A very interesting musical Christmas decoration light circuit can be built using a single IC, and some other few passive components, let’s learn the details as furnished below.

By: Ritu Panday

How it Works

The circuit of a selectable muti-musical song player with 5 sequential light pattern generator is discussed here using just a single chip M668, and a few resistors and BJTs. The sequential light control also exhibits multiple patterns depending on the pressing of a button, and this is executed through 5nos of SCRs and lamps.

The lamps are in the form single 10 watt filament bulbs or even colored 1 watt LED bulbs might work beautifully for this application.



Referring to the diagram the IC M668 may have 25 different Christmas melodies or songs embedded in it, which is played randomly as long as the circuit is powered.

Additionally the button TG can be pressed anytime for changing the song number, and playing any other desired number on the connected loudspeaker.

The loudspeaker is a tiny 32 ohms speaker, which is driven by a BJT amplifier capable of producing an adequate ½ watt power over the speaker which may be quite enough for anybody to listen to the melodies within the premise.

The VOL button can be used for adjusting the volume as per individual preference and tolerance.

The best thing about this musical Christmas light sequencer circuit is not only its dual function feature of music and light generation but also its transformerless compact design.

The power for this decoration light circuit can be directly acquired from the AC mains through a little transformerless power supply circuit comprising of some diodes and capacitors as shown below:


Mains Power Supply Connection Details





As can be seen , direct AC mains Vdd1 is used for powering the AC lamps, therefore make sure the connected lamps are rated at 120V AC, or 220CV AC and not anything less than that.

Vdd is used for powering the IC based circuit and is therefore stabilized to 12V, however care must be taken not to touch the circuit while it's powered because this musical Christmas light decoration circuit is absolutely NOT isolated from mains, and therefore is life threatening in open condition.

This implies that the whole circuit must be enclosed inside a suitable enclosure with only the mains cord terminating for AC plug in.

The lights could be terminated through wire and bulb holder arrangement and here too care should be taken to perfectly insulate the individual bulb strings and holders so that no accidental shocks are encountered while decorating the lights over a Christmas tree or any similar desired position.

The following image provides the list of songs that the IC M668 may have embedded in it:



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