Police Light Blinking using 555 Timer
In this project, it is shown how to design Police Lights using 555 Timer IC and CD4017 Counter IC. This circuit flashes Red LEDs for three times and then Blue LEDs for three times and this flashing action repeats continuously.
Introduction
In
this project, we will try to implement the blinking of police light. The
circuit uses 555 timer IC and a decade counter IC CD4017. Here, the 555 timer
runs in Astable mode. Decade counter 4017 counts
the incoming pulses and activates its outputs, and blinks the led accordingly.
555 Timer Based Police Lights Circuit Principle
Here 555 timer produces continuous pulses via pin
3(output pin). The width of these pulses can be varied by varying the
resistance (R1, R2) or capacitance (C1) connected in the circuit. These pulses
are given as input to the decade counter IC. For every incoming pulse the
output state of the decade counter gets incremented.
• For
1st pulse – blue led glow
• For
2nd pulse – (no connection) – all led’ s off
• For
3rd pulse – blue led glow
• For
4th pulse – (no connection)-all led’ s off
• For
5th pulse – blue led glow
• For
6th pulse – red led glow
• For
7th pulse – all led’ s off
• For
8th pulse – red led’ s glow
• For
9th pulse – all led’ s off
• For
10th pulse –red led’ s glow
• For
11th pulse – blue led’ s glow.
This process repeats continuously.
Circuit Components
·
555 Timer IC - 1
· 4017 IC - 1
· Resistor
10K - 2, 1K - 2, 220ohm - 8, 470ohm - 5
· Capacitor
10uF - 1
· Transistor 2N2222 - 2
· Led (red
and blue) - 2 pieces each
· Single stand Wire 2m - 1
· 12V 1A Adapter - 1
· Breadboard
CIRCUIT DIAGRAM
CONNECTIONS
- · 555 Timer IC connected to the breadboard.
- · Pin 1 of 555 Timer IC is GND and Pin 4 & 8 connected to the positive supply of the adapter.
- · Pin 2 & 6 of 555 Timer IC is connected with each other.
- · 1k Resistor 1st leg is connected to the positive supply and Resistor 2nd leg connected to the Pin 7 of 555 Timer IC.
- · 10K Resistor 1st leg is connected to the Pin 6 of 555 Timer IC and Resistor 2nd leg connected to the Pin 7 of 555 Timer IC.
- · 10uF Capacitor positive leg connected to the Pin 2 of 555 Timer IC and Capacitor negative leg is GND.
- · Pin 3 of 555 Timer IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the pin 14 of 4017 IC.
- · Pin 16 of 4017 IC connected to the positive supply and Pin 8, 12, 13 & 15 of 4017 IC are GND.
- · Pin 3 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(1st) 2N2222 2nd leg(B).
- · Pin 4 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(1st) 2N2222 2nd leg(B).
- · Pin 10 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(1st) 2N2222 2nd leg(B).
- · Transistor(1st) 2N2222 1st leg is GND and Transistor(1st) 3rd leg connected to Led negative leg and led positive leg connected to 470 ohm Resistor and Resistor 2nd leg connected to the positive supply.
- · Pin 1 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(2nd) 2N2222 2nd leg(B).
- · Pin 6 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(2nd) 2N2222 2nd leg(B).
- · Pin 11 of 4017 IC to connected 220 ohm Resistor and Resistor 2nd leg connected to the Transistor(2nd) 2N2222 2nd leg(B).
- ·
Transistor(2ND) 2N2222 1st leg is GND and 3rd leg to connected led
negative leg and led positive leg connected to the 470 ohm resistor and
resistor 2nd led connected to the positive supply.
·
555
Timer
Here, 555 timer runs in free running mode i.e.
Astable Mode. It produces pulses whose width can be varied. 2nd and 6th pin
numbers are shorted to allow triggering after every cycle. 4th pin is connected
to Vcc.
4017 Decade Counter
It is a 10 bit counter with ten decoded output pins.
It counts the incoming pulse inputs. The supply voltage range is -0.5 to +22V.
The high pulse on the reset pin clears the count to zero. The output states
(Q0,Q2,Q4) are configured to flash the blue LED’s 3 times and the states Q5, Q7
and Q9 are configured 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.
Limitations of Police Lights Circuit
•
The values of the resistors R1, R2 and capacitor
C1 should be same to get perfect flash lightning.
•
We can change the value of resistors and
capacitors to get variable lightning also.
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