I want to build a simple optical pickup to detect the vibration of a guitar string. I was hoping to achieve this with a reflective IR sensor to minimize the pickups aesthetic footprint. I would like to eventually take the analog signal generated and input it into arduino to see if I can use string vibrations to trigger other events.
Would it be best to use a modulated IR signal (38KHz) and corresponding IR receiver?
if so...
Would a 4 channel IR breakout such as this one be modulated to 38KHz? I've looked at a few different variants of this breakout on different sites and I cant seem to find an answer.
IR Receivers are typically ON or OFF outputs. Did you want to get audio out of this pick-up or just an indication that the string was vibrating or not?
jeffd:
I just need an indication that the string is vibrating. No audio. So will this type of modulated IR reflection sensor be the right sensor for the job?
I would worry about ambient light and sensitivity. The optical difference between a steady string and a vibrating string is very minor. Have you thought about using a magnetic pickup? You would have to use separate coils for each string to tell the strings apart. To detect vibration you would amplify the signal and filter for the audio range.
Im to understand that using a modulated IR light source and a receiver set to filter all but the modulated frequencies should take care of the ambient light... or would this not be sufficient? I cant use a magnetic pickup because I need an analog output from each individual string. There are a couple DIY solutions online to making small magnetic pickups for each individual string but thats a lot of wire winding
I was wondering if a circuit like this would work:
It uses an IC LM567 Tone Decoder. The circuit I suggested before uses an IC LM339N Comparator. I guess Im not sure what the difference between a tone decoder and a comparator is... it seems in this instance they are serving the same function.
As for the weak signal response I would assume I could run the output through a signal amplifier?
I expect the tone decoder uses a modulated IR source and the comparator just compares agains a fixed analog level. Either one could work. Have you done a literature search? Maybe you aren't the first person to want to detect vibrations in tuned strings.
Has anyone had any success with optical pickups? I am building a bass guitar and would like to incorporate this technology. Any advice would be appreviated.
Remember your high school physics. The string may vibrate on a fundamental frequency or on any harmonics of that fundamental frequency. Your optical pickup will not be able to differentiate one from the other.
