The M348X series is a mask-ROM-programmed multi-instrument melody generator , implemented by CMOS technology. It is designed to play the melody according to the previously programmed information. The device also includes a pre-amplifier which provides a simple interface to the driver circuit. The M348X series is intended for applications such as toys, door bells, music box, melody clock/timers and telephones.
This project based on the M348X IC is the electronic equivalent of a mechanical music box. It has a range of tunes and is activated by light falling on a light dependent resistor (LDR) sensor. It can be placed anywhere that you want a tune to play when light falls on it: a cupboard, music box. There could be some applications where the LDR is replaced by a switch or a push-button.
Christmas music is available when M3481 is used.
Jingle Bells
Santa Claus Is Coming To Town
Silent Night, Holy Night
Joy To The World
Rudolph, The Red-nosed Reindeer
We Wish You A Merry Christmas
O Come, All Ye Faithful
Hark, The Herald Angels Sing
The following music is available when M3485 is used.
The Hawaiian Wedding Song
Try To Remember
Aloha OE
Butterfly Love Story
Yesterday
Melody Music Generation Description
When light falls on the LDR, the music IC is enabled by the positive potential appearing on pin 2. The sensitivity of the LDR can be changed by varying the value of the 100K in the SIL connected to pin 2. A tune is selected by pushing the PCB-mounted tact switch. The jumper J1 determines whether the selected tune will play continuously or will cycle through all the tunes available in the IC. The musical pitch is determined by the resistor R1. Decreasing the value of R1 lowers the pitch, and each tune takes longer to play. The RC network at pin 7 shapes the sound. The speaker is driven by a complementary pair of transistors driven by the IC. Negative feedback is provided by R3 to stabilise the DC voltage at the emitters of Q1 & Q2.
Jumper J2 selects whether or not a tune stops immediately when light is removed from the LDR, or it plays right through to its end before stopping. In the idle state the circuit draws about 50uA, and about 20mA when it is operating. Therefore, there is no need for an off/on switch.
Melody Music Parts List
The parts list for the project is as shown below.
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