JPS607415B2 - detection switch - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a detection switch such as a photoelectric switch or a proximity switch.

In general, detection signals from detection switches such as photoelectric switches and proximity switches are often sent to control equipment that outputs electrical or mechanical signals, so the detection signals are subject to temporal processing depending on the detection purpose and conditions. A timer circuit is often required.

For example, there are the following examples when detecting a passing object on a conveyor. '1} When objects of different sizes are passing and you want the detection output of only a large object, or when you want to detect when an object is stuck and has stopped, use the detection switch to detect the object. It is necessary to perform a so-called on-delay operation in which an output signal is output a certain period of time after a signal is input.

[21 If you want to know when a detection object of the same shape is missing when it passes continuously at a fixed interval, the output signal will be detected after a fixed period of time after the object detection signal from the detection switch disappears. A so-called off-delay operation is performed. In this case, a state in which there is no output signal is a missing signal. Rigid If you want to pull the solenoid for a certain amount of time or stop the conveyor from the moment an object is detected, perform a one-shot operation. As in the several examples above, various timed operations were required in actual use, and various types of control equipment were required.

However, this is complicated in terms of management, and a detection switch with a built-in multifunctional timer circuit is desired. SUMMARY OF THE INVENTION An object of the present invention is to provide a detection switch equipped with a multifunctional timer circuit capable of switching time-limited operations such as one-shot, on-delay, and off-delay operations using a built-in switch.

Embodiments of the present invention will be described below based on the drawings.

In FIG. 1, 1, 5, 10, and 11 are exclusive OR circuits (hereinafter referred to as EX-OR) made of C-MOSIC. All of these EX-ORs have high input impedance and low output impedance. One input of EX-OR1, 10 is connected to L level and H level, respectively, EX-ORI operates as a buffer, and EX-ORIO operates as an inverter. Note that C-M061C, in which four EX-ORs are housed in one package, is generally available. This embodiment is a photoelectric switch, and the signal pulse from the photoelectric detection circuit 17 (which emits light from a light emitting element and receives reflected light by a light receiving element and converts it into an electrical signal) is at L level when there is no signal, and when there is no signal, the signal pulse is at L level. The signal is at H level. first,
The case when the switch 15 is closed will be explained.

EX-OR5, regardless of whether switch 16 is opened or closed.
Since one input of 11 is both at L level, EX-
OR5 and 11 operate as buffers. Furthermore, since the switch 15 is closed, the resistor 3 serves as a load for the EX-OR 5, and a CR differential circuit consisting of the capacitor 2 and the resistor 4 is formed. The time constant of this differentiator circuit is timer circuit 1
The time constant is set so small that it can be ignored compared to the time constant of 9. Assume now that a signal pulse with a longer duration is output from the photoelectric detection circuit 17 (see FIG. 2a).

As shown in FIG. 2b, the EX-OR 5 outputs a pulse of positive polarity whose length is determined by the time constant of the differentiating circuit and the threshold voltage V of the EX-OR 5. transistor 7
conducts for time t2, capacitor 9 is charged during time t2, and then when transistor 7 is turned off, the charge in capacitor 9 is discharged through variable resistor 8, so that capacitor 9 and variable resistor The collector potential of the transistor 7 rises with a time constant T caused by the transistor 8. When the threshold voltage V of EX-ORIO is reached, the output of EX-ORIO is inverted, and a signal of length T as shown in FIG. 2d is outputted via EX-ORII. That is, a one-shot pulse of constant length T can be obtained regardless of the length of the input signal.
This length T can be varied by changing the resistance value of the variable resistor 8. Next, a case where both switches 15 and 16 are open will be explained.

Since one input of EX-OR5, 1 on the side to which switches 15 and 16 are connected is connected to the positive power supply line through resistor 12, it becomes H level, so EX-OR5,
11 both operate as inverters. Furthermore, a differential circuit consisting of the capacitor 2 and resistor 4 is not formed. Third
As shown in Figure a, when a signal pulse of length t is output from the photoelectric detection circuit 17, the resistance values of resistors 3 and 4 are EX-
Since it is negligibly small compared to the input impedance of OR5, the output of EX-ORI is directly transmitted to the input of EX-OR5 through resistors 3 and 4, and
5 outputs an inverted pulse as shown in FIG.
The potential increases with a time constant T caused by the variable resistor 8 and the capacitor 9. When the threshold voltage V of EX-ORIO is reached, the output of EX-ORIO is inverted, and the output 18' produces a pulse that rises a certain time L behind the rise of the input signal as shown in FIG. 3d. In other words, the output signal is obtained T2 after the input signal is input. This T
2 is generally called an on-delay time, and such an operation is called an on-delay operation. Finally switch 15
The case where the switch 16 is open and the switch 16 is closed will be explained.

EX-OR6 and EX-OR11 operate as a buffer and no differentiating circuit is formed. When a signal pulse of length L is generated from the photoelectric detection circuit 17 as shown in FIG. 4a, an inverted output as shown in FIG. 4b is generated from the EX-OR5, and as shown in FIG.
As shown in the figure, the transistor 7 is conductive only during the time period, and the collector potential rises with a time constant T after the signal pulse disappears. When the threshold voltage V of EX-ORIO is reached, EX-ORIO is inverted. As a result, a pulse is obtained at the output terminal 18, as shown in FIG. 4d, which falls a certain time T3 later than the fall of the input signal.
This time T3 is called an off-delay time, and such an operation is called an off-delay operation. Although a photoelectric switch has been described in the above embodiment, the present invention can also be applied to other detection switches, such as connecting a high frequency oscillation type proximity detection circuit in place of the photoelectric detection circuit 17 to create a nearby switch. Of course.

As described above, according to the present invention, the three operations of one-shot, on-delay, and off-delay can be switched with one type of detection switch, so there is no need to prepare various types of control equipment, and the circuit configuration is extremely simple. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a photoelectric switch according to an embodiment of the present invention, and FIGS. 2 to 4 are time charts used to explain the circuit of FIG. 1. 1, 5, 10, 11...EX-OR, 3, 4, 6, 12
...Resistor, 2,9...Capacitor, 8...
...Variable resistor, 7...Transistor, 15,1
6... Switch, 13, 14... Diode. Many figures, many 2 figures, many 9 figures, many 2 figures

Claims (1)

[Claims] 1 a detection circuit, a low output impedance buffer amplifier into which the output of this detection circuit is input, and a first and second
an exclusive OR circuit, a capacitor connected between the output of the buffer amplifier and one input of the first exclusive OR circuit, and a plurality of series connections connected in parallel to this capacitor. a first switch connected via a diode between the interconnection point of the resistor and one power supply line, and the other input of the first exclusive OR circuit and the other and a predetermined time constant connected between the output of the first exclusive OR circuit and one input of the second exclusive OR circuit. the other input of the first exclusive OR circuit and the other input of the second exclusive OR circuit are commonly connected, and the timer circuit is connected between this and one power supply line. and a diode connected between one end of the second switch that is not on the power line side and one end of the first switch that is not on the power line side.