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Light To Sound Circuit

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Mahmoud El-tabey

on 30 December 2014

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Transcript of Light To Sound Circuit

The circuit purpose / Theory
of the the light controlled sound circuit is to convert electromagnetic waves "light" into longitudinal waves "sound"
The circuit components
• Speaker 8 Ω
• cross over capacitor
• IC NE555
• decoupling capacitor
• timer Capacitor
• Resistors
• Power Source
Light-Dependent Resistor
is a light-controlled variable resistor. The resistance of a photo-resistor decreases with increasing incident light intensity; in other words, it exhibits photo-conductivity.
When the electrical current flowing through the voice coil changes direction, the coil's polar orientation reverses. This changes the magnetic forces between the voice coil and the permanent magnet, moving the coil and attached diaphragm back and forth.
Cross over capacitor
A passive crossover has no active filters as were used in the electronic crossover. It uses coils (inductors) and capacitors to cause a roll off of the audio level above or below certain frequencies to prevent unwanted portions of the audio from reaching the various speakers. The simplest types use a single coil OR capacitor connected in series with the speaker. If a capacitor is used, the capacitor will tend to block the lower frequencies. If an inductor is used, it will tend to block the higher frequencies
IC NE555 Timer
Light To Sound Circuit
The Circuit Diagram
is that by using light deminent resistor as mentioned before, its resistance changes according to intensity of light ,with changing of light intensity the the values of resistance changes and accordingly the input on the 555 circuit which changes the frequency of the input which in turn changes the frequency on the output leads due changing in the pitchiness of the sound from the speaker and taking into account that the peak voltage on the speaker does not change "amplitude constant" , but the frequency of the output.
555 have two main usage ,, here in this circuit we use 555 IC circuit as a base circuit to drive the speaker .
555 used as astable mode , and these drive the frequency and volt change pulses to speaker to work properly
other components
• decoupling capacitor ;

• resistors ;

• power source ;
used to prevent the effect of noise source to be applied to the out waves
used as charging and discharging channel of the timer capacitor
power supply 5 ,9 or 12 v used as a power source for the circuit
The Circuit Operation
the parallel resistor with LDR prevent the current to path through except a very small quantity that make noise to charge the capacitor ,,
when Light is applied to LDR it's resistance is to be law and the current pass through to let the Capacitor be charged and discharged through it , which make the 555 timer operates and then the speaker would work properly
Circuit Simulation
Application of
L/S converter
presented to /

Dr . Abdel Azeem Abdel salam
simplified by /

Karim El din Mohamed sec 1
Kareem Hesham sec 2
Mohamed Hassan sec 2
Ali Selim sec 2
Shehab EL din Ehab sec 2
Mahmoud El-tabey sec 3
Full transcript