Simple LED Chaser Circuit using CD4017 and NE555 IC

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Introduction:

An LED chaser circuit is a popular electronics project that creates a sequential blinking pattern of LEDs, often resembling running lights. The key components of this circuit are the CD4017 Decade Counter IC and the NE555 Timer IC.

The NE555 functions as a stable pulse generator (astable mode), producing clock pulses at a consistent frequency. These pulses are fed into the CD4017 IC, which is responsible for controlling the LEDs. The CD4017 is a decade counter that has 10 output pins, each corresponding to a different LED. With each clock pulse from the NE555, the CD4017 shifts its output from one pin to the next, lighting the LEDs in a sequential pattern.

By adjusting the frequency of the NE555's output, the speed of the LED sequence can be controlled. This circuit is often used in decorative lighting or as a visual indicator in electronics projects. The simplicity of the components makes it an ideal beginner-level project for learning about counters and timers.

Component Details

  • IC CD4017, NE555
  • Resistor 10K ohm, 220 ohm
  • Variable Resistor 10K ohm 
  • Capacitor  10nf, 10uf 
  • LED  any Color 
  • Battery 9V

Pinout of CD4017 IC:



The CD4017 is a widely used decade counter IC that can count from 0 to 9 (10 outputs). It’s often used in LED sequencing, light chasers, and other projects requiring sequential switching. It is based on CMOS technology, which ensures low power consumption and wide voltage range operation (from 3V to 15V). The IC takes clock pulses and outputs a HIGH signal at one of its 10 output pins in a sequential manner with each pulse.

  • Pin 1-7, 9-11 (Q0 to Q9): These are the 10 output pins that sequentially go HIGH as the counter progresses from 0 to 9.
  • Pin 8 (GND): Ground pin, connected to the negative terminal of the power supply.
  • Pin 12 (Carry Out): Outputs a pulse every 10 counts, useful for cascading multiple CD4017 ICs.
  • Pin 13 (Enable/Clock Inhibit): When HIGH, the counter is paused. When LOW, it allows the counter to count pulses.
  • Pin 14 (Clock): Input pin where the clock pulses are applied to control the counting process.
  • Pin 15 (Reset): Resets the count back to 0 when a HIGH signal is applied.
  • Pin 16 (Vcc): Connected to the positive terminal of the power supply

Pinout Of NE555 Time IC:

The NE555 is a highly versatile timer IC used in various timing, delay, pulse generation, and oscillator applications. It can operate in three modes: astable (free-running oscillator), monostable (one-shot pulse), and bistable (flip-flop). In astable mode, it generates a continuous square wave output, making it ideal for use in LED flashers and chaser circuits. The NE555 operates on a wide voltage range (from 4.5V to 15V), making it suitable for both low- and high-power applications

  1. .Pin 1 (Ground): Connected to the negative terminal of the power supply.
  2. Pin 2 (Trigger): When the voltage drops below 1/3 of the supply voltage, the output goes HIGH. This is typically used to start a timing cycle.
  3. Pin 3 (Output): Outputs the waveform. It can source or sink up to 200mA of current, enough to drive LEDs directly.
  4. Pin 4 (Reset): Resets the timer. Normally connected to the positive supply to avoid accidental resets.
  5. Pin 5 (Control Voltage): Modifies the threshold and trigger voltages. Often left unconnected or grounded through a capacitor for stability.
  6. Pin 6 (Threshold): Monitors the voltage and resets the output to LOW when it exceeds 2/3 of the supply voltage.
  7. Pin 7 (Discharge): Connected to the timing capacitor and discharges it when the output is LOW.
  8. Pin 8 (Vcc): Connected to the positive terminal of the power supply.

Circuit Diagram:

Components:

  1. NE555 Timer IC: This is configured in astable mode to generate clock pulses.
  2. CD4017 Decade Counter IC: It takes clock pulses from the 555 timer and sequentially turns on each LED.
  3. Resistors and Capacitors:
    • R11 (10K) and RP1 (10K potentiometer): Used to control the frequency of the pulses from the 555 timer.
    • C1 (10 µF) and C2 (10 nF): These capacitors are used to stabilize the timer's output and help set the frequency.
    • R1 to R10 (220 ohms each): Limit the current going to each LED.
  4. LEDs (LED1 to LED10): These are the output indicators that will light up sequentially.

Working:

  • The 555 timer generates continuous clock pulses, the speed of which can be adjusted using the 10K potentiometer (RP1).
  • The output from pin 3 of the 555 timer goes to the clock input (pin 14) of the CD4017 IC.
  • The CD4017 counts the clock pulses and sends a high signal to its output pins (pins 3, 2, 4, 7, 10, 1, 5, 6, 9, 11) one after the other, lighting up the LEDs in sequence.
  • Each LED is connected to an output pin through a current-limiting resistor (220 ohms), which ensures that the LEDs don’t receive too much current.

Applications & Uses:

  1. Decorative Lighting: Used in decorative displays, including Christmas lights and stage lighting, where sequential lighting effects are desired.
  2. Signage: Commonly used in advertising boards and signs to attract attention with moving lights.
  3. Running Lights: Automotive applications, such as sequential turn signal indicators or decorative running lights.
  4. Learning and Education: Ideal for teaching basic electronics, logic circuits, and timing concepts.

 

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