JPH026680Y2 - - Google Patents

Description

[Detailed description of the invention] (Industrial field of application) This invention relates to an accidental activation prevention circuit for aircraft-mounted equipment, etc.

(Prior Art) Unintentional activation of aircraft-mounted equipment due to erroneous input signals, etc. may lead to serious accidents and must be avoided at all costs. For this reason,
Conventionally, the circuit shown in FIG. 3 has been used to block input noise caused by contact chatter, etc., convert it into a regular input signal, and apply it to the equipment. The operation will be explained using the time chart shown in FIG. The one-shot circuit detects the rising timing of the input signal a (including noise) and generates a negative pulse signal b that is synchronized with it and has a constant width determined by the time constant of R-C.
generate. The time delay circuit causes a slight time delay and generates a time delay signal d of the input signal a. The negative pulse signal b from the one-shot circuit and the slightly delayed signal d are subjected to an AND operation by an AND circuit, and pulse-shaped input signals within a certain width of the negative pulse output are considered to be noise and removed. , producing the output signal e shown. That is, noise signals caused by chatter of relay contacts, etc. are removed, and since the time delay circuit is provided, there is no need to consider problems such as generation of whisker pulses due to timing deviations during AND operations.

(Problem to be solved by the invention) By the way, in the case of the above-mentioned conventional example, it is easy to remove the noise at the rise and fall of the input signal due to chattering, etc. ) cannot be deleted and will instead be enlarged. That is, when the input signal a is momentarily interrupted in the middle and has a slit as shown in FIG. 5, the output b of the one-shot circuit generates a negative pulse signal even at the rising timing of the slit. Therefore, the slit of the output e, which is the AND operation of the signal b and the delayed signal d which has passed through the time delay circuit of the input signal a, is rather widened. As a result, the device can prevent unintentional activation at the rise and fall of the input signal, but if there is a momentary interruption in the middle of the input signal, it will be determined that the input signal has been applied twice, and unintentional activation in the middle of the signal will occur. is unavoidable.

(Means to solve the problem) Fill in the slits caused by instantaneous interruptions in the middle of the input signal, eliminate noise at the rise and fall,
This eliminates the risk of unintentional activation of equipment mounted on aircraft, and is characterized by an extremely simple configuration that simply adds a one-shot circuit and an OR circuit to the conventional circuit.

A block diagram is shown in FIG. 1, and a time chart is shown in FIG. 2, and a detailed explanation will be given below.

One-shot circuit A detects the fall timing of input signal a, and synchronizes it with R ₁ −C ₁
A negative pulse signal b having a width determined by the time constant of is generated and used as an input signal to the next one-shot circuit B, and its inverted signal C is used as one input signal of the OR circuit. One-shot circuit B receives input signal a and negative pulse signal b with a constant width _W1 from previous one-shot circuit A, and at the rising timing of input signal a, negative pulse signal b goes high.
Width determined by R ₂ −C ₂ time constant at level
Outputs a negative pulse signal d of _W2 .

In other words, this negative pulse signal d having a width of _W2 is not generated at the rise of the slit due to a momentary interruption in the input signal, and the slit is in the form of a filled hole. On the other hand, the OR circuit performs a logical OR operation on the inverted signal C of the negative pulse signal b of W1 width of the _one -shot circuit A and the input signal a via the time delay circuit, and eliminates the noise signal at the falling edge of the input signal. and converts the noise signal at the rising edge into a positive pulse signal with a width of approximately _W1 . That is, one-shot circuits A and B
The pulse widths W ₁ and W ₂ of the negative pulse signals b and d are,
The relationship is set as W ₁ + noise signal width < W ₂ , and the output e of the OR circuit and the one-shot circuit B
In the logical product operation by the AND circuit with the negative pulse signal d having a width of W ₂ , as shown by the output signal f, the approximately W ₁ width positive pulse signal of the noise signal at the rising edge of the input signal is eliminated. In other words, noise signals caused by contact chatter at the rise and fall of the input signal can be removed by the conventional one-shot circuit A, time delay circuit, AND circuit, etc., and slits caused by instantaneous interruptions in the middle of the input signal can be removed. Especially one
The hole can be filled by the action of shot circuit B.

(Function) Two one-shot circuits are used to generate pulse outputs with different width values, and the pulse outputs are output for the above constant width even when there is a noise signal at the rise and fall of the input signal, as well as a slit caused by a momentary interruption in the input signal. is maintained at a constant value, and the outputs having a constant width are subjected to logical operations to remove noise signals and slits.

(Inventive idea) With a simple circuit configuration that simply adds a one-shot circuit and an OR circuit to the conventional one, it is possible to eliminate slits caused by instantaneous interruptions in the middle of the input signal, and to eliminate Coupled with the removal of the noise signal at the time of falling, the noise contained in the input signal is completely removed, making it possible to prevent unintentional operation of aircraft-mounted equipment and the like.

[Brief explanation of the drawing]

As for the drawings, Fig. 1 is a block diagram of the embodiment of the present invention, Fig. 2 is a time chart for explaining its operation, Fig. 3 is a block diagram of the conventional example, and Fig. 4 is a block diagram of the embodiment of the present invention.
FIG. 5 is a time chart for explaining the operation. ONE SHOTA……One shot circuit,
ONE・SHOTB……One shot circuit B, OR
...OR circuit, AND...AND circuit.

Claims (1)

[Scope of utility model registration request] A one-shot circuit A detects the fall timing of an input signal and generates a pulse signal with a width of W ₁ in synchronization with it, and receives the above-mentioned pulse signal with a width of W ₁ and the input signal and generates the H of the W _1- width pulse signal. A one-shot circuit B that generates a pulse signal with a width of _W2 which is wider than the width of _W1 and which is synchronized with the rise timing of an input signal between levels;
An OR circuit that performs an OR operation between a signal with a slight time lag via a delay circuit and the previous W ₁ -width pulse signal, an AND circuit that performs an AND operation between this operation result and the previous W ₂ -width pulse signal, What is claimed is: 1. An unintentional activation prevention circuit characterized in that the AND circuit output is used as an output signal.