Related Posts: Melody Generator using UM 66 Door Bell Circuit Using NE555
The main objective of the doorbell circuit is to convert electrical signals (input) into audio signals (output) with a single press of a switch.
The circuit given below is a modified version of the Melody Generator Circuit, whose link is given above. In the previous circuit you had to keep the switch manually pressed for making the IC play the full music.
Here if once the push button is pressed Capacitor C1 is charged and the transistor Q2 will keep the IC playing the music till it ends. The time for the IC to play depends on discharging time of C1 which can be set by R1. Set R1 to select your time, whether full tone or a part in one press. Transistor Q2 drives the speaker. Pin 1 of UM66 is connected to the base of Transistor Q1 (BC548), so as to amplify the signal to drive the 8 Ohms speaker (K1).
The IC UM66 is a melody generator CMOS IC and can be found in sound generating objects like doorbells, musical toys for kids, telephones, intruder alarms and so on. The IC has 3 pins with terminals GND (1), Vcc (2) & Melody Output (3). The tones are generated by the corresponding electrical signals at Pin 3. The IC works on a supply voltage range of (1.5-4.5) Volts. This IC can be used in small circuits as it consumes very less power. The IC will reset after a tone is played, and will start playing from the beginning. All you have to do is reset the IC using Switch S1. The IC does not require any new components to generate the audio signals. IC has a beat & tone generator that is already built inside. The time base for it is an in-built oscillator.
The tone generator produces a particular frequency, that is the oscillator frequency factor. The beat generator has 15 different beats, out of which four of them can be selected. The tone is generated using a 62 notes ROM. Out of this 4 bits control the scale code and 2 bits are used for the rhythm code.
Different tones are available with different versions of the IC. Some common tones are “Jingle all the way”, “Santa Claus is coming to town”, and “Christmas song”.
Doorbell Circuit Diagram with Parts List
|S1||Push Button Switch|
|K1||8 Ohm Speaker|
|B1||3 Volt Battery|
- Do not give more than 4.5 V to UM 66.
- POT R2 is not necessary and can be bypassed. But if included you can set the loudness.
We have many other Tone Generator circuits that you may like take a look: