Mini Christmas Tree

Idea: Elektor Lab

Are you already experiencing a bit of Christmas fatigue? If so, it is likely thanks (at least in part) to an overdose of Christmas carols on the radio and so on. Anyway, we have one last "Christmas" circuit for you. We aren't presenting anything out of the ordinary, other than the remarkable clock generator. Check out Figure 1.


Mini Christmas tree circuit
Figure 1

As you can see, the circuit consists of a CMOS decade counter (the 4017) and 10 LEDs plus series resistors. The Q outputs of the 4017 become active while the counter counts from 0 to 9. As soon as the counter reaches the position '10' (output Q9 then becomes high), the counter is reset because Q9 is connected to the reset input.

To be able to count, the 4017 needs a clock signal. Normally, that signal is provided by a clock generator. Here we do that in a somewhat unconventional way. LED D1 is a (orange) flashing LED. This means that its anode has an alternating high and low level, depending on whether the LED is off or on. And that alternating signal level can be used as a clock signal for the 4017 decade counter!

There is nothing else to say about the circuit. You can easily build it on a breadboard and arrange the LEDs in a Christmas tree pattern. Of course, the orange flashing LED should appear at the top.

Enjoy this Christmas tree circuit! All that remains is to wish you a happy 2021!