This document describes a sound to light system that converts music signals into light pulses using three colored LEDs. It employs two operational amplifiers with a total gain of 1000 times to amplify the signal from an electret microphone. The amplified audio signal is then rectified and used to drive an NPN transistor and control the intensity of the LEDs in rhythm with the music. The circuit automatically adapts to the music volume and can operate off a single 9V battery, making it suitable for small, private sound-to-light applications.

1. Submitted to :-
Ms. VARSHA DRABLA
Ms. AARTI SHARMA
Submitted by :-
HARISH KUMAWAT
session : 2010-11

2. A sound to light system converts music
signals into light pulses.
 base channel indicate the ‘beat’ of the
music by a more or less rhythmical flash,
while the other two represent the higher
frequency ranges of the music channel.
The ‘private’ version of a sound to light
system employs three colored LEDs
instead of powerful flashing lights or
floodlights as used in most discos.

3.  Another peculiarity of the circuit is the automatic
sensitivity adaptation to the music volume detected. In
this way, the circuit can work without any control.
 The circuit always draws an average current of 20 mA
and works happily off a 9V PP3 block battery.

4. The objective of this project is to generate the
light patterns in rhythmic manner.
A music-to-light modulator is a circuit which
controls the intensity of one or more lights in
response to an audio input.
Arguably there’s no less pleasure in enjoying
dance music in the privacy of your home, study or
students digs.
However, the true disco feeling is not obtained
without a matching sound to light unit, so here’s a
really smaller version.

5. Low power dual operational
amplifier

6. FEATURES OF LM 358
can be directly operated off of the standard +5V power
supply voltage.
Wide power supply range:
Very low supply current drain (500 µA)-essentially
independent of supply voltage
Low input offset voltage: 2 mV
Differential input voltage range equal to the power
supply voltage
Large output voltage swing.
Wide bandwidth (unity gain): 1 MHz

7. A microphone is an acoustic-to-electric transducer or
sensor that converts sound into an electrical signal.
used in many applications such as telephones, tape
recorders, karaoke systems, hearing aids, motion picture
production, live and recorded audio engineering,

8. An electret microphone is a type of condenser
microphone, which eliminates the need for a polarizing
power supply by using a permanently-charged material.

9. WORKING
SOUND
SOURCE
FILTER
SYSTEM
LOAD
AMPLIFICATIO
N UNIT
TRANSDUCER

10. WORKING

11.  We have employed two operational amplifiers with the
total gain of 1000 times.
 The input of the first op-amp is connected to the
electret microphone capsules via capacitor C2.
 microphone is given a certain DC bias level obtained
from the 9V supply rail by resistors R1 and R2.
 Capacitor C2, then, ensures that the microphone bias
level does not appear at the op-amp input.
WORKING…

12. WORKING….
It means, it will only pass the alternating component,
which is caused by the sound picked up by the
microphone.
Because of the two resistors have same value, the
supply voltage is effectively halved, i.e., 4.5V exists at
the junction of R3 and R4.
This bias voltage will also exists at the output of the
first op-amp and, because of R7, at the input of the
second one also, whose output will also copy this DC
level.
In this way, R3 and R4 keep boththe op-amps biased
at half the supply voltage.
First op-amp has a gain of 100 while the second op-
amp has a gain of about 10.

13. WORKING…
 signal level at the output of first op-amp is
rectified by diodes D1 and D2, smoothed by C6 and
then used to drive n-p-n transistor T1.

14. FILTERS:-
consist of simple RC network…........
Fc = 1/(2πRC) Hz
low-pass section R12/C9 is dimensioned for about 160
Hz using 10Ω (R12) and 100 nF (C9).
To prevent the transistor bases from being charged
with negative levels, anti parallel diodes (D3, D5, D7) are
used on each base terminal

16.  Cell phone background lights for rhythmic
flashing according to the ringtone or incoming
call alert.
 In disco and party lounges.
 In music players and amplifiers.
 Simple sound-to-light unit for music,
 Sound indicator.
 For the hearing impaired : can be used to
indicate the telephone
 Door bell.
 In musical fountains.

17.  Less no. of LEDs are used..
 Circuitry is complex.
 Can only be used at small scale.

18.  by increasing the number of LEDs used.
 can be used at a large scale for commercial
purposes such as in discos, parties, etc.
 LEDs in the system is replaced by the large light
sources such as bulbs.
 fluorescent lamps can also used to save
consumption, in place of bulbs.
 increasing the number of filters used in the
system.