In this post we are going to construct a musical organ circuit whose musical tone can be programmed by adjusting 10 pre-sent resistors in the circuit and the speed of the music played can also be controlled.
The proposed circuit is based on IC 555 and IC 4017; it has two IC 555s and one IC 4017. It can generate 10 different tones and the frequency of each tone can be controlled by adjusting the pre-set resistors.
The speed of the tone which is played can be controlled by adjusting a separate pre-set resistor which is dedicated for controlling clock speed of IC1 555.
The IC1 generates clock signal which is fed to IC 4017’s clock input pin. The IC3 generates tone and fed to 8 ohm through a 100uF capacitor for block DC signals.
The IC3 generates different tones anywhere between few hundred hertz to few kilohertz. When different frequencies are generated with some interval, it resembles as music.
By adjusting the 10 pre-set resistors at different levels properly we can generate melodious tone from the circuit. IC 4017 is decade counter; each pulse from the IC1 555 turns one of 10 output pin to high and rest of the pins to low sequentially.
The pin which is high passes voltage through its connected pre-set resistor, due to its resistance the voltage passing to IC3 555 changes whichgenerates frequency depending on the pre-set resistor value.
The ten diodes which are connected on all 10 output pins of IC 4017 prevent current passing to other output pins while one of the pins is high.
The speed of IC 4017 which turn one of the pin to high sequentially and rest of the pins to low, depend on IC1 555, so by adjusting VR1 we can control the speed of the tone for this programmable musical organ circuit.