Light operated Toy organ

Light operated Toy organ

The special feature of this circuit is that its output tone varies with the intensity of light. this circuit uses ic 741 as a square wave oscillator and the PNP-NPN transistor pairs as a push-pull amplifier. 

A fascinating project for the children love its music when handled uniquely. 

Know your Circuit

A schematic diagram of the light-operated toy organ is shown here. the circuit is elementary and straightforward. N0 complicated design is involved in configuring the circuit. However, Operation Amplifier IC 741 is employed here as a square wave oscillator as a vital component. 

Another important component is LDR (Light Dependent Resistor) which is familiar to many electronic hobbyists. LDR's resistance value varies with the intensity of light that falls on it. in this circuit, the LDR is used ingeniously to produce varied tones of music as output. 

The sound output is derived from the push-pull audio output stage for simplicity and performance. unnecessary use of a transformer is avoided in this circuit design.

Parts List 

Parts	Items	Quantity
IC	IC 741	1
Transistors	SL100	2
Resistors	100 K ohms	2
	470 ohms	1
	33 ohms	1
Capacitors	100 MFD 25V	1
	0.1 MFD	1
	0.01 MFD	1
Others	LDR	1
	9V Bulb	1
	Speaker 8 ohms	1
	9V DC Power Supply	1

Know your design

when a beam of light falls on the ldr the circuit produces a musical output. if this beam is obstructed by moving a hand to and fro in front of the LDR the resistance of the LDR increases and the oscillator frequency changes. Thus a fine variation in musical tones is produced. With practice, this circuit can be used to produce some sweet music. An LDR with a minimum light resistance of about 5k should be used. This can be a very exciting project for children. 

Know your assembling

As explained earlier the circuit design is very simple and costs less to assemble. 

in the audio output stage usage of a bulky transformer is avoided to save space as well as cost. This makes the circuit very compact and accommodates very little space. 

The circuit can be assembled on a general-purpose veroboard for simplicity and ease of space. 

Conclusion

Hobbyists and electronics enthusiasts can assemble this project and can be fit into a toy of their choice with light-interrupted design activity to produce various musical sounds. 

Please put your comments below so that the project can be improved and improvised into modern toys so that it attracts a large users in future.