Ic 555 is an integrated circuit (chip) implementing a variety of timer and multivibrator applications. The IC was designed by Hans R. Camenzind in 1970 and brought to market in 1971 by Signetics (later acquired by Philips). The original name was the SE555 (metal can)/NE555 (plastic DIP) and the part was described as "The IC Time Machine". It has been claimed that the 555 gets its name from the three 5-kohm resistors used in typical early implementations, but Hanz Camenzind has stated that the number was arbitrary The part is still in wide use, thanks to its ease of use, low price and good stability. As of 2003 it is estimated that 1 billion units are manufactured every year.
Depending on the manufacturer, the standard 555 package includes over 20 transistors, 2 diodes and 15 resistors on a silicon chip installed in an 8-pin mini dual-in-line package (DIP-8).
The 556 is a 14-pin DIP that combines two 555s on a single chip. The 558 is a 16-pin DIP that combines four slightly modified 555s on a single chip (DIS & THR are connected internally, TR is falling edge sensitive instead of level sensitive).
Also available are ultra-low power versions of the 555 such as the 7555 and TLC555. The 7555 requires slightly different wiring using fewer external components and less power.
The connection of ic 555 as follows:
- GND(1)Ground, low level (0V)
- TRIG(2)A short pulse high-to-low on the trigger starts the timer
- OUT(3)During a timing interval, the output stays at +VCC
- RESET(4)A timing interval can be interrupted by applying a reset pulse to low (0V)
- CTRL (5)Control voltage allows access to the internal voltage divider (2/3 VCC)
- THR (6)The threshold at which the interval ends (it ends if U.thr → 2/3 VCC)
- DIS (7)Connected to a capacitor whose discharge time will influence the timing interval
- V+, VCC(8) The positive supply voltage which must be between 3 and 15 V