Faraday’s law of induction is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (EMF)—a phenomenon called electromagnetic induction.
In this electronic circuit we use Faraday’s law of electromagnetic induction to create music. We re going to make an instrument which will have a stretched copper wire placed near a magnet. When you pluck the wire and it vibrates, EMF is produced in the copper wire and it produces musical notes.
IC1 – LM386 low-power audio amplifier
T1, T2 – BC549 npn transistor
LED1 – 5mm LED
Resistors(1/4 watt, ±5% carbon):
R1, R6 – 4.7k ohm
R2, R3 – 2.2k ohm
R4 – 470k ohm
R5 – 1k ohm
R7 – 10 ohm
VR1 – 100k ohm potentiometer
C1 – 0.01uF ceramic disk
C2 – 47pF ceramic disk
C3 – 1uF, 25V electrolytic
C4, C7 – 0.1uF ceramic disk
C5, C9 – 100uF, 25V electrolytic
C6 – 470uF, 25V electrolytic
C8 – 10uF, 25V electrolytic
CON1 : 2-pin connector
BATT.1 – 12V battery
S1 – On/Off switch
LS1 – 8 ohm, 0.5W speaker
Let us begin:
1.Connect a Red wire to BATT.1’s +ve terminal and a Black wire to its -ve terminal. Connect the Red wire to one of S1’s terminals and continue the Red wire from S1’s other terminal.
2(i) Connect IC1’s Pin 6 to the Red wire and Pin 4 and Pin 2 to the Black wire.
2(ii) Connect Pin 1 to C8’s +ve terminal and then connect C8’s other terminal to Pin 8. 2(iii) Connect C9’s +ve terminal and one of R7’s terminal in parallel to Pin 5 of IC1. Connect C9’s other terminal to one of LS1’s terminals and Ls1’s other terminal to the Black wire. Connect R7’s other terminal to C7 whose other terminal will be connected to the Black wire.
2(iv) Connect Pin 3 to the output terminal of VR1.
3(i) Connect R6 to the Red wire and its other terminal to LED1’s +ve terminal. LED1’s -ve terminal will be connected to the Black wire.
3(ii) C6’s +ve terminal will be connected to the Red wire and its other terminal will be connected to the Black wire.
3(iii) Connect R5 to the Red wire. Connect C5’s +ve terminal, R2 and R1 in parallel to R5’s other terminal.
4(i) Connect R2’s other end and C3’s +ve terminal in parallel to T2’s Collector. C3-s other terminal is connected to VR1 and then connect VR1’s remaining terminal to the Black wire. Connect C5’s other terminal to the Black wire.
4(ii) Connect R4, R3 and C4 in parallel to T2’s Emitter. R3 and C4’s other ends are connected to the Black wire.
5(i) Connect R1’s other terminal, C2 and T2’s Base in parallel to T1’s Collector.
5(ii) Connect T1’s Emitter to the Black Wire.
5(iii) Connect C2’s second terminal, C1 and R4’s other terminal in parallel to T1’s Base.
5(iv) Connect one of CON1’s terminals to C1’s second terminal and CON1’s other terminal to the Black wire.
6(i) Take a long copper wire(guitar strings) and tie it between the nail with correct tension.
6(ii) Take a wooden plank of size 10cm x 30cm approximately and nail four nails on either side of the plank.
6(iii) Connect the wire’s ends to CON1’s terminals.
The two-stage preamplifier, designed with BC549 transistors, amplifies the low signal produced by guitar string. The string produces voltage in the range of ~3mV and the preamplifier amplifies the signal further to ~20mV.
LM386 (IC1) is a low-voltage audio power amplifier, suitable for battery-powered devices for hobby projects.
VR1 is the volume control and is connected between the output of the preamplifier and input of the power amplifier.
For the original article on the project, click here.