Police Lights using 555 Timer IC
This circuit simulates the police car lights by alternate flashing. This circuit flashes red LED s for three times and blue LED’s for three times. This flashing action performs continuously.
This circuit uses 555 timer and a decade counter. Here, 555 timer runs in astable mode. Decade counter 4017 counts the incoming pulses that is for first pulse Q0 becomes high and for second pulse Q1 becomes high and so on again for 10th pulse Q0 state becomes high.
Circuit Diagram of Police Lights using 555 IC:-
Electronic Ingredients for Circuit :-
- NE555 timer
- 4017 decade counter
- 1n4148 diodes – 6
- 1k Resistor(1/4 watt) – 1
- 22k Resistor(1/4 watt) – 1
- 470 ohm Resistor(1/4 watt) – 8
- 2.2uF Electrolytic capacitor(16V or 25V) – 1
- Blue LED’s – 2
- Red LED’s – 2
- 9v battery – 1
- Connecting wires
555 IC :- Here 555 timer runs in free running mode. It produces pulses whose width can be varied. 2nd and 6th pins are shorted to allow triggering after every cycle. 4th pin is connected to Vcc to avoid sudden resets.
4017 IC :- It is a 10 bit counter with ten decoded outputs. It counts the incoming pulses. The supply voltage range is -0.5 to +22V. The high pulse on the reset pin clears the count to zero. The speed of operation of this IC is up to 10 Mhz. The ouput states (Q0,Q2,Q4) are ORed to flash the blue LED’s 3 times and the states Q5, Q7 and Q9 are ORed to flash the red LED’s 3 times. Based on the outputs of 4017 IC, two transistors (NPN) switches the LED’s ON and OFF. Resistors R3, R4, R5, R6 are used to protect the LED’s from high voltage.
