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'[PIC] Making a very simple optical guitar tuner - '
2011\05\26@084647 by V G

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Hey all, after seeing this (http://das-labor.org/wiki/Stimmmopped/en), I
wanted to make my own very simple guitar tuner.

My schematic: http://postimage.org/image/32mp0tnpg/

- The chip in the middle is a PIC16F886, surface mount.
- The six LEDs on the left indicate which string is selected (E, A, D, G, B,
e). Small, surface mount, low power.
- The four LEDs on the right are used to shine light at various pulse
frequencies on the strings. High brightness, through hole.
- The push button switch selects the string.
- The toggle switch turns the power on and off.
- An ICSP header is placed somewhere on the board.

- The circuit is intended to be powered off of a few parallel 3V coin cells..



1. If the circuit is designed to run at 3V, how will programming be done by
the PICKIT2? The PICKIT2 runs on 5V as far as I remember, but I think it
should have an option to program at 3V, but I don't remember, been a while
since I used it.

2. The PIC16F886 datasheet says that the PIC can be run at 20MHz. Since I'm
tuning strings which I don't think divide nicely to those frequencies, I
want to run the PIC as fast as possible to minimize the error. Therefore,
I'm going to be using a 20MHz crystal. The datasheet schematic shows the
crystal with capacitors. What should the values of these capacitors be?

3. I didn't look much into it, but I use the 16F886 as a "jellybean" part.
It's cheap, available, small, and loads of features. I think the timers on
there should be adequate for the oscillation of the pins. How would you guys
recommend generating the right frequences for the LEDs? Timers

2011\05\26@091226 by Oli Glaser

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On 26/05/2011 13:46, V G wrote:
{Quote hidden}

Interesting you should bring this up again. I just finished making a little kit (16F690) which I intend to shove on our new website at some point in the near future. The prototype works pretty nicely.
All pretty simple really, the trickiest part was working out all the tuning frequencies, choosing which temperament and stuff. I borrowed quite a bit from the Stimoppped source, although I've done a few things differently. I chose high brightness red LEDs (not white as the forward voltage is too much for a coin cell which I decided on to power it) as they work better than standard ones for this purpose. A largish capacitor and small series decoupling resistor helps to lower the surges on the battery.
Don't worry too much about the error - I'm using an 8Mhz as running the 16F690 at 20MHz requires higher than 3V. The error you can achieve at this clock rate is way past anything that will be audible if you do the calculations - Wiki has a lot of good info on tunings - check out Scientific Pitch Notation, Cent, Equal Temperament pages.
Caps on the crystal should be around 10-20pF, the datasheet will have recommendations. I use 15pF on an 8MHz.
I generate the pulses using the 16-bit timer 1 interrupt set for 1/10 the note period. That way you keep the uC free to do other stuff like check buttons and display notes.
If you need any more help with any of it let me know.

2011\05\26@092147 by Mark E. Skeels

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I didn't look at the stuff you guys made or the links you posted.

But use a dsPIC and do all 6 strings (or 12!) at the same time.

:-)


Mark Skeels
Engineer
Competition Electronics, Inc.
TEL: 815-874-8001
FAX: 815-874-8181
http://www.competitionelectronics.com

2011\05\26@170438 by Yigit Turgut

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Your title is misleading, what you are talking about is a standard
tuner - not detecting the frequency of each string by using optical
spectrum waves. Yes it is also possible.

On Thu, May 26, 2011 at 4:22 PM, Mark E. Skeels
<spam_OUTmskeelsTakeThisOuTspamcompetitionelectronics.com> wrote:
{Quote hidden}

>

2011\05\27@003432 by Carey Fisher

face picon face
On Thu, May 26, 2011 at 5:04 PM, Yigit Turgut <.....y.turgutKILLspamspam@spam@gmail.com> wrote:

> Your title is misleading, what you are talking about is a standard
> tuner - not detecting the frequency of each string by using optical
> spectrum waves. Yes it is also possible.
>
> On Thu, May 26, 2011 at 4:22 PM, Mark E. Skeels
> <mskeelsspamKILLspamcompetitionelectronics.com> wrote:
> > I didn't look at the stuff you guys made or the links you posted.
> >
> > But use a dsPIC and do all 6 strings (or 12!) at the same time.
>
> > Mark Skeels
> > Engineer
> > Competition Electronics, Inc.
> > TEL: 815-874-8001
> > FAX: 815-874-8181
> > http://www.competitionelectronics.com
> >
>

I have a free app on my HTC Incredible smartphone that will generate any
note or listen for any specific note and show how far off freq it is.  It is
basically a universal musical instrument tuner.  Works with all the tempers
etc.  Kind of amazing actually

2011\05\27@010953 by Oli Glaser

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On 26/05/2011 22:04, Yigit Turgut wrote:
> Your title is misleading, what you are talking about is a standard
> tuner - not detecting the frequency of each string by using optical
> spectrum waves. Yes it is also possible.

I wouldn't say so - it can be called an optical guitar tuner.
The definition of Optical is: adj. visional; of the eye; of vision
This tuner uses vision during the tuning process as opposed to a "standard" tuner which would convert vibration of the string to an electrical signal for processing.

2011\05\27@185148 by Yigit Turgut

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Well, you might be right from a point but when you are talking about a
specific device - tuner - you are talking about it's main/core
functionality which is detecting the frequency of a vibrating string.
Output/feedback of this core functionality is in optical form. All
tuners feedback the player by a led/indicating sound or analog scale.
I believe 'optical guitar tuner' expression is not quite right. Maybe
it's just me thinking this way, if it's - sorry for the pollution.

On Fri, May 27, 2011 at 8:08 AM, Oli Glaser <.....oli.glaserKILLspamspam.....talktalk.net> wrote:
{Quote hidden}

>

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