LED chaser circuit using IC 4017 and 555

Here the circuit for a LED chaser or LED running light, which can be used as a decorative light, fancy light, chasing taillight for vehicles, etc.

The circuit consists of a 555 timer with 4017 sequential led flasher. The output of the 555 astable multivibrator is connected to the clock input of the decade counter. So that for each positive edge triggering of the clock input, the counter shifts the high state of the output in a sequence from output 0 to output 9. In a 4017 counter IC, only one output will be high at a time and the remaining outputs will be in the low state. And the shifting cycle repeats as like a ring counter. Thus the LEDs will visually see as like a light feeding in a rotary manner.led chaser circuit,555 timer with 4017 sequential led flasher

Here the Chaser circuit is designed with an ON time of 0.047s for each LED. The speed of the chaser can be varied by adjusting the time period of the clock input. That is the time period of the multivibrator. The time period of a 555 astable multivibrator can be calculated as T = .69 (R1+2R2) C.

By adjusting any of the resistor or capacitors values, the time period of the astable multivibrator and thereby chaser speed can be varied.

Components required

IC – IC1 – NE555, IC2 – 4017

Resistor – R1,R3 – 1K,R2 – 6.8k

Capacitor-C1 – 100uf,C2 – 4.7uf,C3 – 100nf

LED – D1-D10 – 5mm

Supply – 9V

LED knight rider circuit

Here the circuit of a 6 LED knight rider chaser. The circuit consists of a 4017 counter IC and a 555 astable multivibrator.  The square wave output from the 555 is connected to the clock input of the decade Counter IC 4017.  It provides the clock pulses for the counter.

The speed of chaser can be adjusted by varying the frequency of the astable multivibrator. Because the output is shifted with the rising edge of the input clock pulse.

Frequency of 555 astable multivibrator, f = 1.44/ (R1+2R2) C

Unlike from a normal chaser, in knight rider circuit the sequencing of the LED is arranged with diodes to obtain a to and fro motion of light. The output 0 to 6 lights the LED as to seem like the chaser moves forward and the remaining four to reverse direction. This cycle repeats again, which obtains a to and fro chasing effect.

components required

IC -IC1 – NE555, IC2 – 4017

Resistor – R1,R3 – 1K, R2 – 6.8k

Capacitor – C1 – 100uf, C2 – 4.7uf, C3 – 100nf

LED – D1-D6 – 5mm LED, D7-D16 – 1N4007

Supply – 9V

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2 Responses

  1. Dave V says:

    Question on LED chaser circuit. Getting a small project together for a scout group. Most of the 4017 & 555 circuits are pretty much the same with the variance of the resistor and capacitor values from ground to Vcc across pins 2,6,&7. Most of the circuits I’ve seen leave pin 5 open, but a few have shown a capacitor to ground.

    Two questions.

    1. The first circuit I bread boarded from another site did not have the capacitor, and after less than a minute it stopped chasing, but would continue for another short time with a power cycle. Any hints on what I did wrong?

    2. What does putting the capacitor to the pin 5 control get you?

    Be warned, I have some electronics knowledge from school MANY years ago, but just enough to be dangerous.

    • admin says:

      1. Can you share the circuit? It seems weird. I couldn’t find any reason for such a result. Normally the 4017 and 555 chaser circuits consist of a 555 astable multivibrator which provides square wave clock input to 4017 IC.

      2. The threshold and triggering voltages can be overridden by adjusting the voltage at Pin 5. That is the applied voltage at pin 5 is the threshold voltage and its half is triggering voltage. So if we don’t need to change the threshold voltage or trigger voltage values it can be left open. Then the threshold voltage will be 2/3Vcc and the trigger will be 1/3Vcc. While pin 5 is left open it has chances to affect by small fluctuations and noises so in order to avoid that a bypass capacitor is using at pin5.
      For reference: https://mechatrofice.com/circuits/555/555-timer-multivibrator-circuits

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