This blinking LED circuit uses only one IC, requires no
firmware, and can be modified almost without limit. It is an
excellent starting circuit for those wanting to create blinking LED
effects. With proper changes to the current-limiting resistors,
this circuit can run on 3 - 15 VDC, making it ideal for battery-powered
I cannot find the original page that started me using this
circuit. That page contained an excellent explanation of how this
circuit works and included info on determining blink rates and
patterns. You can find some of that information here, but
it's still not as good as the original page...
Refer to my Eagle schematic (PDF) here.
This circuit uses a single 4060B IC, which is a CMOS 14-stage binary
divider. Note that the 'B' is important; the 4060B device has
extra current capability, needed for driving the LEDs. Refer to
the Fairchild 4060 datasheet here.
Basically, R1, R2, and C2 form an oscillator, generating timing pulses
for the 4060. These pulses feed the 4060's internal chain of
dividers. The output of each divider is available on one of the
Qn pins. For example, the Q4 output
(pin 7) is the output from the 4th divider
and changes state at the original clock frequency divided by 2^4 or 16.
Each Q output is at either GND or VCC at any given moment, and the
outputs change between these states based on the oscillator frequency
and which output they are in the divider chain.
If you choose any two Q outputs, such as Q4 and Q6 in the schematic,
you will see that these two outputs can provide three different ways to
control an LED:
|LED is off
|LED conducts from Q6 to Q4 (LED2
|LED conducts from Q4 to Q6 (LED1
|LED is off
the LEDs are reverse-wired between the two outputs, you will never have
both of these LEDs on at the same time.
Now take this simple two-LED concept and start adding LEDs and
current-limiting resistors between other outputs. The behavior of
any one LED depends on the direction it is wired between outputs, the
original oscillator frequency, and the outputs you use.
I have had 40 LEDs of various colors wired to a single 4060 IC and the
resulting pattern is simply beautiful! Note that it can take many
minutes for the pattern to repeat; unless you have a very long
attention span, the pattern will look random to you.
Experiment with different colored LEDs in your design. For
example, you could use a red LED1 and a green LED2.
The LED brightness will be a function of the voltage you provide and
the value of the current-limiting resistor (R3). The value of 180
ohms shown here should work for most LEDs using a voltage of 3 to 6
VDC. LED brightness is also a function of the LEDs you use; try
to get some of the high-brightness devices to get more punch for your
What current-limiting resistor?
The picture above shows a version of this circuit I built
to run on 12 VDC. Here I used a string of LEDs in place of the
single LED1 or LED2. The trick is to add the forward voltages of
the LEDs in the string, trying to get as close to 12 VDC total as
possible. For example, the forward voltage of red LEDs is 2 VDC,
so I used a string of six red LEDs in place of LED1 or LED2.
Similarly, I used strings of four blue, four green, or five yellow
LEDs. Since the total forward voltage for each string is nearly
equal to the power supply I used, I simply eliminated the
current-limiting resistor and wired the series strings directly to the
two outputs I chose.