This project creates a chase effect by causing a sequence of LEDs to light up one after another.
Learning about electronics in this way is enjoyable.
The special IC 555 chip generates a constant pulse.
This signal directs another chip IC 4017 to switch on and off its outputs in a specific manner.
The second chips outputs are all connected to the LEDs so they illuminate alternately.
The speed at which the LEDs chase one another can be changed by turning a knob.
It is powered by a 12V battery.
This project is suitable for beginners since it teaches you about two key electronic components and how they function.
It functions similarly like a mini course to sequence LED illumination.
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 Working:
Parts List:
| Type | Specification | Quantity |
|---|---|---|
| Resistors | 1k | 11 |
| 10k | 2 | |
| Potentiometer | 100k | 1 |
| Capacitors | PPC 0.01µF | 1 |
| Electrolytic 10µF 25V | 1 | |
| Semiconductors | IC 4017 | 1 |
| IC 555 | 1 | |
| LEDs 5mm 20mA | 11 |
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 pin 6, 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.
As a result the LEDs sequencing speed is modified.
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 4017 causing it to sequentially activate its outputs.
Each output of IC 4017 is connected to an LED and as the output changes 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 one 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 for LED chaser circuit:
Frequency of the Astable Multivibrator IC 555:
The frequency of the square wave generated by the astable multivibrator is measured by the timing components resistor R and capacitor C and is calculated using the formula:
f = 1.44 / (RA + 2 * RB) * C
where,
- f is the frequency in hertz Hz
- RA is the resistance connected to pin 7.
- RB 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 RLED for each LED is calculated using ohms law:
RLED = VR / ILED
where,
- VR is the voltage across the resistor 12V to LED forward voltage
- ILED is the desired LED current.
Duty Cycle of the Astable Multivibrator:
The duty cycle D of the astable multivibrator which represents the percentage of time the output is high is calculated as:
D = RB / RA + 2 * RB
How the Circuit is Build:
To build a Simple LED Chaser Circuit using IC 4017 follow the below steps for connections:
IC 555 Connections:
- Pin 1 connect to the ground supply.
- Pin 2 is 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 of positive supply of the circuit.
- Pin 5 connect to ground through capacitor 0.1uF.
- Pin 6 connect to one end of 10k resistor.
- Pin 7: connect to one terminal of 100k pot.
IC 4017 Connections:
- Pin 8,13,15 are 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 right resistors to limit the current flowing through the LEDs.
- Check twice the position 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 which uses an IC 4017 is first tested on a breadboard before being moved to a PCB for a more permanent option.
When working with electrical circuits take proper safety measures.
For more information check the datasheets for the particular integrated circuits and the circuit uses.