555 timer is a mixed -scale integrated device combining simulation and digital functions.Generally made by bipolar type (TTL) process, which is called 555, and made of complementary metal oxides (CMOS) process is called 7555. In addition to a single timer, there is a corresponding dual timer 556/7556.555 timerThe range of power supply is wide and can work in 4.5V ~ 16V. 7555 can work at 3 ~ 18V. The output drive current is about 200mA. Therefore, its output can be compatible with the level of TTL, CMOS or analog circuits.
555 Application of timer
(1) Constract Schmidt trigger, the interface for the TTL system, plastic surgery circuit or pulse resolution, etc. (2) constitutes a multi -resonant to form a signal to generate circuit;
555 timer work principle
The function of the 555 timer is mainly determined by two comparators.The output voltage of the two comparators controls the status of the RS trigger and the discharge pipe.Add a voltage between the power supply and the ground. When the 5 foot is suspended, the voltage of the inverse input end of the voltage comparator A1 is 2VCC/3, and the voltage of the same phase input end of A2 is VCC/3.If the voltage of the input terminal TR is less than VCC/3, the output of the comparator A2 is 1, which can make the RS trigger 1 and make the output out of = 1.If the voltage of the threshold input terminal TH is greater than 2VCC/3, and the voltage of the TR end is greater than VCC/3, the output of A1 is 1, and the output of A2 can be set to 0 to make the output of 0.555 timer cost and reliable performance. You only need to connect a few resistors and capacitors to achieve and transform circuits such as multi -resonant oscillator, single -stable trigger and Schmidt trigger.It is also often used as a timer for instrumentation, household appliances, electronic measurement and automatic control.
555 timer pins chart
555 timer pins and pin description: There are eight feet in the 555 timer, and the voltage input end of each foot is different. UCC should be represented.The 1 foot is grounded, 2 feet are used as a triggering input port. The 3 foot is used as an output port. It can be controlled in the output state. After the 3 -pin output feels to the signal, the 6 and 2 feet will be made.Can be controlled.When the trigger of the 2 pin feels the input of A1, it will be placed in a state of reset.Of these eight feet, 2 feet and 6 feet are used as complementary feet. The 2 pin has a flat effect on the voltage and has no effect on elegance. At this time, the 3 -pin is in a high -voltage level state;The 6 foot is a threshold port, which has a effect on high -voltage flating, and does not play any effect at all in the low voltage level.The voltage of the 3 foot is very close to the voltage of the power supply, and its maximum output can reach 200mA.The 4 foot is the reset port. It must not be lower than the zero four volts. The output of the 3 foot in any state will make the output of the 3 foot in any state.The 5th foot is the control port of the entire timer. The 7 -pin is the discharge port of the timer and the 3 -pin is in a synchronous state, especially the levels they output are the same, but there are still differences between them.That is, the 7 -pin is a current without output. Therefore, the 3 pin is stipulated as a high (low), and the 7 -pin is stipulated as a virtual high (low).

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