Can any one give me the technical details of a musical greeting card? :shock:

 

This is how I see it (then it's gotta be that way :lol: )

There's a microprocessor inside, with a ROM that contains the melody. There's a buzzer that reproduces that melody. There are several ways to do that, but I guess the easiest would be PWM (Pulse Width Modulation). The buzzer is turned On and Off using a squarewave, but since it's duty cycle changes all the time, the actual sound from the buzzer is different (kindda approximation of a sinewave with a squarewave).

Another way would be to have a ROM with melody and a shift-register that will read that memory and send ones and zeros to the buzzer.

I don't think that you can modify one (to add your melody), since it's all inside 1 chip, that chip is unknown, it's programmed during fabrication process (the ready-made program with music is put inside, rather than programming every chip afterwards) and the memory inside is Read-Only.

You could build one actually, with a PIC microprocessor. Check out this website, really interesting:

http://centauri.ezy.net.au/~fastvid/picsound.htm

You could use one of those small, 8-pin pics for that (12f series). And if you go with SOIC, then the design will be even smaller.

Good Luck,
TI|CP

 

and i found out that by shortning the contacts u can access different tunes... :lol:

 

I didn't know about that... Thanks...

That means that they just burn the IC with several tunes and then just connect the pins together, according to what they want it to output.

 

UM 66 is an IC with a burnt in song of 64 notes or so....

It has an inbuilt oscillator and all it needs is a pezo speaker and a Vcc...

It is a 3 pin IC looks like an bc548 transistor. I guess the UM xx series shall have a different music for each xx number. UM66 was "jingle bell" if I remember it right.

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Bharath Bhushan Lohray.
M.Sc. Electronics.