In this post we will learn how to assemble an IC 555 astable circuit for generating interesting LED flasher circuits with blinking and fading light effects with some minor modification and enhancements.
Why use an IC 555 Astable
The astable multivibrator mode is the most fundamental mode of operation of the IC 555. In this mode it basically functions like a free running oscillator. If this oscillator rate is reduced sufficiently, can be used for driving LED lights.
The wiring at the output can also be further modified for achieving interesting variations and light illumination patterns over the connected LED.
Some of the practical ways of this is explained here, circuits diagrams of LED flasher, ghost effect generator, alternate blinker, light fader etc are also included.
The article explains a few interesting and simple LED blinker circuit configurations using the ubiquitous IC 555.
The basic flashing mode has been kept intact yet various different attributions are provided to the circuit with its flashing rate and pattern.
The IC 555 is a complete package for the hobbyists. You can build numerous interesting circuits with this chip and make it to work as virtually any way you desire.
Though the circuit provides us with many application ranges, flashers configurations are more commonly associated with these chips.
These can be made to blink all types of lights at different rates depending upon individual preferences.
You can flash LEDs, torch bulbs, string lights or even mains AC lamps with circuits incorporating this IC.
Basically, to configure the IC as a flasher or blinker, it’s connected with its fundamental astable mutivibrator mode.
This configuration in fact requires just a couple of resistors and a couple capacitors to kick start the said functions.
Once the chip is assembled as an astable, we can go ahead and enhance the output in many different ways to get outstanding visual treats.
Let’s learn how a few fabulous IC 555 circuits with LED can be built with the following discussions, but first we would like to know what materials are needed for this.
Being a hobbyist you would want to have a bunch of assorted resistors in your box of goodies and also some selected values of capacitors. For the present projects you would require a handful of different value resistors and capacitors.
Parts List for the proposed flasher and fader circuit using IC 555
- Resistors rated at ¼ watt, 5 %, unless otherwise stated.
- Resistors – 1 K, 10 K, 680 Ohms, 4.7 K, 100 Ohms, 820 Ohms, 1 M etc.
- Capacitor – 0.01 uF, 470 uF, 220 uF, 1 uF
- Zener diode – 5.1 volts, 400 mW
- LED – Red, Green, Yellow 5mm
IC 555
IC 555 Pinouts
Video Demo
Creating Flashing and Fading LED Effects using IC 555 Circuit
The first figure shows the basic configuration associated with 555 ICs, here it is connected as an astable multivibrator. The resistors and the capacitor 1 uF can be experimented with to get different rates of blinking over the connected LED.
The LEDs can also be used with oter colors. The 1 K resistor can be replaced with lower values for increasing the intensity of the LED, however it should not be redced below 330 Ohms. Alternatively the 1 M resistor can be interchanged with a pot for attributing the circuit with variable blinking rate feature.
Making a Police Revolving Light Effect
The above circuit can be suitably modified for producing a revolving, flashing police light effect to the above constructed circuit.
Here by adding a network of a zener diode / resistor / capacitor, to the output of the circuit, just as shown in the figure, we can acquire a very peculiar effect with the generated illuminations of the LED.
The LED initially glows bright, then slowly dies down, but intermittently gives a high intensity pulse producing the discussed police warning roof light indicator illusion.
Random Light Effect Generator Circuit
The configuration shown in this figure enables us to use the circuit to generate random light patterns over the connected group of LEDs.
As shown, three LEDs are connected in conjunction with a couple of resistors and a capacitor. The two LEDs connected in parallel but with opposite polarity, flasg alternately at a particular rhythm while the third LED fluctuates at some other random rate.
The above effect can be simplified by the circuit shown below. Here, the LED which is connected to the 1 K resistor blinks at the fixed blinking rate, but the next LED which is connected to the ground switches rapidly at some other defined rate.
Adding a Spooky Effect to the LED
If you want to produce some strange illumination pattern over the LED discussed through the above circuits, them it can be simply done using just a couple of resistors at the output of the IC.
As can be seen in the figure, two resistors and a single resistor are connected at the output of the IC in a special way. The network switches ON the LED sharply, but switches it OFF slowly, producing quite a creepy visual effect.
Alternate Flasher Circuit
This configuration is pretty straightforward, as we all know; two LEDs can be connected to the IC output for generating an alternate blinking pattern over the connected LEDs.
The above circuit can be further modified as shown below by complely disarranging the network with the shown type. Here the LEDs though blink alternately, the intensity may fluctuate from dim to bright over the LEDs.
Light Fader Circuit Using IC 555
A very interesting light fading effect can be achieved by wiring up the IC 555 circuit as per the diagram shown below. The circuit switches ON the LED very gradually and does the same while switching it OFF, that is instead of shutting it off abruptly, does it very slowly.
555 Strobe Light Circuit
The next figure depicts a schematic design of the strobed-LED lighting system, which is based on a pair of commonly accessible integrated circuits (IC1, an LM7812 fixed 12 volt regulator, and IC2, a 555 oscillator/timer).
It is necessary to calculate the optimal duty cycle and frequency for the oscillator (IC2).
In other words, we're trying to perfect it when it comes to optimal frequency and duty cycle.
The circuit is set to run at a frequency of 3 Hz with a duty cycle of 50%. The operating frequency of this 555 strobe light circuit was determined with the help of a handy 1 uF capacitor C2 connected between pin6/2 and ground of the 555 timer/oscillator.
The 555 output (pin 3) is linked to the base of Q1, a TIP120 NPN Darlington transistor. The transistor, works like a switch and switches current to cause a strobing effect on the LED lighting module in response to the oscillator output (555 IC2).
555 Firefly Light Flash Simulator Circuit
It's not always the most elegant method to use a flashlight to attract fireflies for summertime evening entertainment with the kids.
This straightforward circuit comes in handy by more accurately simulating a firefly flash in terms of color, attack and decay times, brightness, and frequency.
Our firefly is customizable to mimic the flashing attributes of any of the 125 varieties of fireflies prevalent across the country, seems to last eternally, avoids damp soil, will not really eat bugs (but uses electrons provided by a 9-volt battery).
R1, R2, and C1 control the timing of a 555 timer, which produces a 0.25 Hz, high duty cycle square wave. A low duty-cycle signal is produced by inverting the output using the PNP transistor. The green LED's green luminous intensity slowly fades as the 220 uF capacitor discharges via the 680 ohm resistor (R4) and capacitor (C2).
An electric firefly that shines every four seconds is the final outcome. The green flash has distinct attack and decay characteristics and can last for around half a second.
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