Application of the multi-instrument melody generator IC UM3481A
Application of the pre-programmed Hindi melody generator IC WR630173
Use of DIP switches for case-selection
The Multi-Melody Generator is a versatile melody generator which is capable of generating various English and Hindi version melodies using UM3481A (multi-instrument melody generator IC) and WR630173 (pre-programmed Hindi melody generator). Instrumental effects can also be produced with the same circuit.The advantage of this circuit lies in its ability to select various modes of melodies through DIP switches, ability to generate instrumental effect and volume control mechanism.
The Multi Melody Generator circuit is powered by a 3V battery. A switch (S2) is the main input-select switch for producing different tones in the loudspeaker. Various modes of operation can be selected through DIP switches S3, S4 and S5 connected to pins 3, 5 and 7 of UM3481A (IC1), respectively. Pin 7 is the envelope circuit terminal through which instrumental effects are produced. The preamplifier outputs are available at pins 10 and 11, which are fed to loudspeaker, driver transistors T1 (SK100) and T2 (SL100), respectively.
When the circuit is switched on by closing switch S1, LED1 glows. When DIP switches S3 and S5 are closed and S4 is open; and switch S2 is pressed, a melody is generated through the loudspeaker. (The potentiometer VR1 is provided for volume control in the circuit). Pressing the switch S2 again generates a new melodious tone. If switches S3 and S4 are opened while S5 is closed, the same tone keeps repeating for every press of switch S2. When switch S5 is open, an instrumental effect is generated from the loudspeaker. This effect is produced by the enveloping circuit consisting of capacitor C1 and resistor R2 connected to pin 7 of IC1. Only C1 or R2 or its parallel combination can be used to generate a distinct instrument effect. To select any of these options, two jumper terminals J1 and J2 are provided in the circuit at C1 and R2, respectively. For example, if you want to use only C1, you can join J1 terminals using hookup wire or jumper cap and keep J2 open. The repetition of the musical effect depends on the status of switches S3 and S4.
The oscillation frequency is produced by the resistor and capacitor connected at pins 14 and 13 of IC1. This frequency is used as a time base for the tone, rhythm and tempo generators. The quality of the melody tones depends on this frequency. Resistor R6 (100-kilo-ohm) connected to pin 15 makes the circuit insensitive to variations in the power supply.
