555 Timer IC
In the year 1971 by Hans R. Camenzind has designed the 555 timer integrated circuit with the contract of Signetics. Later on it came to Dutch company which is Philips semiconductors. The manufacturing of 555 timer IC includes the transistors, diodes, and resistors on the silicon chip which are on the 8 – pin mini dual in line packages. There are different types of timers available like 556 which include the 14 pin dual in line package are gathering the 555s on one chip. The other types of timers are 558 and 559 for both timers. It contains 16 pin dual in line package. The temperature range of the NE555 timer is from 0 °C to +70 °C.
The SE555 part number is designed for the military purpose with a temperature range from -55 °C to +125 °C. This was accessible for both high reliability metal with low price of epoxy plastic packages. The 555 timer got the name from the three 5 k ohm resistors, but the number was assumed as an arbitrary and it is a hypothesized. In the 555 timer there is a low power version like 7555 and the COMS TLC555.
What is a 555 timer IC?
555timer is an integrated circuit which contains 8 pins and the description of each pin is given in the pin description. This timer is used in the pulse generation, oscillators and in different timer circuits. The 555timer produces time delays in the oscillator, also in flip flop elements and the 555 timer contains three modes which are Astable, Bistable and Monostable modes. The following diagram shows the 555 timer integrated circuit.
555 Timer IC
Pin Description of the 555 Timer IC
The 555 timer consists of 8 pins and these pins contain different types of functions. The following table shows the functions of a 555 timer IC and its pin diagram
Pin Description of 555 Timer
| Pin No | Pin Name | Function of the Pin |
| 1 | Ground | This pin is connected to Ground |
| 2 | Trigger | This pin appears like a starter pistol to start the IC. This trigger is an active low trigger. Because when the 555 timer starts if the voltage on pin 2 is below 1/3 of the main voltage. The output of the pin 3 goes higher when the 555 timer is triggered through pin 2 |
| 3 | Output | The pin 3 is an output pin and the output is digital nature. The output may be low or high. If the output is low,then the value is close to 0V. If the output is high, then the value is close to +5V. The output pin is connected to load to power the 555 timer |
| 4 | Reset | This pin is used to restart the 555 timer and it is connected to the supply voltage. |
| 5 | Control Voltage | This is used to control the voltage and it is connected to the ground in most of the 555 circuits through a small capacitor of 0.1 µF. This capacitor is used to avoid the faction in the power supply voltage. |
| 6 | Threshold | This pin is used to maintain the voltage across the capacitor which is discharged with the help of the pin 7. |
| 7 | Discharge | This pin is a discharge pin it discharges the external capacitor and worked as a conjunction with the resistor to control the time interval. |
| 8 | Power supply | The 555 timer gets the power supply from this pin the maximum power supply is not more than +5v. |
Block Diagram of 555 Timer IC
The following block diagram shows the 555 timer integrated circuit. It consist of two comparators that means it has two op-amps, R-S flip flop, resistive network and also with two transistors. The resistive network contains three equal resistors which will act as a voltage driver. The first comparator compares the threshold voltage by combining the reference voltage and 2/3vcc volts. The trigger voltage is compared with the second comparator by comparing the reference voltage and 1/3Vcc volts.
Block Diagram of 555 Timer IC
The output of two comparators is given to the flip flop and the state of the flip flop is assumed according to the two comparator output. . The path of the capacitors connected externally is provided by the saturated transistor. The other transistor is connected to the reset pin. If any pulse is applied to the reset pin, then the terminal resets the whole timer without bothering of any input.
Working Principle of 555 Timer
The working principle of the 555 timer is by considering the block diagram of the 555 timer IC. The first comparator has threshold input to pin 6 and control inputs for pin 5. The control input is used in some of the applications, but most of the applications the control input is not used hence the control voltage is equal to +2/3 Vcc. The output of the first comparator is given to the flip flop of set pin input. Whenever the threshold voltage overcomes the control voltage then the first comparator is set to flip flop and the output is very high.
The high output gives the flip flop saturation which discharges the transistor and capacitor these are connected to pin 7. To the pin 3 the complementary signal is connected and the output of this pin is low. These conditions are applied unless the comparator 2 triggers the flip flop. If any cases occur threshold input is less than the 2/3 Vcc, then the first comparator can’t charge the charge flip flop. Hence, the first comparator has the chances of high flip flops output high.
If the voltage at the trigger input is less than the 1/3 Vcc then the output of the flip-flop changes to minimum or low. If the second comparator triggers output is minimized to the flip flops. This situation is kept on continuing to the voltage of the trigger input. The output is low for the second comparator with the help of flip flops.
Functions of 555 timer IC
- The 555 timer power supply has high range from +5volts to +18 volts.
- The load current for the 555 timer is sourcing 200 mA.
- The 555 timer has high output current and the output is driven for the TTL.
- To change in temperature in the 555 timer it has a temperature stability of 50 ppm/ degree.
- The duty cycle of the 555 timer has the maximum power dissipation.
Applications of 555 Timer Integrated Circuit
In the electronic circuit there are different types of 555 timers are used. Anyhow, in most of the cases the basic circuit has the astable or the small circuit. The applications used in the operating frequency, duty cycle, and in the pulse time duration. To the 555 timer the external components are connected to interface the device.
Advantages of 555 Timers
- The 555 timer is used in various types like oscillators, delays, pulse generation.
- In the 555 timer the increment of time is adjustable from microsecond to hours.
This article is about the basics of 555 timers IC and its working principle. I hope by reading this article you have gained some basic knowledge about the 555 timers. If you have any queries regarding this article or to implement any electrical projects. Please comment in the below section. Here question for you, what is mean by ground load?
Photo Credits:
- Pin Configuration of 555 Timer learningaboutelectronics
- Block Diagram of 555 Timer IC circuitstoday