555 Timer IC – Working Principle, Block Diagram, Circuit Schematics

555 Timer IC

555 timer ic
timer ic 555


The 555 Timer IC becomes invented via “Signetic organization” and it becomes 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 multivibrator 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 Timer IC is used for wherein the temperature tiers from 0° to 70°C.

What’s a 555 Timer IC?

The IC 555 timer is 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 these IC tiers from 4.5V -15V DC supply. The functional parts of the 555 timer IC consist of a flip-flop, a voltage divider, and a comparator. 

The primary characteristic of this IC is to generate a correct timing pulse. In the monostable mode, the delay of this IC is managed by means of external components like a resistor and a capacitor. Within the astable mode, each obligation cycle & frequency is managed with the aid of two outside resistors and one capacitor.

555 Timer IC Pin Configurations

The 555 timer IC includes 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 that is used to deliver a 0 voltage to the IC.

Trigger Pin

Pin-2 is a trigger pin that 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 an 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 the threshold pin, then it contrasts with a reference voltage. The set kingdom of the FF may depend on 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 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 on the value of the two resistors and capacitors. Here the charging and discharging of the capacitors rely upon a particular voltage. 

The circuit diagram of the 555 timers in astable mode is shown below. If the voltage is applied to the beneath circuit, the capacitors constantly receive 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 the 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 the best-unmarried pulse while the timer gets an illustration from i/p of the cause button. The pulse period can depend 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 a fee and the timer circuit extends a high pulse, then it stays excessive until the capacitor absolutely discharges. If it is vital to beautify the time postpone, then a better fee of capacitor and resistor are required.

Monostable Mode

Bistable Mode Operation

In 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 an energetic pin, then the o/p of the IC circuit is going to an excessive level. If the low logic sign is given to the RST pin, then the o/p of the circuit goes to a 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 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?

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