555 TIMER AJAR FLASHER/ALARM
K.R.ANUPRIYA, T.ANJOLIE & M.JANANI
Introduction to 555 Timer:
‘’A semi-conductor device that controls various modes of on/off states in electrical systems or circuits. The 555 timer is one of the most widely used types of integrated circuits.”
The 555 timer IC was first introduced around 1971 by the Signetics Corporation as the SE555/NE555 and was called "The IC Time Machine" and was also the very first and only commercial timer IC available. It provided circuit designers with alternatively cheap, stable, and user-friendly integrated circuit for both monostable and astable applications. Since this device was first made commercially available, a myriad of novel and unique circuits have been developed and presented in several trade, professional, and hobby publications. The past ten years some manufacturers stopped making these timers because of competition or other reasons. Yet other companies, like NTE (a sub division of Philips) picked up where some left off. Although these days the CMOS version of this IC, like the Motorola MC1455, is mostly used, the regular type is still available; however there have been many improvements and variations in the circuitry. But all types are pin-for-pin plug compatible. In this tutorial the 555 timer is examined in detail along with its uses, either by itself or in combination with other solid state devices. This timer uses a maze of transistors, diodes and resistors and for this complex reason a more simplified (but accurate) block diagram is used to explain the internal organizations of the 555.The 555 is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed and invented by Hans R.Camenzind. It was designed in 1970 and introduced in 1971 by Signetics (later acquired by Philips). The original name was the SE555/NE555 and was called "The IC Time Machine". The 555 gets its name from the three 5-kOhm resistors...