555 Timer IC

The IC 555 timer become invented via “Signetic organisation” and it become termed as SE or NE555 timer. Generally, it’s miles a monolithic timing circuit that offers unique and surprisingly stable delays of time or oscillation. These styles of ICs are very cheap and dependable in value whilst we in comparison with the OP-Amp programs in the same areas. Those ICs are used as an astable and monostable multivibrators in virtual logic probes, DC-DC converters, tachometers, analog frequency meters, voltage regulators, temperature controlled and measurement devices. The IC SE555 is used for wherein the temperature tiers from – 55°C to 125°C and the IC NE555 is used for wherein the temperature tiers from 0° to 70°C.

What’s a 555 Timer IC?

The IC 555 timer is a one type of chip used in distinctive programs like an oscillator, pulse era, timer. The designing of IC 555 timers can be achieved by way of using diverse electric and electronic components like transistors, resistors, diodes and a turn flop. The running variety of this IC tiers from 4.5V -15V DC supply. The functional parts of the 555 timer IC consist of flip-flop, voltage divider and a comparator. The primary characteristic of this IC is to generate an correct timing pulse. In the monostable mode, the delay of this IC is managed by means of the external components like a resistor and capacitor. Within the astable mode, each the obligation cycle & frequency are managed with the aid of two outside resistors and one capacitor.

555 Timer IC Pin Configurations

The 555 timer IC include 8-pins where each pin has some function. The pin configuration of this IC is shown underneath.

555 Timer IC Pin Configurations


Pin-1 is a GND pin which is used to deliver a 0 voltage to the IC.

Trigger Pin

Pin-2 is a trigger pin which is used to transform the FF from set to RST (reset). The output of the timer depends on the amplitude of the outside cause pulse this is carried out to the trigger pin.

Output Pin

Pin-three is an output pin.

Reset Pin

Pin-four is a RST pin. While the bad pulse is implemented to this pin to disable or reset, and fake triggering may be neglected by connecting to VCC.

Control Voltage Pin

Pin-five is the manipulate voltage pin used to govern the pulse width of the output waveform and also the tiers of threshold and trigger. While an outside voltage is implemented to this pin, then the output waveform may be modulated

Threshold Pin

Pin-6 is the brink pin, whilst the voltage is carried out to threshold pin, then it contrasts with a reference voltage. The set kingdom of the FF may be depends at the amplitude of this pin.

Discharge Pin

Pin-7 is the discharge pin, when the output of the open collector discharges a capacitor between the periods, then it toggles the output from excessive to low.

Supply Terminal

Pin-eight is the voltage supply pin that’s used to deliver the voltage to the IC with admire to the ground terminal.

Working Modes of 555 Timer IC

The working modes of a 555 timer are astable, bistable and monostable. Each mode of operation indicates with a circuit diagram and its output.

Astable Mode Operation

In this mode, the circuit of the IC 555 timer produces the continuous pulses with exact frequency primarily based at the value of the two resistors and capacitors. Here the charging and discharging of the capacitors relies upon on a particular voltage. The circuit diagram of the 555 timer in astable mode is shown under. If the voltage is applied to the beneath circuit, the capacitors constantly receives charged through two resistors and generates pulses continuously. Within the following circuit pins 2 & 6 are shorted collectively for countless re-set off the circuit. If the o/p trigger pulse is high, then capacitor within the circuit completely discharges. Long time delays are executed by way of using the higher values of the resistors and capacitors.

Astable Mode

Monostable Mode Operation

In this mode, the circuit generates best unmarried pulse while the timer gets an illustration from i/p of the cause button. Pulse period can be depends on the values of the resistor and capacitor If an activating pulse is applied to the i/p of the circuit via a push button, then the capacitor gets fee and the timer circuit extends a high pulse, then it stays excessive until capacitor absolutely discharges. If it is vital to beautify the time postpone, then better fee of capacitor and resistor are required.

Monostable Mode

Bistable Mode Operation

On this mode, the circuit produces 2-stable nation alerts that are low and states. The o/p indicators of low and high kingdom signals are managed by means of reset & activate the i/p pins, now not by using the charging & discharging of capacitors. If a low good judgment sign is given to energetic pin, then the o/p of the IC circuit is going to excessive level. If the low logic sign is given to the RST pin, then the o/p of the circuit goes to low stage.

Bistable Mod

Accordingly, that is all about 555 timer IC basics, pin description and operating modes. We hope which you have were given a higher know-how of this idea . Furthermore¸any queries regarding this idea or engineering task thoughts, please provide your valuable guidelines by using commenting within the remark segment below. Here’s a question for you, what’s the main feature of a 555 timer IC?