@▷ Two LED Flasher by 555 Timer | Diagram for Schematic

Two LED Flasher by 555 Timer

Circuit Project Description

The purpose of building this circuit is to create a LED flasher with alternating sequence from the two LEDs where the operation is based on the functionalities of a 555 timer integrated circuit.

Terminology555 – a highly stable device for generating oscillation or accurate time delays used in pulse width/position modulation, sequential timing, time delay generation, linear ramp generator, precision timing, and pulse generation due to its features such as normally open and normally off output, temperature stability, output and supply TTL compatible, adjustable duty cycle, and operates in both astable and monostable mode4N25 – a general purpose optocoupler that consists of a gallium arsenide infrared emitting diode driving a silicon phototransistor in a 6-pin dual in-line package used in microprocessor inputs, digital logic inputs, and power supply regulators due to its features such as high isolation voltage between input and output, operating temperature up to +110ºC, and available in wide-lead spacingCircuit Explanation

The main component of the circuit is focused on the 555 timer integrated circuit which is also being used in other circuit requiring multivibration and timing. It can be configure to three operating modes namely:

-Monostable – produces a single (one shot) pulse upon receiving a trigger signal

-Astable – produces a continuous square wave or rectangular pulses as with an oscillator

-Bistable – produces a state of set and reset as with a flip-flop or Schmitt trigger

When operating in bistable mode, it may be utilized in bounce free latched switches, pulse-type waveform processing, and railroad track designing. When operating in astable mode, it may be utilized in pulse position modulation, security alarms, tone generation, logic clocks, pulse generation, lamp flashers, and light emitting diode. When it operates at monostable mode, it may be utilized in pulse width modulation (PWM), capacitance measurement, frequency divider, touch switches, bounce free switches, missing pulse detection, and timers.

The alternating flashes produced from the two LEDs D1 and D2 can be of different colors if desired, for added physical feature and attraction. The use of 250K ohm trimmer R3, together with the changing of the values of capacitor C1, is for the adjustment of the frequency of oscillation or alternation of the sequence of lighting.

The circuit can be supplied by a battery source or a separate power supply and because of the addition of optocouplers IC2 and IC3, an external circuit can be driven at the same time with LEDs D1 and D2 for different types of applications like the indication of an alarm. The use of optocoupler is to all the input signal to the LED to be converted into varying light which is detected by the photodiode and uses light emitting diode to transmit light via an optically transparent barrier between two isolated circuits.

Part List
R1-2= 1.5Kohm
R3= 250Kohm trimmer
R4-5= 470 ohm
C1= 10uF 16V
C2= 100nF 63V
C3= 100uF 16V
IC1= 555
IC2-3= 4N25 optocoupler
D1-2= LED  3mm
BATT= 9V Battery
S1= Push Button or switch on-off

The flasher circuits using LEDs can be seen widely in motorcycles and cars for their tail, brake, turn light applications. These LEDs can also come in different monochromatic colors such as white, red, and amber. One of the most important use of the flasher circuit is providing a visual indication of a hazardous situation from its warning lights.

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