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555 timer_图文

?Description ?Features ?Pins ?Principle ?Application ?Summary

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The 555 monolithic timing circuit is a highly stable controller capable of producing accurate time delays , or oscillation . In the time delay mode of operation , the time is precisely controlled by one external resistor and capacitor . For a stable operation as an oscillator , the free running frequency and the duty cycle are both accurately controlled with two external resistors and one capacitor . The circuit may be triggered and reset on falling waveforms , and the output structure can source or sink up to 200mA .

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Turn-off time less than 2uS. Max operating frequency greater than 500kHz. Timing from microseconds to hours. Operates in both astable and monostable modes. High output current. Adjustable duty cycle. TTL compatible. Temperature stability of 0.005%per ℃

The picture above is 555 timer pins, each pin has a different function .

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The 555 timer consists of four parts, Resistor voltage divider ,comparator ,S-R flip-flop ,and inverter.
comparator Resistor voltage divider Flip-flop inverter

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The 555 has three main operating modes , Monostable , Astable , and Bistable. Each mode represents a different type of circuit that has a particular output .

V CC R
in
7 6 2 4 8

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555
1

out
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2 VCC 3

t

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uo

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C

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circuit

Wave from

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7 4 8

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2 VCC 3
1 VCC 3

RB

555 3

uo

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uo

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C

C5

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t

VCC2

VCC1
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uo2

R
7

4 8

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3

uo1
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2VCC/3 1VCC/3 t

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circuit diagram
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Precision timing ? 2. Pulse generation ? 3. Sequential timing ? 4. Time delay generation ? 5. Pulse width modulation

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The 555 timer is a simple integrated circuit that can be used to make many different electronic circuits. The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation , and oscillator applications.