A doorbell is a signalling device typically placed near a door to a building’s entrance. When a visitor presses a button the bell rings inside the building, alerting the occupant to the presence of the visitor. Here we present a simple and cost effective door bell circuit based on IC 8021-2 from Formox Semiconductors. It is an 8-pin DIP IC whose only four pins, as shown in the circuit, have been used. It can be easily set up in your house just-in-case.
Door bell circuit
The IC has an in-built circuitry to produce ding-dong sound each time its pin 3 is pulled low. The sound is stored in the IC as bits, as in a ROM. The sound output from the IC can’t however drive a speaker directly, as this puts strain on the device. Therefore a complementary pair, two-transistor amplifier is used to amplify the sound to a fair level of audibility. You may either use a piezo tweeter or an 8-ohm, 500mW speaker at the output.
During the standby period, the IC consumes nominal current of a few microamperes only. Therefore switch S1 may be kept closed. Each time 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 produced, it has no effect whatever and the two ding-dong bell sounds will be invariably produced.
The article was first published in March 2002 and has recently been updated.
where the spare IC is availble?
The 8021 IC used here is an old IC. You can find a similar project titled “Ding Dong Touch Bell” published in the February 2013 issue which uses a more recent IC easily available online.
IC 8021-2 not available, if you can send or give local alternate substitute with circuit to make ding dong or church bell kit. If kit available ill purchase it.