Simple LED Chaser Circuit using IC 4017

This project makes a series of LEDs light up one by one like a chase.

It is a fun way to learn about electronics.

A special chip IC 555 creates a steady pulse.

This pulse tells another chip IC 4017 to turn its outputs on and off in a specific order.

Each output of the second chip is connected to an LED so, they light up in sequence.

You can adjust a knob to control how fast the LEDs chase each other.

The whole thing runs on a 12V battery.

This project is good for beginners because it teaches you about two important electronic parts and how they work together.

It is like a mini course in lighting up LEDs in sequence.

What is a LED Chaser Circuit using IC 4017:

A LED chaser circuit using the IC 4017 is a popular and simple electronic circuit that produces a visually appealing lighting effect by sequentially turning on and off a series of LEDs in a chasing pattern.

The IC 4017 also known as a decade counter is a versatile integrated circuit commonly used in sequential LED chaser circuits.

Circuit Operation:

Parts List:

Circuit working mentioned below:

The IC 555 is set up as an astable multivibrator, which means it continuously generates square wave pulses.

The potentiometer is connected between positive supply and ground and its wiper is connected to pin 6 of the IC 555.

This allows you to adjust the voltage at the 6 pin thereby controlling the frequency of the square wave output.

IC 4017 is a decade counter with 10 outputs pin 3 to pin 11.

The clock input pin 14 of IC 4017 is connected to the output pin 3 of the IC 555.

This means that the IC 4017 advances to the next output on each rising edge of the clock signal from the IC 555.

The 10 LEDs are connected to the outputs pin 3 to pin 11 of IC 4017.

As the clock signal is applied, the IC 4017 advances through its outputs activating each LED in sequence.

This creates the chasing or running light effect.

The potentiometer in the IC 555 circuit controls the speed of the clock signal.

By adjusting the potentiometer you can change the charging and discharging rates of the capacitor in the IC 555 circuit altering the frequency of the square wave output.

This, in turn changes the speed at which the LEDs sequence.

Circuit Functioning:

The IC 555 generates a continuous square wave clock signal whose frequency is adjustable with the potentiometer.

This clock signal is fed into the clock input of IC 4017causing it to sequentially activate its outputs.

Each output of IC 4017 is connected to an LED and as the outputs change, the LEDs light up in sequence, creating the LED chasing effect.

The entire circuit is powered by a 12V DC supply.

Speed Adjust:

By turning the potentiometer in the IC 555 circuit, you can control the speed at which the LEDs light up in sequence.

This is because the potentiometer adjusts the timing components in the astable multivibrator affecting the frequency of the clock signal.

Higher resistance or lower resistance can be set using the potentiometer.

Formulas:

Here are some formulas related to the components and parameters of the LED chaser circuit:

Frequency of the Astable Multivibrator IC 555:

The frequency of the square wave generated by the astable multivibrator is determined by the timing components resistor R and capacitor C and can be calculated using the formula:

f = 1.44 / (R_A + 2 * R_B) * C

where,

• f is the frequency in hertz Hz
• R_A​ is the resistance connected to pin 7.
• R_B​ is the resistance connected to pins 6 and 2
• C is the capacitance connected to pins 6 and 2.

LED Current Limiting Resistor:

The value of the current limiting resistor R_LED for each LED can be calculated using ohms Law:

R_LED = V_R / I_LED

where,

• V_R​ is the voltage across the resistor 12V to LED forward voltage
• I_LED​ is the desired LED current.

LED Forward Voltage Drop:

To calculate the voltage across the resistor, you need to determine the LED forward voltage drop V_LED​.

Duty Cycle of the Astable Multivibrator:

The duty cycle D of the astable multivibrator which represents the percentage of time the output is high can be calculated as:

D = R_B / R_A + 2 * R_B

How the Circuit is Build:

Building the LED chaser circuit involves connecting the components as described in the circuit description.

IC 555 Connections:

• Pin 1 connect to the ground supply.
• Pin 2 connected through a resistor to pin 6 and a capacitor to ground.
• Pin 3 connect to pin 14 of IC 4017F
• Pin 4 and 8 connect to VCC.
• Pin 5 connect to ground through capacitor 0.1uF.
• Pin 6 connect to one end of 10k resistor.
• Pin 7: connect to one leg of 100k pot.

IC 4017 Connections:

• Pin 8,13,15 connect to ground.
• Pin 16 is connect to the 12V DC supply
• Pin 3 to 11 connect each output to an LED with a current limiting 1k resistor and then to the ground.
• Connect the anode of each LED to the corresponding output pin of IC 4017 pin 3 to pin 11.
• Connect the cathode of each LED through a current limiting 1k resistor to the ground supply.

Notes:

• Use appropriate resistors to limit the current flowing through the LEDs.
• Double check the orientation of the ICs and LEDs to ensure they are connected correctly.
• Adjust the potentiometer to control the speed of the LED chasing effect.

Conclusion

This simple LED chaser circuit using IC 4017 can be implemented on a breadboard first for testing and later transferred to a more permanent solution like a PCB for a finished project.

Make sure to follow proper safety precautions when working with electrical circuits and if possible refer to datasheets for the specific ICs used in the circuit for additional details.

References

Chase (lighting)