How to Design Schematic Circuit of Electronic Organ.

 This is an interesting experiment in audio which would make a nice toy for children.

This circuit produces a musical note by pressing a key on a keyboard. The sound is produced by a small speaker. The electronic organ will play only one note at a time, but the number of notes

is unlimited. Different tones can be selected by pressing different keys, as in a common electronic organ. Tonal range is determined by C1, which can be altered within a large range of values. Values between 0.022uF (for higher notes) and 1uF (for lower notes) can be experimented.

You can also use this circuit as a multi-tone bell in your home or to monitor several places at the same time. Replacing the keys with different sensors (reed switches, for instance) will produce different tones when closed.

A schematic diagram of the simple Electronic Organ is given in circuit l. The circuit consists of a simple two-transistor oscillator. The transistors are direct- coupled and drive a small loudspeaker.

Components layout, using a terminal strip as chassis is, shown in circuit 2. The circuit can be housed in the same box as the keyboard.

ln Figure 3we show the layout of the keyboard. Each trimmer potentiometer is used to adjust individual notes.

The circuit can be powered from AA cells or a power supply ranging from 3 to 6 volts.

The keyboard can also be made from a printed-circuit board or with small metal plates. When each metal plate is touched by a probe the corresponding circuit closes and a musical tone is produced.

Parts List - Electronic Organ

Q1 - 8C548 general-purpose NPN silicon transistor

Q2 - 8C558 general-purpose PNP silicon transistor

51-4 - keyboard- 

P1-4 - 1,000,000 ohm trimmer potentiometer

R1 - 10,000 ohm, 114W,5% resistor

C1 - 0.047 uF ceramic or metal film capacitor

C2 - 100 uF,12 WVDC electrolytic capacitor

55 - SPST toggle or slide switch

81 - 3 or 6V - AA cells

SPKR - 4/8 ohm, 2to 4 in. - small loudspeaker.