principle
The monostable circuit can be composed of discrete components and integrated logic gates, and can also be realized by a 555 timer or a single-chip dedicated monostable trigger.
definition
Monostable circuit means that the output signal of the circuit can only be stable in one state (logic high or logic low), but when the output of the circuit is in another state, it cannot be stable and will automatically return to the stable state.
Of course, bistable circuit means that the output signal of the circuit can exist stably in two states (0 or 1).
Extended data
design
The 555 timer was designed by Hans R. Camenzind for Signitic Company in 197 1 year. Signitic was later acquired by Philips.
555 chips produced by different manufacturers have different structures. The standard 555 chip integrates 25 transistors, 2 diodes and 15 resistors, and leads out through 8 pins (in DIP-8 package). The derivative models of 555 include 556 (integrating two 555 DIP- 14 chips) and 558 and 559.
The working temperature range of NE555 is 0-70 c, and that of military-grade SE555 is? Packages from 55 to+125 C.555 are divided into high-reliability metal packages (denoted by T) and low-cost epoxy packages (denoted by V).
Therefore, the complete labels of 555 are NE555V, NE555T, SE555V and SE555T. It is generally believed that the name of 555 chip comes from three 5kΩ resistors, but Hans Camenzind denied this statement and claimed that he chose these three numbers at random.
There are also low-power versions of 555, including 7555 and TLC555 with CMOS circuits. The power consumption of 7555 is lower than the standard 555, and its manufacturer claims that the control pin of 7555 does not need grounding capacitor like other 555 chips, and does not need decoupling capacitor to eliminate the noise between power supply and ground.
use
555 timer can work in three working modes:
Monostable mode: In this mode, the 555 function is a single trigger. Applications include timer, pulse loss detection, bounce switch, touch switch, frequency divider, capacitance measurement, pulse width modulation (PWM) and so on.
Unstable mode: In this mode, 555 acts as an oscillator. The 555 chip in this working mode is often used in circuits such as strong point, pulse generator, logic circuit clock, tone generator and pulse position modulation (PPM). If the thermistor is used as a timing resistor, 555 can constitute a temperature sensor, and the frequency of its output signal is determined by the temperature.
Bistable mode (or Schmidt trigger mode): When the DIS pin is empty and there is no external capacitor, the 555 works like an RS trigger and can be used to form a latch switch.
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