UM66 Melody Generator – First Step for Electronics Hobbyists
UM66 is a melody generating IC commonly used in calling bell, phone, toys, musical bell in doors, home security alarm systems, burglar alarms etc. It is a three pin IC looks like a transistor. Its first pin is ground, second is VCC and the third is the melody output. Supply voltage that can be given to the IC is in the range of 1.5V- 4.5V. These are CMOS ICs and have very small power consumption. Melody generator will reset when the power is turned on and then the melody begins from the first note.
The melody generator has an inbuilt beat and tone generator. The time base for beat and tone generator is an inbuilt oscillator. Tone generator and beat generator are programmed divider. Tone generator produces certain frequency. These frequencies are a factor of the oscillator frequency. Beat generator contains 15 available beats. Of these four beats can be selected. It has a 62 notes ROM to play music. A set of 4 bits controls the scale code while 2 bits control the rhythm code.
Many versions of UM66 are available to generate tones of different songs, for eg. UM66T01 generates tone for songs ‘Jingle bells’, ‘Santa Claus is coming to town’ and ‘We wish you a merry X’mas’, UTC UM66T05L for ‘ Home sweet home’, UTC UM66T19L for ‘ For Alice,’ UTC UM66T32L for ‘COO COO waltz’ and UTC UM66T68L ‘It is a small world’.
.The supply input to the IC should not exceed 4.5V. Otherwise it may damage the IC. So if we want to combine this circuit with some other circuit having VCC greater than 4.5V then use zener diode voltage regulator.
The following diagram shows the working of UM66 as a musical IC.
Wiring in breadboard,
In this zener diode voltage regulator is used. This will maintain the required supply voltage less than 4.5 while combining with other circuits. Here zener diode with a breakdown voltage of 3.3V is used. This will maintain output voltage nearer to 3.3V for a wide range of reverse current. Supply input (pin 2) of the UM66 is given to the regulator output. Melody output is taken from pin3. This output is lower in amplitude and cannot drive a loudspeaker. Thus an NPN transistor is used for amplification. Output of the melody generator is given to the BC547 NPN transistor through 1K resistor for limiting the current. Amplified output is given to the loudspeaker.
Note : You can use a low power speaker like 8Ω, 0.5W.
Want to See Output ?
You can download the pdf files of PCB at the bottom of this article.
Here is the one made in our lab.
You can download the PDF of PCBs here. Please note that it is a zipped folder, so you need to unzip it.