CN105207654A

CN105207654A - Timing circuit based on 555 integrated chips

Info

Publication number: CN105207654A
Application number: CN201510708999.XA
Authority: CN
Inventors: 张钰玲
Original assignee: Guangxi Vocational and Technical College
Current assignee: Guangxi Vocational and Technical College
Priority date: 2015-10-28
Filing date: 2015-10-28
Publication date: 2015-12-30

Abstract

The invention provides a timing circuit based on 555 integrated chips. The timing circuit adopts the 555 integrated chips to form a preceding-stage pulse wave generating circuit and a post-stage timing circuit; an RC resistor-capacitor unit of the post-stage timing circuit is charged by the pulse wave outputted by the preceding-stage pulse wave generating circuit; therefore, the timing time of the timing circuit depends on the RC time constant and the duty ratio of the pulse wave; as the duty ratio of the preceding-stage pulse wave generating circuit is adjustable, the timing time is longer if the duty ratio of the pulse wave is smaller. The timing time can be lengthened by reducing the duty ratio of the pulse wave under the condition that the RC time constant is the same; therefore, compared with the timing circuit composed of the traditional 555 integrated chips, the timing circuit based on 555 integrated chips, disclosed by the invention, is longer in timing time and can meet the demand of more control occasions.

Description

A kind of timing circuit based on 555 integrated chips

Technical field

The present invention relates to a kind of timing circuit, specifically a kind of timing circuit based on 555 integrated chips, belongs to electronic technology field.

Background technology

In all kinds of automatic control system, conventional 555 integrated chip composition timing circuits.The timing circuit of tradition 555 integrated chip composition, timing is directly proportional to the time constant of charge circuit Resistor-Capacitor Unit, in order to obtain longer timing, need increase resistance and the capacitance of charge circuit.But resistance can only increase to M Ω magnitude, because of the resistance that market provides, resistance maximum namely M Ω magnitude, meanwhile, its thermal noise of large valued resistor is also larger; And capacitance can only increase to 100 μ F magnitudes, because capacitance increases, its volume also increases, and electric leakage also increases thereupon.Therefore, the timing circuit of traditional 555 integrated chip compositions, its timing is general all shorter.But control occasion at some, need longer timing, the timing circuit of traditional 555 integrated chip compositions just can not meet the demands.

Summary of the invention

The object of this invention is to provide a kind of timing circuit based on 555 integrated chips, with the problem that the timing solving traditional 555 integrated chip timing circuits is shorter.

The concrete technical scheme that the present invention takes is as follows:

Based on a timing circuit for 555 integrated chips, this circuit is made up of prime impulse wave circuit for generating and rear class timing circuit, and described prime impulse wave circuit for generating and rear class timing circuit all adopt 555 integrated chips to build.

In prime impulse wave circuit for generating, 4 pin and 8 pin of 555 integrated chip U1 connect+5V power supply, and 2 pin are connected with 6 pin, 1 pin ground connection; One termination+5V the power supply of resistance R1, one stiff end of another termination adjustable resistance RV1, the negative pole of another fixing terminating diode D2 of adjustable resistance RV1, the positive pole of diode D2 connects one end of electric capacity C1, the other end ground connection of electric capacity C1, the adjustable side of adjustable resistance RV1 connects 7 pin of chip U1 and the positive pole of diode D1, and the negative pole of diode D1 connects the positive pole of diode D2 and 2 pin of chip U1; 3 pin of chip U1 connect the positive pole of diode D3, the negative pole access rear class timing circuit of diode D3.

In rear class timing circuit, 4 pin and 8 pin of 555 integrated chip U2 connect+5V power supply, a termination+5V power supply of resistance R2, one end of another termination K switch 1, the other end ground connection of K switch 1, the connecting line between resistance R2 and K switch 1 is also connected with 2 pin of a branch road access chip U2; The diode D3 negative pole of the one termination prime impulse wave circuit for generating of resistance R3, one end of another termination capacitor C2, the other end ground connection of electric capacity C2, the connecting line between resistance R3 and electric capacity C2 is also connected with 6 pin and 7 pin of a branch road access chip U2,3 pin of chip U2 are as output end vo.

Circuit of the present invention adopts 555 integrated chip composition prime impulse wave circuit for generating and rear class timing circuits, and the RC Resistor-Capacitor Unit of impulse wave to rear class timing circuit exported by prime impulse wave circuit for generating charges, therefore the timing of circuit of the present invention is except depending on RC time constant, also depend on the duty ratio of impulse wave, duty ratio due to this impulse wave circuit for generating is adjustable, the duty ratio of impulse wave is less, then timing is longer.Under identical RC time constant, timing can be improved by reducing the duty ratio of impulse wave, so compared with timing circuit form with traditional 555 integrated chips, circuit of the present invention can time regularly longer, the needs of more multi-control occasion can be met.

Accompanying drawing explanation

Fig. 1 is circuit diagram of the present invention.

Embodiment

Below in conjunction with accompanying drawing, the present invention will be further described.

As shown in Figure 1, this timing circuit based on 555 integrated chips is made up of prime impulse wave circuit for generating and rear class timing circuit, and described prime impulse wave circuit for generating and rear class timing circuit all adopt 555 integrated chips to build.

When this circuit uses, in rear class timing circuit, K switch 1 is starting switch, and usual output end vo is low level, the electric discharge pin 7 pin conducting of chip U2, electric capacity C2 no-voltage; After pressing K switch 1, output end vo is high level, the electric discharge pin 7 pin not conducting of chip U2 simultaneously, start to charge to electric capacity C2, when electric capacity C2 charges to 2/3 of supply voltage, output end vo output low level, timing completes, the electric discharge pin 7 pin conducting of chip U2 simultaneously, electric capacity C2 is discharged, for timing is prepared next time.

Different from usual circuit, resistance R3 not connects power end, but connects the output of prime impulse wave circuit for generating.The prime impulse wave circuit for generating built by chip U1 is the adjustable impulse wave circuit for generating of a duty ratio, regulates adjustable resistance RV1, can the duty ratio of regulating impulse ripple.Be impulse wave due to what charge to electric capacity C2 through resistance R3, the rate of climb of the charging voltage of electric capacity C2 is except depending on the time constant of R3C2, and also depend on the duty ratio of impulse wave, the duty ratio of impulse wave is less, and timing is longer.Under the time constant of identical R3C2, timing can be improved by the duty ratio reducing impulse wave.

Claims

1. based on a timing circuit for 555 integrated chips, it is characterized in that: this circuit is made up of prime impulse wave circuit for generating and rear class timing circuit, described prime impulse wave circuit for generating and rear class timing circuit all adopt 555 integrated chips to build;

In prime impulse wave circuit for generating, 4 pin and 8 pin of 555 integrated chip U1 connect+5V power supply, and 2 pin are connected with 6 pin, 1 pin ground connection; One termination+5V the power supply of resistance R1, one stiff end of another termination adjustable resistance RV1, the negative pole of another fixing terminating diode D2 of adjustable resistance RV1, the positive pole of diode D2 connects one end of electric capacity C1, the other end ground connection of electric capacity C1, the adjustable side of adjustable resistance RV1 connects 7 pin of chip U1 and the positive pole of diode D1, and the negative pole of diode D1 connects the positive pole of diode D2 and 2 pin of chip U1; 3 pin of chip U1 connect the positive pole of diode D3, the negative pole access rear class timing circuit of diode D3;