IC NE 555 Timer- introduction

IC NE 555 Timer

555 timer IC is the cheap, popular and precise timing device used in various applications. It gets the name from the three 5KΩ resistors that are used to generate two comparator reference voltages. This IC is operated as monostable, bistable or astable multivibrater to produce a variety of applications.

This IC comes with bipolar 8 pins dual in-line package. It consists of 25 transistors, 2 diodes and 16 resistors arranged to form two comparators, flip-flops, and high current output stage.

Pin Description

The following is the Pin Description

Pin 1-Ground: It is connected to ground as usual. For the timer to function this pin should be connected to ground.

Pin 2-TRIGGER: The negative input comparator No 1. A negative pulse on this pin “sets” the internal Flip-flop when the voltage drops below 1/3Vcc causing the output to switch from a “LOW” to a “HIGH” state

Pin 3-OUTPUT: This pin also has no special function. This pin is drawn from PUSH-PULL configuration formed by transistors.This pin gives the output.

Pin 4-Reset: There is a flip-flop in the 555 IC timer chip. The output of flip-flop controls the chip output at pin 3 directly. This pin is connected to Vcc for the flip-flop to stop from hard resetting.

Pin 5-Control Pin: The control pin is connected from the negative input pin of comparator one. The function of this pin to give the user the direct control over the first comparator.

Pin 6-THRESHOLD: Threshold pin voltage determines when to reset the flip-flop in the timer. The threshold pin is drawn from positive input of comparator1.

Pin 7-DISCHARGE: The discharge pin is connected directly to the Collector of an internal NPN transistor which is used to “discharge” the timing capacitor to ground when the output at pin 3 switches “LOW”.

Pin 8-Power or VCC: This pin also has no special function. It is connected to a positive voltage.

Working Modes OF 555 Timer IC

The 555 timer IC operates in modes

Astable mode

Monostable mode

Bistable mode

Astable mode

Astable mode means there will be no stable levels at the output. Thus the output will fluctuate from high and low. This character of the astable output is used as a clock or square wave output for many applications.

Features of 555 timer IC

It operates from a wide range of power supplies ranging from + 5 Volts to + 18 Volts supply voltage.

Sinking or sourcing 200 mA of load current.

The external components should be selected properly so that the timing intervals can be done in several minutes along with the frequencies exceeding several hundred kiloHertz.

The output of a 555 timer can drive a transistor-transistor logic (TTL) due to its high current output.

It has a temperature stability of 50 parts per million (ppm) per degree Celsius change in temperature, or equivalently 0.005 %/ °C.

The duty cycle of the timer is adjustable.

The maximum power dissipation per package is 600 mW and its trigger and reset inputs has logic compatibility.

Thus, this is all about making of Blinking LED using a 555 timer IC. We hope that you have got a better understanding of this concept. Furthermore, any queries regarding this topic or 555 timer based projects, please give your valuable suggestions by commenting on the comment section below.

Manmohan Pal

Mob. 8989811397 

mannmohanpal@gmail.com