LED Strobe Light Circuit with Chasing, Flashing Effects

The proposed LED strobe light circuit will not only flash a group of LEDs with strobe pulses, but will also create a sequentially chasing effect over the strobing LEDs.

You might be quite familiar with colorful LED strobe lights, and should have seen them pretty commonly in parties and discotheques.

Let's see how we can make one such circuit at home using LEDs. Although these devices use laser light a for the generation of the required strobe effect, using high bright LEDs can also be a good alternative, if many of are included.

Here I have explained a very simple yet very effective LED strobe light circuit which is in fact more innovative than its commercial counterparts as it produces a chasing effect to lights while implementing the strobing flashing effect simultaneously.

Circuit Operation:

The proposed LED strobe light circuit is highly innovative and versatile, it actually can be used in many different applications, like in toys, decoration items, as party lights, and in avionics for displaying warning signals from the airplane (tail light probably).

The circuit utilizes the popular IC 4017 for generating the basic chasing or sequencing output through its outputs.

However the above chasing effect becomes a very primary application of the IC and here we are not looking for just a chasing effect, rather we are interested in the strobing pattern which is induced in the circuit by forcing the outputs of the 4017 IC to flash or blink rapidly as it sequences the lights.

To make the IC output strobe, we introduce another IC 4049 and integrate it to the LEDs in the circuit.

The IC 4049 basically consists of 6 NOT gate. Here two of them are used and configured as an oscillator.

Two of the gates are used buffers for facilitating better grounding effect to the LEDs, while the remaining two are used as another oscillator for driving the IC 4017 clock input.

The strobing oscillator and the clocking oscillator can be varied discretely through the respective pots for creating user defined intriguing LED strobe effects.

The LEDs common cathode termination is not connected to its usual position, i.e. to the ground; rather it’s connected to the output of the buffer NOT gates.

The oscillator from the 4049 IC transmits; rapid high and low logic pulses to the buffers which carry forward the response to the LED cathode.

When the buffer out is high the LEDs remain shut off during that instant. However the moment the buffer outputs go low, the LEDs light up and flash rapidly while sequencing, as the LED cathodes now find the ground path through the buffer low output.

The following figure shows the complete LED strobe light circuit diagram with chasing effect enhanced with a synchronized flashing effect.

 Circuit Diagram

Parts List

Calculations:

Frequency of Oscillation:

The frequency of oscillation for the 4093 IC NAND gate RC oscillator is given by the formula:

f = 1 / (1.4 * R * C) Where:

f = Frequency of oscillation (in Hz)

R = Resistor value (in ohms) (VR₁ + R₁ or VR₂ + R₂)

C = Capacitor value (in farads) (C₁ or C₂)

Duty Cycle (for non-symmetrical configurations):

The duty cycle which determines the percentage of time the signal remains HIGH is given by the formula:

Duty Cycle = (R₁ / (R₁ + R₂)) * 100

Where:

R₁ = Resistor controlling the charging time of the capacitor

R₂ = Resistor controlling the discharging time of the capacitor

For a symmetrical configuration where the same resistor and capacitor are used for both charging and discharging the duty cycle is close to 50%.

Example Calculation:

Suppose the following values are used:

R = 10 kΩ (10,000 ohms)

C = 0.1 µF (0.1 * 10^-6 farads)

Substitute these values into the formula for frequency:

f = 1 / (1.4 * R * C)

f = 1 / (1.4 * 10,000 * 0.1 * 10^-6)

f = 1 / (1.4 * 10^-3)

f = 1 / 0.0014 f ≈ 714 Hz

So, the frequency of oscillation is approximately 714 Hz.

Adjusting Frequency: To increase the frequency you can decrease the value of either R or C. So, to decrease the frequency increase the value of either R or C.

IC 555 Strobe Light Circuit

The following inquiry  for making a single IC Strobe light circuit was sent to me by one of the keen readers of this blog, using the concept of IC 555 based LED strobe light effect generator circuit, I have explained the whole issue.

Technical Specifications

Thanks for this guide, I went by my local radio shack and picked up most of these components...Two
things I was not able to acquire was a 1m pot (all they had was a giant
sized pot in the 1m rating) and a 100k resistor (they were out)

I picked up a 4 pack of 22k resistors and wired them in series which gave me 88k which again is close.

I also picked up two 100k pots which i hoped could prove useful.

Knowing full well I don't have the recommended materials on the list I got an effect which didn't much resemble a strobe.

Using the 100k pot there is some variance in the flash speed but it isn't really slow to really fast.

Also my led never goes all the way out using this, again possibly my fault for having the wrong components.

Circuit Objective

What I would like: the ability to strobe a LED three or 4 sharp fast pulses with a pause between bursts

What will the difference between 88k ohms and 100k ohms in the resistor be visually?
I assume a 1m pot will give a much wider range of speed adjustment.

To get pulses with the led do I need an oscillator? with another pot?

Thanks in advance!

Solving the Circuit Objective

Thanks for replying.

I think the above circuit is not very suitable for obtaining strobe light effects, because it is not designed for generating differentiated mark and space ratios.

Your requirement of making the pulses pause for a moment in between sharp pulses would require a PWM kind of design with the IC 555.

A conventional type of PWM generator using a IC 555 is shown below and can be hopefully used for your type of application.

Here the pot can be used of discretely adjusting the mark/space ratio of the output pulses which in turn helps to optimize the output for obtaining the intended sharp pulses and pauses, this dimensioned output ultimately produces the required strobe effects with the connected LEDs.

IC 555 Strobe Light Circuit Diagram

Video Demonstration

Calculations:

Frequency of Oscillation:

f = 1.44 / ((R₁ + 2 * R₂) * C)

Where:

f = Frequency of oscillation (in Hz)

R₁ = Fixed resistor (100 kΩ)

R₂ = Variable resistor (potentiometer)

C = Capacitor (1 µF)

Duty Cycle:

Duty Cycle = ((R₁ + R_charging) / (R₁ + R_charging + R_discharging)) * 100

Where:

R_charging = Resistance in the charging path (adjusted by the potentiometer)

R_discharging = Resistance in the discharging path (also adjusted by the potentiometer)

Example Calculation:

Assume we have the following values in hand:

R₁ = 100 kΩ

R₂ = Potentiometer adjustable between 1 kΩ and 100 kΩ

C = 1 µF

For R₂ = 10 kΩ:

f = 1.44 / ((100,000 + 2 * 10,000) * 1 * 10^-6)

f = 1.44 / (120,000 * 10^-6)

f = 1.44 / 0.12

f = 12 Hz

For R2 = 100 kΩ:

f = 1.44 / ((100,000 + 2 * 100,000) * 1 * 10^-6)

f = 1.44 / (300,000 * 10^-6)

f = 1.44 / 0.3

f = 4.8 Hz

So the frequency will vary between 4.8 Hz and 12 Hz depending on R2.

For Duty Cycle:

If R_charging = R2 = 50 kΩ and R_discharging = R2 = 50 kΩ:

Duty Cycle = ((100,000 + 50,000) / (100,000 + 50,000 + 50,000)) * 100

Duty Cycle = (150,000 / 200,000) * 100

Duty Cycle = 75%

You can adjust R₂ to adjust the duty cycle can range from near 0% to close to 100%.