JPH035634B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an input signal control circuit for an alarm circuit when the alarm circuit is driven by an output signal from a sensor section.

For example, in a light beam alarm that detects the passage of an object, a change in a light reception signal of a light receiving section is detected, and if the level of the change is equal to or higher than a predetermined level, an alarm circuit is activated. However, if the instantaneous amount of light emitted changes due to fluctuations in the power supply voltage, or if the reference value of the level detection circuit changes, there is a risk that the alarm circuit will be activated even though no object has passed. Conventionally, in order to absorb fluctuations in the power supply voltage, a capacitor C was connected in parallel to the power supply E to absorb the instantaneous fluctuations in the power supply, as shown in Figure 1A, or a constant voltage circuit was used as shown in Figure 1B. A method using A is known.

However, even in the conventional example shown in Fig. 1 A and B, when the power is restored after a momentary power outage, the sensor section A is connected to the light receiving element, amplification circuit, detection circuit, and level detection circuit as shown in the circuit of Fig. 2. etc., and when capacitors C〓 and C〓 were connected between each circuit, trigger pulse-like noise could occur. However, due to the configuration of the change detection circuit, it is not possible to connect a capacitor C in parallel as shown in Figure 2 to absorb trigger pulse noise. This is because even normal signals are absorbed by the capacitor C.

The present invention has been made in view of the above-mentioned drawbacks, and even in the output of the power supply voltage fluctuation detection circuit,
This invention provides an input signal control circuit that connects only the true signal of the sensor section to the next stage electric circuit by controlling the input of the output signal of the sensor section to the next stage electric circuit. .

In FIG. 3, 1 indicates a sensor section. For example, the sensor section includes a light receiving element 1 as shown in FIG.
a, amplification circuit 1b, detection circuit 1c, integration circuit 1
d, and a level detection circuit 1e. 3 is a power supply voltage fluctuation detection circuit. R ₁ , R ₂ , R ₃ , and _{R 4} are resistors that divide the power supply voltage +Vcc to obtain divided voltages Va, Vb, and Vc at the connection points of each resistor. here
If R ₁ =R ₄ ≫R ₂ =R ₃ , then Vb≈1/2Vcc, as shown in FIG. 5. Comparators 3a and 3b are connected as shown. Note that the capacitor _C3 is a capacitor for suppressing fluctuations in the voltage Vb at the connection point b. Positive pole of power supply and point d
A capacitor C ₁ connected between the two is a capacitor for relating fluctuations in the power supply voltage to fluctuations in the voltage Vd. Capacitor C ₂ is comparator 3
This capacitor is used to extend the recovery time of the voltage Ve when the outputs of a and 3b shift from low level to high level. 2 is an AND gate. 4 is an electric circuit such as an alarm display circuit.

In addition, the sensor 1, the power supply voltage fluctuation detection circuit 3,
The power supply of the AND gate 2 is all set to Vcc. Further, the power supply voltage of comparators 3a and 3b is also set to Vcc.

Therefore, as shown in FIG. 6P, the power supply voltage fluctuates, and the voltage Vd at point d of the power supply voltage fluctuation detection circuit 3
When Vc becomes lower than the voltage Vc at point c, the output of comparator 3b is inverted from the [H] level to the [L] level. Similarly, as shown in FIG. 6Q, when the voltage Vd becomes higher than the voltage Va at point a, the comparator 3
a is inverted from the [H] level to the [L] level.
Therefore, comparator 3a or 3b operates and outputs
When Ve is at the [L] level, the output of the gate section 1 is not input to the electric circuit 4 at the next stage.

In addition, the voltage Vc is a capacitor to prevent voltage fluctuations.
Since _C3 is connected, there is almost no fluctuation in response to instantaneous fluctuations in the power supply voltage as shown in FIG.

Further, although the voltage Va differs from Vc and fluctuates with fluctuations in the power supply voltage, the width of the fluctuation is extremely small compared to Vd.

FIG. 7 shows another embodiment, in which there are two sensor sections 1', 1'', and if the outputs of these two sensor sections 1', 1'' occur simultaneously, the power supply voltage will fluctuate. By connecting the outputs of both sensor sections 1' and 1'' to point c of the detection circuit 3 via the AND gate 5, the power supply of the AND gate 5 is Vcc, so the output of the gate 5 is the power supply voltage Vcc.
By outputting a voltage of [H] level that is approximately equal to , and inverting the input voltages of (+) and (
The comparator 3b is inverted from [H] level to [L] level, voltage Ve is set to low level, and both AND gates 2', 2'' are used to connect the outputs of sensor sections 1', 1'' to the next stage electric circuit. 4' and 4'' are configured so as not to be input.

As described above, according to the present invention, the output signal of the sensor unit is processed through a gate circuit that takes an AND with the output of a power supply voltage fluctuation detection circuit whose output is inverted when the power supply voltage fluctuates in a positive or negative direction within a predetermined width. In an input signal control circuit connected to the next-stage electric circuit, the power supply voltage fluctuation detection circuit divides the power supply voltage using resistors, and detects a reference value and a voltage that is more positive or negative than the reference value using two comparators. At the same time, the reference value side terminal was connected to the power supply via the capacitor C1, and the outputs of the two comparators were connected to form an input signal control circuit that was used as an input for AND, so the power supply voltage fluctuated. In this case, the output signal from the sensor section is not input to the next-stage electrical circuit, which greatly reduces the cause of malfunctions. Moreover, the power supply voltage fluctuation range is set, and if the fluctuation range is exceeded even slightly above or below, the operation is activated.
Highly accurate detection is possible.

[Brief explanation of the drawing]

1 and 2 are block diagrams showing a conventional example of the present invention. FIGS. 3 to 7 are drawings for explaining embodiments of the present invention, and FIGS.
7 and 7 are block diagrams, FIG. 5 is a diagram showing voltage levels, and FIG. 6 is a voltage waveform diagram. 1: Sensor section, 2: AND gate, 3: Power supply voltage fluctuation circuit, 4: Electric circuit.

Claims (1)

[Scope of Claims] 1. The output signal of the sensor unit is passed to the next stage via a gate circuit that takes an AND with the output of a power supply voltage fluctuation detection circuit whose output is inverted when the power supply voltage fluctuates in a positive or negative direction within a predetermined range. In an input signal control circuit connected to an electrical circuit, the power supply voltage fluctuation detection circuit divides the power supply voltage using resistors, and inputs a reference value and a voltage that is more positive or negative than the reference value to two comparators. At the same time, the reference value side terminal is connected to a power supply via a capacitor C1, and the outputs of the two comparators are connected and used as an input for AND.