Blinker Circuit: Applications, and How to Make One Using a 555 Timer IC

Have you thought about doing a project that involves light-emitting diodes turning on and off sequentially? Well, the good news is that you can pull it off quickly. All you need is a blinker circuit. Also, you can use this circuit to create a programmed pattern of LEDs turning OFF and ON.

But to get the best results, you must construct the circuit accurately.

To make one, you can use a microcontroller, logic NOT-gate inverter, or 555 timer IC (our primary focus).

In this article, you’ll learn one of the best ways to construct this circuit, its applications, and more.

Let’s get started!  

Blinking LED Circuit Using a 555 Timer IC

We used the 555 timer IC because it’s pretty versatile. And it uses the resistor-capacitor network to create current pulses at certain time intervals.

As a result, the LED will not stay ON constantly. It will only come on when there’s a pulse and go OFF when it passes.

Interestingly, the process happens in a never-ending cycle, creating light flashes. Also, placing your timer chip in an astable mode is vital to get the best results.

That is, your IC should be in oscillator mode. In other words, your 555 timers should constantly switch between ON and OFF.

In addition, it’s possible to adjust the successive toggling. And you can make the adjustments using a potentiometer.

Here are the components you need:

• Many jumper wires

Jumper Wires

• Power supply – 9V battery

9V Battery

• Potentiometer (optional)

Potentiometer

• LED

LED strip

• Breadboard

BreadBoard

• 555 Timer IC

555 Timer IC chip

• R1 – 1KΩ (2)
• Relay module (optional)
• C1 – 10µF electrolytic capacitor
• R2 – 10KΩ
• C2  – 0.01µF ceramic capacitor

Diagram of the Circuit

In this circuit, you can use a DC power supply. But if you don’t have that, use the 9V battery. Also, the jumper wires will help to reduce the connection complication of the resistors and capacitors to the 555 timer chip.

In addition, the jumper wires help space out the circuit.

The circuit diagram shows that the electrolytic C1, R1, and R2 determine the rate at which the LED flashes. That said, the 555 timer produces square waves. And a square wave needs three essential time measurements.

First is the whole length of the square wave. That is when it’s high and low or the time is on and off. Second is the length of time that’s low and high (T_High and T_Low). The third is the square wave’s total time. And you can calculate it by adding the T_High and T_Low.

The duty cycle plays a significant role in the LED flasher circuit. And it’s because the duty cycle helps you to know the comparison between how long the LED stays on and off. So, if the square wave has a high time, it’s the duty cycle.

Hence, if you have a duty cycle of 30%, your LED will go off for 70% of the process and flash on for 30%.  

Calculation

You can  calculate your circuit’s value with the formula below:

1.T = 0.7 x (R1 + 2R2) C1 2. T_High = 0.7 x (R1 + R2) C1 3. T_Low = 0.7 x R2 x C1

The electrolytic capacitor charges via R1 and R2 but discharges only through R2. That’s why adding two resistor values is crucial to calculate T_High. But for the T_Low calculation, you can only use R2.

So, based on the formulas above, you’ll have longer cycles when you increase the resistor and capacitor values. But your values must be below to see your blinker circuit's flickering or flashing effect.

However, you also have to be careful because your values shouldn’t be too low. If this happens, your eyes may be unable to detect the flashing light. For instance, if your capacitor and resistance values are 0.1µF and 1KΩ, you’ll have a short ON-OFF cycle. Thus, your LED will be on constantly.

Consequently, your cycles will last for a few millionths of a second. That said, the values used in this circuit have a duty cycle of 50%. In other words, the LEDs will be on the same time they go off. So, it’s better to opt for a precise value range.

We can calculate T, T_High, and T_Low with the C1, R1, and R2 values.

1.  T = 0.7 x (1KΩ + 2(10KΩ)) x 10µF = 0.147 seconds

2. T_High = 0.7 x (1KΩ + 10KΩ) x 10µF = 0.077 seconds

3. T_Low = 0.7 x 1KΩ x 10µF = 0.07 seconds  

How Does the Circuit Work?

When the 555 timer IC’s Trigger Pin (Pin-2) perceives any voltage below 1/3^rd of the supply voltage, the LED will come ON. Also, the LED will go OFF when the 555 timer IC’s Threshold Pin (Pin-6) senses voltage above 2/3^rd of the supply voltage.

Further, when the LED is OFF, the 555 timer IC’s Discharge Pin (Pin-7) behaves like a negative rail. That is, the Discharge Pin connects to 0V internally.  

Improvements You Can Add to the Circuit

Add an extra transistor if you want a visually smoother ON and OFF transition. Then, drive the circuit from the voltage at the capacitor’s positive terminal.  

Blinking Two LEDs Using Transistors

Modify the circuit above if you want a course with two LED flashes. Consequently, your LEDs will take turns flashing. And the process happens pretty fast.

The components you need for this circuit include:

• Many jumper wires
• Power supply – 9V battery
• Potentiometer (optional)
• LED
• Breadboard
• 555 Timer IC
• R1 – 1KΩ (2)
• Relay module (optional)
• C1 – 10µF electrolytic capacitor
• R2 – 10KΩ
• C2  – 0.01µF ceramic capacitor
• Red LED (additional part)
• R3 – 1KΩ (additional component)

The components are the same as the first circuit, apart from the two extra features.

So, you can start by referring to the schematic circuit diagram.

With that, you can build the circuit. Your result should be like a police siren. The two-colored LEDs will take turns to flash at specified time intervals.  

Applications of The Blinker Circuit

• Cycles and vehicles (all types) – to turn the indicating courses.
• It works as an input for devices requiring timing pulses, like counter circuits that use 4026 IC. You can use the blinker circuit in the following applications:
• You can use the blinker circuit in SOS signaling circuits or Strobe lights, which helps signal a person who needs help or is in danger.
• In cars, as light indicators.
• You can use it to create a to and fro motion and control motor wipers.

Final Words

The blinker circuits combine semiconductor integrated circuits to turn LEDs ON and OFF. And the course can perform based on a programmed or sequential pattern.

So, it’s the perfect go-to if you’re dealing with projects that involve timing pulses, light indicators, etc.

You can make the blinker LED circuit with relays, microcontrollers, or inverters. But we focused more on the 555 timer IC in this article because of its versatility.

Do you need more details on building your circuit with different resistor and capacitor values? Or do you want to get the best blinker circuit for your project? Please feel free to reach ourPCB.