Microcontroller guitar tuner

[D.M.]

I have a Parallax Propeller kit and was wondering if there can be a way to input a microphone to measure the frequency of the sound wave coming from a guitar string (eg. guitar tuner)

**broken link removed**

 

[Space Varmint]

Give us a link to the kit.

 

[D.M.]

Here:


**broken link removed**

 

[audioguru]

Why do you need to measure the frequency?
If you are deaf then the frequency doesn't matter.
If you can hear then use a tuning whistle.

 

[D.M.]

im trying to make a tuner.

if pluck a string from my guitar the string oscillates at a specific freq... if i wanted to make sure the string was in "tune" i want to compare it to the freq i am aiming for.

even if i was deaf, the guitar string can still be out of tune.

 

[Space Varmint]

You know they make those?

I would need to see the device your talking about before I would know if you can convert it or not.

 

[D.M.]

i understand they make guitar tuners. keyword "they". I want to make one for my sake, to say i did. nothing like over engineering small projects


but
i think i may have figured it out.


thanks anyway

 

[birdman0_o]

There is always the time and place for "just buy one". If you really want to do this project, we will gladly help you. It's little things like this that give the biggest kick sometimes

Have you ever used a uC before?

 

[D.M.]

yes, actually im in an introduction to microprocessors class. we started out by learning assembly language (which i hate) and now we've moved on to this Parallax Propeller uC.

We will then move on to the PIC Kit 3.

i wanted to try to make a guitar tuner for the end of the semester project. other people in class are making a motion detection light switch (too plain).

a guitar tuner seems a little more advanced.

i am going to ask my teacher today

 

[birdman0_o]

It will be a lot of work, but fun at the same time !

 

[Rhythmtech]

Frequency to voltage IC's are available. You may need to amplify the signal from the guitar to the F/V converter. For which you could probably use an op amp. Then run the output from the opamp to the F/V converter. The output from the F/V converter will need to be 0 - 5 volts for the uController so you would have to design for that. Then you will need to map an analog input on your uController and calibrate it to be able to convert 0 -5 volts into a number you read as frequency. So you would need an output like and LCD for that.

The other option is to use a voltage to frequency converter and output a tone to tune to using the ucontroller to set the voltage.

Freq to Volts converter that might work, I didn't look too closely at the specs...
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=LM2907N-ND


On second thought you could set an led on a pwm output and have it get brighter the closer you are in tune, might be simpler than an lcd. you would need to be able to instruct the ucontroller which freq you are looking for eg: Switch in pos 1 tells ucontoller to look for the A which you set in code as whatever voltage 440 Hz is output from your F/V converter.

 

[Nigel Goodwin]

Frequency to voltage IC's are available. You may need to amplify the signal from the guitar to the F/V converter. For which you could probably use an op amp. Then run the output from the opamp to the F/V converter. The output from the F/V converter will need to be 0 - 5 volts for the uController so you would have to design for that.

That would be the poorest and least accurate way of doing, and far more complicated than required.

You simply need to process the incoming signal, and read the frequency of it directly in the PIC.

EPE did just such a project a number of years ago.

 

[Rhythmtech]

Well, ideas are the point of forums. Please elaborate on processing small signals with the pic input, I am interested as well I am sure as is D.M. How accurate do we need to be?

 

[Nigel Goodwin]

Well, ideas are the point of forums. Please elaborate on processing small signals with the pic input, I am interested as well I am sure as is D.M.

You don't process it inside the PIC, you process it externally - just as you would have to if trying to use a F to V converter. Basically amplify it and filter it, guitar notes aren't pure, and it's the fundamental frequency you want, not the harmonics.

The EPE example I mentioned used filters controlled by the PIC to do this.

Commercial guitar tuners (at a fraction of what building one would cost) use DSP's to do the job.

 

[Rhythmtech]

I agree with everything your are saying. Sometimes finding an expensive poor way to do something is more fun than buying the off the shelf solution though.

 

[Brevor]

This has been done many times, Try Googeling "PIC guitar tuner"