Photo organ LM324

We often hear electronic organs played on different occasions, but have you ever heard of a "photo organ"?

That's what we're going to build in this project. It's an original musical instrument that can produce different tunes according to the amount of light received by the CdS cell, and has a wide coverage of about three octaves.

The schematic lets you see that the DC current amplified by U1:A is carried to the U1:B, the integrating circuit, and U1:C oscillates a square wave according to the input voltage.

This output from U1:C is amplified by Q5 and activates the speaker. Q1 and Q3 are used to prevent the speaker from emitting a sound when the organ is not being played.

When you finish assembling the circuit, turn power ON and set the control volume in a position where the sound dies away when the CdS cell is exposed to the light.

Now shut off the light coming to the CdS cell with your finger, and the organ starts playing and changes its tune as you move your finger. Try playing your favorite tune by adjusting your finger position over the CdS cell.

Bill Of Materials For Photo organ
23 Resistors
Quantity: References Value
2 R1, R19 33k
4 R2, R4, R14, R16 10k
5 R3, R6, R11, R17, R23 100k
2 R5, R20 220k
5 R7-R10, R15 47k
1 R12 4K7
2 R13, R21 22k
1 R18 100
1 R22 470k
3 Capacitors
Quantity: References Value
1 C1 10uF
1 C2 0.01uF
1 C3 3.3uF
1 Integrated Circuits
Quantity: References Value
1 U1 LM324
5 Transistors
Quantity: References Value
4 Q1, Q2, Q4, Q5 2SC945
1 Q3 2N5401
2 Diodes
Quantity: References Value
2 D1, D2 1N4148
7 Miscellaneous
Quantity: References Value
1 - 4.5V
1 AUDIO 800 ohms : 8 ohms
1 BAT1 3V
1 RV1 50k







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