06-05-2011, 12:21 PM
This melody generator can generatevarious English and Hinditunes as also instrumental effects.Various modes of melodies canbe selected through DIP switches.Other advantages are high volume andvolume control.IC UM3481A is a 16-pin multiinstrumentmelody generator. It isa mask-ROM-programmed IC designedto play the melody accordingto the programmed data. Its inbuiltpreamplifier provides a simple interfaceto the driver circuit. The IC canbe replaced with other UM348XXXseries, WR630173 or WE4822 melodygenerator ICs. A WR630173 preprogrammedas Hindi melody generatorcan be used here.There are 16 tunesstored in WR630173including mera jootahai japani, mera naamchin chin chu, hare ramahare krishna, raghu patiraghav raja ram andramaiya vasta vaiya.The circuit is poweredby a 3V battery.Switch S2 is the maininput-select switch for producing differenttones in the loudspeaker. Variousmodes of operation are selectedthrough DIP switches S3, S4 and S5connected to pins 3, 5 and 7 of IC1, respectively.Pin 7 is the envelope circuitterminal through which instrumentaleffects are produced. The preamplifieroutputs are available at pins 10 and 11,which are fed to loudspeaker-drivertransistors T1 (SK100) and T2 (SL100),respectively.When you switch on the circuitby closing switch S1, LED1 glows.If DIP switches S3 and S5 are closedand S4 open, pressing input switch S2will generate a melody tone from theloudspeaker. Vary VR1 to adjust itsvolume. Pressing S2 again will generatea new melody tone. If switches S3and S4 are opened while S5 is closed,the same tone keeps repeating forevery pressing of S2. The positions ofDIP switches and the various modesof melodies are summarised in thetable.When switch S5 is open, it willgenerate an instrumental effectfrom the loudspeaker. This effect isproduced by the enveloping circuitconsisting of capacitor C1 and resistorR2 connected to pin 7 of IC1. In fact,by hit and trial you can choose thevalues of these components as peryour taste by listening to the outputsound. Only C1 or R2 or its parallelcombination can be used to generatea distinct instrument effect. To selectany of these options, two jumperterminals J1 and J2 are provided inthe circuit at C1 and R2, respectively.For example, if you want to use onlyC1, you can join J1 terminals usinghookup wire or jumper cap and keepJ2 open. The repetition of the musicaleffect depends on the status ofswitches S3 and S4.The oscillation frequency is producedby the resistor and capacitorconnected at pins 14 and 13 of IC1. Thisfrequency is used as a time base forthe tone, rhythm and tempo generators.The quality of the melody tonesdepends on this frequency. ResistorR6 (100-kilo-ohm) connected to pin 15makes the circuit insensitive to variationsin the power supply.
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http://kitsnsparesadmin/pdffiles/Melody%...effect.pdf