The 555 Timer IC Working and PIN Diagram

The 555 timer IC: working and pin diagram

The 555 timer IC is a most common used ic in electronics projects. It is a simple integrated circuit involving a single 8-bit micro-controller and some peripherals or a complex one involving system on chips. 555 timer ic provides time delays as an oscillator and as a flip-flop element in other projects.

Timer ic 555 was introduced in 1971 by an American company Signets. It is being used in mostly projects of electronics due to its low price, easy to use and stability. Most of the electronics companies making  Timmer IC 555. It is mostly used in led flasher circuit using 555 for fun of learners.

The standard 555 timer IC includes 25 transistors, 2 diodes and 15 resistors on a silicon chip. The 555 ic consists of 8-pin mini dual-in-line package (DIP-8). We try to understand the pins diagram with functions.

Circuit Diagram of Timer ic 555

Pin diagram and description

Pin 1 (Ground):
Connects to the 0v power supply it is also called ground pin.

Pin 2 (Trigger):
It make output HIGH as detects 1/3 rail voltages. Pin 2 trigger has control over pin 6 threshold. When pin 2 is LOW and pin 6 is also LOW then output goes and stays HIGH. When pin 6 HIGH and pin 2 goes LOW then output goes LOW while pin 2 LOW. This pin has a very high impedance about 10M and will trigger with (about 1uA).

Pin 3 (Output):
Output of the timer is available at this pin. There are two style output (positive and negative) so the out can be connected with two ways. One way is to connect output pin (pin 3) and ground pin (pin 1) or between pin 3 and pin (pin 8).

Pin 4 (Reset):
Pin 4(Reset) is used to reset or disabled, negative pulse is applied to pin 4 for resetting. You must be taken below 0.8v to reset the chip.

Pin 5 (Control):
Threshold and trigger levels are controlled using this pin 5. The pulse width of the output is controlled by using this pin.

Pin 6 (Threshold):
This pin detects 2/3 of rail voltage to make output LOW only if pin 2 is HIGH. Pin 6 has a very high impedance about 10 M and will trigger.

Pin 7 (Discharge):
Open collector output which may discharge a capacitor between intervals. In phase with output is controlled with this pin 7

Pin 8 (Supply):
PIN 8 is also called supply pin. Positive supply between 3 to 16 volts can be applied by using this pin.

Applications of 555 Timer circuits

To understand the full working of 555 ic visit the following Projects base on this ic.

Videos of Projects with timer IC 555


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