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.
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.
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.
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