Description

Here we present a simple an low cost ding dong bell suitable for calling bell purposes.It is made around IC 8021-2 .It is a 8 pin IC but only four pins are shown here. 8021 has an in-built circuitry to produce ding dong sound each time its pin 3 is pulled low.The sound is stored in a 4 bit ROM.a complementary-pair, two-transistor amplifier is used to amplify the sound to a fair level of audibility.A piezo
tweeter or an 8-ohm, 500mW speaker can be used at the output.

Each time when switch S2 is pressed, ding dong sound is produced twice. If you try to press switch S2 a second time when the first ding dong sound is still being produed, it has no effect whatever and the two ding-dong bell sounds will be invariably produced.S1 is the ON- OFF switch.Assemble the circuit on a good quality all pupose PCB.Don’t forget to use an IC holder for IC 8021.

Circuit Diagram. Click to view larger.

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