555 Timer is a reliable timer IC(Integrated Circuit) that can be used for number of circuit such as frequency divider, pulse width modulator, linear ramp generator, missing pulse detector, waveform generator, voltage controlled oscillator(VCO), FSK(Frequency Shift Keying) generator etc. Here we will illustrate another application of 555 timer which is LED flasher. Here we will illustrate LED flasher with one and two LED.
The following circuit diagram shows how we can make a single LED flasher with NE555 timer.
In the circuit drawing, the resistor R4 and C1 determines the LED flashing frequency. The frequency is determined by the time constant which is as follows.
\( \tau = R_3 C_2 = 100K\Omega \times 10 \mu F = 0.68s\)
So the frequency of blinking led is,
\( f = \frac{1}{0.68s} = 1.47Hz\)
The above NE555 timer one LED flasher can be modified to include another LED to make two LED flasher circuit. This is as shown below.
The frequency of the LED flashing is same as for the one LED flasher using 555 Timer.
So in this way we can create one or two LED flashing circuit with NE555 IC(Integrated Circuit). The above circuit works on the principle of NE555 astable multivibrator mode. Here we have used timer IC for led flashing. We can also use general purpose transistor like 2N3409 as illustrated in the tutorial Transistor based LED flasher Circuits.
The following video illustrates how the LED flasher works with 555 Timer.
