Simple Guitar Sensing

I am working on a student project demonstrating basic Arduino literacy.

I want to rig up a guitar with six sensors, one for each string. Under the sound hole, I want to place a neopixel ring. Then I want to do some basic programing so that the light will be different depending on what note or combination of notes are being played.

I do not want to measure frequency or sound or pitch... I just want Arduino to respond to whether or not a note is being played.

I would love any general advice, but especially what type of sensor can best accomplish this.

Thanks!

Well, considering that many different notes can be played on a string depending on where the fingers are on the fret bar, you are going to have to address the frequency issue unless you mean you just want to know which string has been plucked - although that can be a problem too since the nearby strings will resonate to some degree. I believe (you need to research this) that the normal pickup on a guitar is a magnetic pickup with a core under each string and each core has a magnet in it. As the string vibrates, it changes the magnetic field and the coil core creates a small voltage from that variation in the magnetic field. At least, those are the ones I have seen.

Each pickup coil produces a different voltage waveform for each string and is then wired together. What you need to do is to unpick this and wire each coil separately. Each will need a separate amplifier ( an op amp ) and input to the Arduino. You might want to put an envelope follower on each analogue input as well. The signals will need to be mixed with an other op amp to feed to the sound amplifier if needed. Your big problem will be hum pickup. It will not work with nylon strings.

A guitar with a sound hole is usually an acoustic guitar with nylon strings and no pickup coils.
Acoustic guitars can have internal piezo pickups and amplifier outputs.
If not, then the only option I can see is adding a piezo pickup with preamp and e.g. a MSGEQ7 spectrum analyser chip.
Leo…

While nylon strings are possible on an acoustic guitar most of the acoustic guitars I have seen have steel strings. You can get an electric pickup for these. Some are basically a sound box microphone but others are of the pickup type.

Thanks everyone.

I should have been clearer... for the purposes of this project, I just want Arduino to know if a string is currently in use.

If the project is a massive success, I may continue down that road, but for now just keeping it simple.