555 timer

555 timer;- What is the 555 timer?

- Pin configurations of the 555 timer ;

- 555 timer in astable operation ;

- 555 timer in monostable operation ;

- What are the 555 timer applications?

555 Timer;555 Timer;The 555 timer is one of the most remarkable The 555 timer is one of the most remarkable integrated circuits ever developed. It comes in integrated circuits ever developed. It comes in a single or dual package and even low power a single or dual package and even low power cmos versions exist - ICM7555. cmos versions exist - ICM7555.

Common part numbers are;Common part numbers are;

LM555, NE555, LM556, NE556. LM555, NE555, LM556, NE556.

Pin configurations

The 555 timer consists of;The 555 timer consists of;

two voltage comparatorstwo voltage comparatorsa bi-stable flip flopa bi-stable flip flop

a discharge transistora discharge transistorand a resistor divider network.and a resistor divider network.

555 timer in astable operation ;

555 timer in monostable operation ;

Applications using 555 timer;

-Random Flashers; -A light dimmer;

; -A car tachometer -Traffic Lights;

-Infra Red (IR) remote control;

'Random' Flasher for 8 LEDs Project

What is a light dimmer?

A light dimmer is a means of controlling the "brightness" level of a lamp

For the light dimmer to work the 555 timer is configured as a "variable cycle", astable oscillator running some where around 300

Hz.

What is a car tachometer?What is a car tachometer?

A tachometer is simply a means of A tachometer is simply a means of counting the engine revolutions of an counting the engine revolutions of an

automobile engine.automobile engine.

In this suggested idea a NE555 timer is In this suggested idea a NE555 timer is configured as configured as a monostablea monostable or one shot. or one shot.

The period of the 555 timer for our car The period of the 555 timer for our car tachometer is determined by the resistor from tachometer is determined by the resistor from the 9V regulated supply to pin 7 (50K) and the the 9V regulated supply to pin 7 (50K) and the capacitor from pin 6 and ground (0.1 uF). Time capacitor from pin 6 and ground (0.1 uF). Time "T" = 1.1 RC  or  1.1 X 50,000 X 0.1 X10 -6  =  "T" = 1.1 RC  or  1.1 X 50,000 X 0.1 X10 -6  =  0.0055 or 5.5 mS (milli-seconds).0.0055 or 5.5 mS (milli-seconds).

Extra:Extra:

Supply is taken from the 12V automobile Supply is taken from the 12V automobile system and for the NE555 timer car system and for the NE555 timer car tachometer is reduced to a regulated 9V by the tachometer is reduced to a regulated 9V by the 15 ohm resistor in conjunction with the 9V 15 ohm resistor in conjunction with the 9V zener diode. Note that the 10 uF polarised zener diode. Note that the 10 uF polarised capacitor must be placed physically as close capacitor must be placed physically as close as possible to the supply pin 8. It is depicted in as possible to the supply pin 8. It is depicted in the schematic diagram in this manner purely the schematic diagram in this manner purely for clarity.for clarity.

Traffic Light

The time taken for the complete red - red & amber - green – amber sequence can be varied from about 7s to about 2½minutes by adjusting the 1M preset.

IR Remote Control

We know that if we want to calculate charging, discharging time and the frequency, we will use these equs.

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Questions

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