JPH04213915A - Sensor circuit which can be connected in multiple - Google Patents

Abstract

PURPOSE:To detect a detection signal individually without superimposition of detection signals even in the case of connection of plural sensor circuits and with sure prevention of interaction by devising the sensor circuit even in the case of a single circuit in the sensor circuit for a photoelectric switch and a proximity switch. CONSTITUTION:The sensor circuit consists of a self-oscillation circuit 1 oscillated by using a return line (2) as part of a closed loop, a detection circuit 2 implementing the detection at the oscillation period, and outputs an operation end timing of the oscillation circuit externally, receives an input from other sensor circuit, forms the closed loop singly and the sensor circuits when outputs and inputs of plural sensors are connected sequentially form a closed loop via one return line (2) to drive sequentially the detection circuit.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to sensor circuits such as photoelectric switches and proximity switches.The present invention relates to sensor circuits such as photoelectric switches and proximity switches.The present invention relates to sensor circuits such as photoelectric switches and proximity switches. Related to circuits.

0002

2. Description of the Related Art In sensors such as photoelectric switches, a sensor circuit is driven at regular intervals to obtain a detection signal. When a single sensor is used, its operation is performed at regular intervals, but when multiple sensors are used at the same time, the detection timing of each sensor must be staggered to prevent mutual interference. Further, when using a plurality of sensors, it is necessary to wire a pair of power supply lines and a detection line for each sensor, but wiring a large number of lines is very complicated.

Therefore, when a photoelectric switch uses a fixed length range as a detection area, a so-called multi-optical axis sensor is used, which is a structure in which multiple elements are housed in a single case and connected. There are limitations.

0004

As described above, in the past, the devices used were different depending on whether a single sensor was used or when multiple sensors were used simultaneously, so this sensor was not suitable for general use. Furthermore, since the length and number of connections of the multi-optical axis sensor are predetermined, it is not possible to set a free length range as a detection area, and there is a drawback that it is not suitable for detailed handling.

[0005] Therefore, in order to enable the use of a single sensor or a plurality of sensors connected, a separately provided controller is equipped with a counter and a shift register, and the detection time is divided according to the number of sensors. However, the number of connectable sensors is regulated by the counter cycle and division time, and there is a problem in that it is not possible to freely connect any number of sensors.

[0006] In view of these circumstances, the inventor of the present invention has devised a system in which a sensor can be used alone, and any number of sensors can be freely connected, and in such a case, mutual interference can be reliably prevented. The object of the present invention is to provide a sensor circuit that can extract detection signals from all sensors.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the circuit of the present invention includes a self-excited oscillation circuit that oscillates the return line as part of a closed loop, and a detection circuit that performs a detection operation at this oscillation cycle. , consisting of an external output section that outputs the operation end timing of the oscillation circuit, and an external input section,
When used alone, the closed loop is formed; however, when the output section and the input section of a plurality of sensors are sequentially connected, the plurality of sensors form a closed loop via the return line, and the detection circuit is sequentially driven. When connecting a plurality of sensors, a method was used in which a common return line was used to directly connect the external output section and the external input section of the next-stage sensor circuit in sequence.

[0008]

[Operation] The self-excited oscillation circuit forms a closed loop via a return line, and when used alone, performs the function of periodically repeating driving based on this circuit constant. In addition, when multiple sensors are connected, each sensor circuit postpones driving the detection circuit, and when the last sensor circuit finishes driving, a loop is created in which the signal is returned to the first sensor circuit via the return line. Configure. That is, when connected, a large closed loop is formed by the series state of these sensor circuits and the return line, and a periodic detection action is performed. The external output section and the external input section perform the function of connecting the respective sensor circuits in series.

[0009]

[Embodiment] Hereinafter, one embodiment of the sensor circuit of the present invention will be described in detail with reference to the attached drawings. Fig. 1 shows an example in which the inventive circuit is used alone, and Fig. 2 shows a configuration in which four sensors are connected in series.
1 is a self-excited oscillation circuit, 2 is a detection circuit that performs a detection operation in response to a drive pulse generated by this self-excited oscillation circuit 1, a is an input terminal, and b is an output terminal. Also, ■ is a detection line for taking out the detection signal generated by the detection circuit 2, ■ is a return line that forms a part of the self-excited oscillation circuit 1 and forms a loop, and ■ and ■ are a pair of power supplies. It's a line.

When this circuit is used alone as shown in FIG. 1, the self-excited oscillation circuit 1 starts oscillating and outputs the signal c to the return line in the middle of one cycle. This signal is fed back to the self-excited oscillation circuit from point c' via the return line, and the operation of driving the self-excited oscillation circuit 1 again is repeated, each time driving the detection circuit 2. Here, since nothing is connected to input terminal a, a signal is output to output terminal b at the end of one cycle without being influenced by the outside, but nothing is connected to the next stage. There is no impact on the outside world. In this way, when the circuit of the present invention is used alone, a loop shown by a dashed line is formed via the return line, and self-sustained oscillation is performed.

On the other hand, when four units are connected and used as shown in FIG. 2, the first stage circuit first performs self-oscillation and drives the detection circuit, and then the second stage circuit External output is performed from output terminal b. This output signal becomes a trigger signal for the operation of the second stage circuit, drives it, performs a detection operation, and further performs a sequential operation of external output to the third stage circuit. It continues and returns to the first stage circuit again in a large loop indicated by a two-dot chain line. In addition, when multiple units are connected, each signal c to the return line acts to pull down the potential of the return line to low, forming a wired OR, and as long as signal c is output from one of the circuits, the trigger signal The drive of other sensor circuits that are not receiving the current is suppressed.

Next, FIG. 3 explains the configuration of FIG. 1 in more detail. The self-excited oscillation circuit 1 is composed of an oscillation section 3, an input section 4, and an output section 5.
It outputs a signal c to the sensor circuit, and also outputs a trigger to start driving to the next stage sensor circuit.

FIG. 4 shows a specific circuit diagram of the circuit of the present invention. Reference numeral 6 denotes a detection circuit that performs a detection operation in response to a drive pulse generated by the circuit, and its output signal is sent to the detection line (2). 7 and 8 are up edge trigger type one-shot timers, and timer 7 has a longer set time. The two timers receive a trigger at the same time, and timer 8 outputs a drive pulse to detection circuit 6, while timer 7 outputs a control pulse to the sensor connected to the next stage, and also outputs a control pulse to the sensor connected to the next stage. A signal c for switching the potential of (2) to either high or low is output. Triggers for the two timers 7 and 8 are generated by the AND circuit 9 by ANDing the potential of the return line (2), the input signal from the sensor connected to the previous stage, and the power supply reset. Here, the potential of the return line (2) is delayed and input to the AND circuit 9 via the delay timer 10. Here, the Q output of the timer 7 is connected to the base of the npn transistor 11, and the potential of the return line (2) is maintained low while one-shot output is being performed. On the other hand, the Q bar output, which is the inverted output of the Q output, is output from the differentiating circuit 1.
2 and the inverter 13 to the output terminal 14, and becomes an input signal for the next stage sensor. 15 is an input terminal for the input signal from the previous sensor, and the inverted signal is input to the AND circuit 9 via the inverter 16.
The input signal becomes a trigger pulse for the delay timer 10 as it is. Note that 17 is a power supply reset circuit.

Next, the relationship among the various parts when the sensor circuit is operated independently will be explained with reference to the timing chart shown in FIG. First, when the power is turned on to make the sensor function, the reset circuit 17 operates and the potential at point f becomes high, and since the return line (2) of the input of the delay timer 10 is high, the output b becomes high. On the other hand, since nothing is connected to the input terminal 15, it is low, and a high potential, which is an inverted potential by the inverter 16, is similarly input to the AND circuit 9. Therefore, the logic of the AND circuit 9 is established, the output g becomes high, and the first triggers are given to the two timers 7 and 8. Then, the detection circuit 6 is activated by the Q output of the timer 8, and a detection signal is outputted to the detection line (2).

On the other hand, since the timer 7 pulls in point c by the Q output that continues for a certain period of time, the potential of the return line (2) becomes low. Therefore, since the potential at point c' also becomes low, the output d of the delay timer 10 becomes low, and the AND circuit is not established and the output g becomes low. On the other hand, Q
Since the bar output remains low, the output terminal 14 is maintained high by the inverter 13 regardless of the presence or absence of the differentiating circuit 12. During this time, the operation of the timer 8 ends, and then the set time of the timer 7 ends. At the end of the period, the Q output switches to low, the potential at point c becomes high, a trigger is given to the delay timer 10 through point c', and the delay timer 10 starts operating after the preset delay time has elapsed. The output d becomes high, and the timer 7 and
The trigger is given to 8.

At the same time, the Q-bar output of the timer 7 returns to high after the set time has elapsed, but is differentiated by the rising edge only after the timer 7 completes its operation, and becomes a sharp-edged short-time pulse. This is then inverted by the inverter 13 and generated at the output terminal 14. The reason why the differentiating circuit 12 is provided here is to always give a high level to the input terminal of the next stage when multiple units are connected, and also to operate the AND circuit 9 by receiving the differentiated low signal. be. Note that the delay timer 10 cancels the differential signal and outputs the output d of the next stage.
performs the function of maintaining high. In this way, when this circuit is used alone, the detection period is determined by the processing time required for the loop of timer 7 → transistor 11 → return line ■ → delay timer 10 → AND circuit 9 → timer 7 again. Become.

Next, a case in which a plurality of sensors are connected and operated will be described with reference to the timing chart shown in FIG. FIG. 6 shows the operation of the sensors located in the second and subsequent stages when connected. The connection is to the output terminal 14 of the previous sensor.
is directly connected to the input terminal 15 of the subsequent sensor, and the collector of each transistor 11 is connected in parallel to one return line (2). As a result, the potential of the return line (2) has a wired-OR relationship, and if the point c of any sensor is low, the return line itself becomes low. First, the element in which the sensor at the rear stage is influenced by the sensor at the front stage is the trigger of the delay timer 10 by the input signal from the input terminal 15 and the potential of the return line (2), but the potential a of the input terminal 15 is always high, Since the output d of the delay timer 10 only momentarily switches to low when a trigger is applied, the output d of the delay timer 10 functions as a delay operation and always maintains a high output. Since the output f from the reset circuit 17 also remains high at all times, the establishment of the logic of the AND circuit 9 depends on the output e from the inverter 16. That is, only the signal a from the input terminal 15 causes the sensors in the second and subsequent stages to function.

By the way, when only one sensor is operated, the potential c of the return line (■) remains high only while the timer 7 is off, but when connected, the timer 7 of either sensor becomes high. Therefore, in theory, one of the transistors 11 is driven to maintain the low level at all times. However, although the hazard signal is generated for a very short period of time required for signal transfer, this effect is avoided by delay processing by the delay timer 10. This functions particularly effectively in the first stage sensor. In this way, a series of operations are completed in the second stage sensor, and by outputting a low potential pulse from the output terminal 16, the connected sensors are driven one after another.

As described above, when the circuit of the present invention is used, the driving of the sensors is sequentially handed over to the sensors at the subsequent stage, and when the sensor at the last stage completes its operation, the operation is returned to the sensor at the first stage by the return line. Therefore, an arbitrary number can be connected, and the detection range is not limited.

Note that in this embodiment, timer 7 and timer 8 are used, and both timers are triggered simultaneously, and timer 8 is triggered simultaneously.
Although the set time is shorter than that of timer 7, the configuration is not limited to this. That is, since the set time of the timer 7 determines the processing time required for this sensor circuit, if the configuration is such that the driving of the detection circuit 6 can be completed within this time,
For example, the timer 7 may be a two-stage trigger timer, or the timer 8 may be a delay timer.

Further, in this embodiment, for example, the detection signal is taken out as a common detection line as shown in FIG. Of course, the sensor circuit of this embodiment can operate as described above even if the lines are not shared.

[0022]

[Effects of the Invention] Since the circuit of the present invention has the above-described configuration, it is theoretically possible to connect and serially control an infinite number of sensors without the need for a separate controller. When the operation of the first sensor is completed, the potential of the return line causes the sensor at the frontmost stage to return to operation again, forming a loop, so as long as power is supplied, it will continue to operate reliably forever. This makes it possible to create sensor circuits that are ideal for automatic detection systems.

Furthermore, even when used alone, since a self-loop is constructed by the sum of the set times of the one-shot timer and the delay timer, it can be used either alone or in conjunction without changing the circuit at all. This made it possible to create a sensor circuit with extremely wide versatility.

[Brief explanation of the drawing]

[Figure 1] Block diagram when the sensor circuit of the present invention is used alone

[Figure 2] Block diagram when four sensor circuits of the present invention are connected

[Figure 3] A more detailed block diagram of the sensor circuit in Figure 1.

FIG. 4: Detailed circuit diagram of the sensor circuit of the present invention

[Figure 5] Timing chart when the sensor circuit of the present invention is used alone

FIG. 6 is a timing chart of the second and subsequent stage sensor circuits in FIG. 2;

[Explanation of symbols]

1 Self-excited oscillation circuit 2 Detection circuit ■ Return line

Claims (1)

[Claims] Claim 1: A self-excited oscillation circuit that oscillates a return line as part of a closed loop, a detection circuit that performs a detection operation in this oscillation cycle, an external output section that outputs the timing at which the operation of the oscillation circuit ends, and an external input. When used alone, they form the closed loop; however, if the output parts and input parts of multiple sensors are connected in sequence, the plurality of sensors form a closed loop via the return line, which sequentially drives the detection circuit. A multi-connectable sensor circuit characterized by: