sound and light from 1m away, and guess who got stuck with tracking the light. I have tried using some LDR's with the Arduino Uno and it worked perfectly fine but I found that the range only went up to about 0.5m (at best) which is not acceptable. So, I have switched to using a photo diode for the time being and I was just wondering how I can detect a specific wavelength of light with that device? (note I have to track red light which it's wavelength is about 620-750nm I think)

Any help is much appreciated :slight_smile:

2

Basically you can't, you have to fit some sort of filter infront of the diode like an interference filter. You also need an instrumentation amplifier to get a decent signal from a photo diode.

3

Use an [u]optical filter[/u].

You probably will need an interference type filter depending on how narrow the filter needs to be and on how much rejection you need.

4

LEDs are wavelength sensitive and produce a voltage in response to light, but only in a rather narrow band 50-100 nm bluer than the normal emission maximum. Try using a RED led as a photodiode in your application.