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07-23-2010

Optical string-tuning tool

This tool assists you in tuning your string instrument to a given tone. It utilizes the stroboscopic effect to give feedback about the adjustment of your instrument. The two LEDs on the board blink with the frequency that the chosen tone has. When the string vibrates with the correct frequency, two lines are projected at a fixed position on the string. If frequencies don't match, the lines appear to be blinking or moving to the observer's eye. The moving or blinking effect decreases with decreasing difference between the two frequencies.

Menu

The "Stimmmopped" has two switches to choose the tone and instrument. Switch S1 toggles the current mode of the menu, which is either "choose instrument" or "choose tone". The 7-segment display displays the current selection. In the instrument selection mode, the display is lit up a bit brighter. Switch number two (S2) selects the tone or instrument in the given mode.

Here's how the menu is structured:

Displayed
character

Name

Explanation

b

Bass (5-string or dropped)

b0 (string 5), d1 (string 4 dropped), E1 (string 4),
A1 (string 3), d2 (string 2), G2 (string 1)

b.

Bass (5 string) lower halftone

A#0 (string 5), C#1 (string 4 dropped), d#1 (string 4),
G#1 (string 3), C#2 (string 2), F#2 (string 1)

G

Guitar (normal & dropped)

d2 (string 6 dropped), E2 (string 6), A2 (string 5),
d3 (string 4), G3 (string 3), b3 (string 2), E4 (string 1)

G.

Guitar (normal & dropped) lower halftone

C#2 (string 6 dropped), d#2 (string 6), G#2 (string 5),
C#3 (string 4), F#3 (string 3), A#3 (string 2), d#4 (string 1)

When the menu is in tone setting mode, the tone and octave are displayed alternating.

Since the device is battery powered, it switches itself off when no button is pressed for a period of 30 seconds. It may also be manually switched on and off by holding down the S2 switch. In normal usage conditions the battery will last for about a year.

Circuit board

The board is designed to be used as a plectrum. Here's the layout:
 

Optical string-tuning tool


Optical string-tuning tool
Click to enlarge

Optical string-tuning tool


Part list

Amount

Part

Description

1

ATmega48-20AU

Microcontroller

1

8,0000-HC49U-S

 8MHz Quartz

3

CR 2032

Battery (a set of 3)

1

KZH 20-1

Battery holding unit

2

NPO-G0805 22P

Capacitor for the Quartz

2

SMD-0805 47,0Ω

Resistors for the LEDs

8

SMD-0805 560Ω

Resistors for the 7-Segment

2

LED 5-4500 RT

LEDs for the strings

2

X7R-G0805 100N

Capacitor

2

TASTER 3301

Switch

1

SMD TAN.22/20

Capacitor

1

SA 39-11 GN

7 segment display


Source

Sourcecode & Layout can be found in our svn right here.

Links

Information about midi notes 

das-labor.org

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Fragments of discussion:Full version of discussion »
  • Not all stringed instruments can be configured with the help of this device. Tuning is best done through the microphone. The signal to be written in the microcontroller and compared with the standard.

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