But, I think one of the easiest way, at least in terms of the “easiness” of building the circuit, is using a 555 timer.
The 555 timer is a chip that you can use for creating a signal that turns on and off repeatedly. That’s exactly what you need for blinking Christmas lights!
Just connect this signal to some LEDs and a resistor to control the LED currents.
Blinking Christmas Light Circuit Diagram
In this circuit you’ll only need 4 components + the LEDs and the resistor.
To get the blinking effect, you need to set the 555 Timer in astable mode. Then it’s output will change between 9V and 0V repeatedly.
Here’s the full circuit (see further down for parts list and explanation):
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Parts List
Part
Value
Description
U1
LM555
555 timer
C1
4.7 µF (10V and upwards)
Capacitor
R1
10k Ohm
Resistor
R2
100k Ohm
Resistor
R3
68 Ohm
Resistor
L1 – L8
Standard Output LED
Light-Emitting Diode
Setting The Blinking Speed
Two resistors and a capacitor is all you need to set the blinking speed. You can calculate the number of “blinks” per second with this formula:
But, an even easier way is to use this calculator. Then you can try with whatever values you have at home and see what result you can expect.
With the values I’ve chosen, you should get about 1.5 blinks per second. And the time the LEDs are on should be about the same as the time they are off.
Setting The LED Brightness
When you light up an LED you should always use a resistor, so that you can control how much current that goes through it.
10-15 mA is usually a good current amount for standard output LEDs. In this circuit, you have eight of these in parallel. That means you need 80-120 mA in total for the eight LEDs. Which also means you want this much current to flow through the resistor. The current going through the resistor will be the amount of current that will be shared among the LEDs.
The LEDs I used had a forward voltage of about 2V. So, a 68 Ohm resistor is a good match. You can learn how to calculate the correct resistor value for any LED in my article about current limiting resistors.
If you’re thinking about adding more LEDs, keep in mind that the 555 timer only supports around 200 mA of current. For example 20 LEDs with 10 mA.
Soldering the LEDs
I used a cable from some old headphones to connect the LEDs. Then I used heat shrink tube to cover up the solder joints.
My Blinking Christmas Lights
If you built this circuit, let me know in the comment field below. Also, any questions about modifications or anything, use the comment field below.