Christmas tree decoration

A little blinking ball like object for season's decorations.

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I saw the Circuit sculpture contest and looked into my boxes what I was having at hand. And close to the end of the year the idea was quite obvious.

Two wires in circular shape form the base of a ball-like object.
One of these circles serves as ground the other provides the supply voltage.

I built ordinary astable multivibrators. One with 100k and 47uF, the other with 180k and 33uF to have slightly different blinking frequencies. In each of these two independent circuits three LEDs and a 100 Ohm resistor are wired in series.

The coin cell holder is also bent from wire and soldered to  small piece of PCB (comprising just three holes) for stability reasons. I added a two pin male connector and a jumper as switch. 

To facilitate soldering I used hot glue to put the circles in place. When everything was finished I removed the glue and connected the wire ends of each circle with a short piece of grey cable isolation for stability and to avoid shorts.

MPEG-4 Video - 33.26 MB - 12/19/2018 at 19:31


  • 12 × LED red, transparent housing, 3mm
  • 4 × 100 Ohm
  • 4 × BC 546 or similar
  • 2 × 100k Ohm
  • 2 × 47uF

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  • 1

    Some details about building it. The decoration uses two independent astable multivibrators. I was thinking about using 555 based circuits but I thought to go really with just the basics would be nicer.

  • 2
    The circuit:
  • 3
    Choice of R and C:

    in one of the circuits I use R=100k and C=47uF. In the other R=180k and C=33uF. The choices are rather arbitrary. They are mostly due to what I had lying around and I wanted to have time periods close to one another but not the same. The periods are roughly 3.2s for the first combination and 4.1s for the second one.

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MaBe42 wrote 12/22/2018 at 13:19 point

Thanks. I was also considering the 555 at first. But it would require about the some number of components. So I went for the very basic design. I just added the schematic and some building instructions. I will add some details about the battery holder, later. Probably not before next week.

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Dr. Cockroach wrote 12/21/2018 at 20:46 point

I second that and also like the use of transistors instead of 555 timers or the like :-) As soon as you said two astables, I knew in my head how you wired it :-)

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Mike Szczys wrote 12/21/2018 at 19:36 point

Cool! I like the astable multivibrator approach since combining two of them with different periods results in the appearance of four different animation types. It'd be great to look at a schematic if you have one (the picture of a hand-written one would be fine by me ;-D )

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