In this post we present two circuit ideas for creating Christmas tree decoration. The first idea explains a PCB mounted LED Christmas tree which blinks many LEDs in glittering manner imitating a small Christmas tree. The second designs describes a single IC random LED effect generator which can be installed over a real Christmas tree for decorating it with randomly blinking LED lights.
The circuit diagram for the Electronic LED Christmas Tree can be witnessed in the following figure. The circuit gets the power from two D batteries connected in series.
The circuit employs a couple of 7556 dual timers, U1 and U2, in order to accomplish the random pulsating light effect. Half of the section of each timer is utilized like an astable multivibrator (clock generator) configured to some other clock speed.
Slower LED flashing speed is selected to simulate the blinking light bulbs applied to actual Christmas trees. The flashing clock rates are set at 0.58, 1.02, 1.25, and 1.77 Hz. These 4 frequencies are transferred to the IC 74HC04 which is a hex inverter, IC U3.
You can find four inverter gates configured from this IC, which are U3a, U3b, U3e, and U3f. Each of these inverters get one of the inward clock signals from U1a, U1b, U2a, and U2b.
As soon as the inverter input becomes low, its output gets high, and when the inverter input gets high, its outputs gets low. Each inverter output is used for illuminating four LEDs arranged at the border of the PC, using random color LEDs for a glittering color effect.
The rest of the two CMOS inverters, U3c and U3d, are configured to illuminate the top LED. These gates are linked with each other through a "diode on" setup, therefore whenever one of those gates or both of those gates are high, causes current to pass across one particular or both of the 1N4148 diodes, D1 and D2, towards the upper LED, LED 9.
In this system the upper LED is shut off only while the two of those gates are low. In case a single gate is low and the other is high, the diode conducts; when the two gates are high, the diode becomes higher in intensity, triggering a rapidly blinking LED effect.
Troubleshooting
If the uppermost LED fails to illuminate correctly, examine the direction of the couple of 1N4148 diodes along with the polarity of the LED itself. Examine the direction of the other LEDs and check whether they too are illuminating or not.
If you find series of four LEDs not lighting up, trace the connections up to U3 and ensure that the IC 74HC04 stage gets the required clock signal. In case it is, the trouble can be possibly one of the LEDs and/or resistors, or the IC itself.
Do another inspection to check for shorts due to soldering jumps, before you consider the IC to be the main culprit. If you see a few of the LEDs are still failing to blink, return to the relevant portion of the timer stage and inspect the complementing parts.
To check if the 7556 timers are causing the issue, try swapping the ICs with one another. If you see the very same LEDs continue to be in the non-blinking state, you may deem the issue to be in the complementing circuitry. In case interchanging the 7556 ICs leads to one array of LEDs to start blinking and another array to remain shut off, only in such a situation it may be advisable to consider that the relevant timer ICs may be faulty.
PCB Design
The PCB design and the component overlay for the above explained LED Christmas tree can be found in the following images:
Random LED Flasher Circuit for Decorating a Christmas Tree
The next concept explains a simple random LED flasher circuit which can be used for decorating Christmas trees or other similar items during festivals.
How the Circuit Functions
I have already discussed a few interesting applications of the IC 4060 as an oscillator for driving clock input ICs like 4017 and also as a timer for producing variable time delays, ranging from a few seconds to many hours.
The oscillator function of the IC can also be effectively employed for driving colorful LEDs and for creating interesting LED light show. The idea can be used for illuminating vehicles, houses and typically Christmas trees during Christmas.
As discussed in one of my previous articles regarding the use of the IC as an oscillator, here the IC is set up as an oscillator for generating the required oscillations or clock signals at the different outputs.
Since the IC is able to generate clock signals or square waves through all its outputs, every output from the IC can be effectively used for displaying interesting LED light flashing with different rates of frequency.
The oscillations generated at the outputs of the IC increment with multiples of two or in other words they just double with their frequency across all the outputs at a specified pin out order.
Therefore some pin out LEDs may flash at very high rates while some may flash at very slow rates while still other may flash at intermediate rates, each LED chain having its own specific flashing rate.
The entire light show presented by the configuration thus creates an intriguing effect which can be very eye-catching.
The figure shows rather simple wiring where the IC itself acts as an oscillator as well as the LED driver.
Each of its output is wired into a string of colorful LEDs which may be set up or arranged in any desired format for acquiring the most interesting lighting effects.
The pot may be used for optimizing the flashing of the LEDs to the desired levels or at the rate which might suit the particular decorative application the most.
The circuit should be operated with voltages above 12 or precisely speaking, the applied voltage should be ideally fixed at 15 volts (regulated).
This typically high voltage enables many LEDs to be connected across each input, four to five LEDs to be exact.
Since so many LEDs are involved the power rating the transformer needs to be at least 500 mA.
The whole LED Christmas tree circuit may be enclosed inside a plastic box with strings of LEDs terminating out of the box so that they may attached to any desired structure like the Christmas tree.
I’m trying to get an Idea of how to make a 3-6v system of 5 randomized flashing White LEDs. I want them to be sporadic where more than 1 MAY be lit at a time, but no recognizable pattern exists. This would have to fit within an approximately 1″ x 2″ x 2″ space. What would be the simplest method for that?
You can build the 2nd design from this article
https://www.homemade-circuits.com/how-to-make-any-light-strobe-light/
It is a transistor astable. You will need 3 of these circuits, and put LEDs in series with R1 and R4 both. Then, you will get 6 LEDs that can be made to oscillate at different frequencies, as set by the respective C1, C2 values. This will simulate a random flashing effect across the LEDs
Thanks much. Do I need the BC 547’s or can I use some spare 3904 / 3906’s in their place?
Any general purpose NPN transistor will work. 2N3904 will also work
Hi Swagatam,
The above circuit shows 4 LEDs in series directly driven by the 4060 IC. Is this correct? Will the 4060 drive 4 LEDs in series without an external transistor? If they are Blue LEDs, what will be the current flowing through the 4060 with the 330R current limiting resistor (assuming a supply of 15V as your diagram shows)?I looked at an LED current limiting resistor calculator and it appears that the current of each LED would be 8ma. Will they be bright enough with only 8ma? I’m working on a project to flash 3 to four LEDs (depending on the color) in series from each output of the 4060 and I am using 12v supply. This circuit is very simple, but maybe I should consider transistors to get the power to drive the LEDs brightly. Your thoughts? Thanks!
Hi Norman, yes it will be bright enough for a 20 mA LED. Also, you can reduce the resistor values to 220 ohm to increase the brightness a little more.
If you want dazzling brightness then probably you may have to use an external transistor stage.
Can we increase the no.of led to 50 each
you will need transistor driver stages for that, on each channel.