MUSICAL GREETING CARDS

[Bri.Remya]

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

 

[theimperia]

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:

**broken link removed**

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

 

[RubberDucky]

I played with one in my early days

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

 

[theimperia]

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.

 

[lord loh.]

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.