Picture of Photocell Piano
Inside photocell piano.JPG
This tutorial is a how to construct a 6 note “Photocell Piano”. When the user runs their hand over the top of the keys (photoresistors) they turn on audio notes, which can be tuned with potentiometers. This project utilizes Arduino to turn the notes on and off. The tutorial includes a parts list, schematics and the code required to operate this musical device.

This device requires two separate circuits and an Ardunio code.

1) A circuit that contains all the notes.
2) A circuit that mixes all the notes.
3) The code
Photocell Piano(516x290) 17 KB
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Step 1: Note Maker

Picture of Note Maker
Part One

Note Maker


100n Capacitor- (x6)
10u Capacitor- (x6)
100nf Capacitor- (x6)
1k Resistor- (x6)
220k ohm Resistor- (x6)
Photoresistor- (x6)
10k Variable Resistor- (x6)
Arduino Uno- (x1)
10” by 4”Prototype Board- (X1)
555 Chip- (X6)
Mono Audio Jack- (x6)
Switch- (x1)
9V Battery- (x1)
Prototype Shield for Arduino- (x1)
Arduino Prototype Shield- (x1)
1/8” Audio jumper cables-(x6)
Small Speaker with 1/8” cable- (x1)

Note: The 100nf capacitor is added so that the variable resistors only control their individual note. If they were not present all the variable resistors would control all the notes making the circuit only have one tone. 

Solider all parts to the 10” by 4” prototype board. Please note that the photo resistors control the notes so place them in a location that is convenient to play. Use stranded wire and an Arduino prototype shield to interface Arduino to the 555 circuits.

Step 2: Audio Mixer

Picture of Audio Mixer
+9v and -9v.jpg
Part Two

Audio Mixer

6” by 4”Prototype Board- (X1)
741 Chip- (x1)
Mono Audio Jack- (x7)
10k Resistor- (x8)
Switch- (x1)
10k Variable Resistor- (x1)
9V Battery- (x2)

Note: The notes will sound if the audio mixer if off. This is because the sound travels through the 10k resistor into pin 6. The reason for the mixer make the sound less distorted.  

Note: This circuit requires +9v and -9v. This can be tricky so refer to the drawing above.