JPH01212914A - Signal processing circuit - Google Patents

Abstract

PURPOSE:To detect an object even when the time of an open signal is very short by outputting a signal representing the object detecting state when an interruption signal obtained from a photodetection section of an optical modulation type photo interrupter is inputted consecutively for n-time and returning an output signal into the non-detection state when the open signal is inputted from the photodetection section. CONSTITUTION:When two objects are accessed to a degree of in contact with each other as shown in periods b, c, Q outputs of D flip-flop circuits 1-3 all go to a high level at a point of time when a low level of 3-pulse is inputted from a time t3 as to the object shown in the period (b). Thus, an output of a NAND circuit 5 goes to a low level and an output of a latch circuit 8 goes to a high level to obtain a detection output (f) corresponding to the period (b). Furthermore, the period of the clock pulse is set to a time equal to the minimum time or a gas when two objects pass continuously or shorter than that thereby causing a clock pulse without fail in a period (e). Thus, even when the time of the open signal generated between the objects is very short, mis- detection of the object is not caused.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a signal processing circuit for a photointerrupter that includes a light emitting section and a light receiving section and detects an object passing between the two. The present invention relates to a signal processing circuit for an optical modulation type photointerrupter that pulse-drives a light modulation type photointerrupter.

[Conventional technology]

FIG. 3 shows a signal processing circuit of a conventional optical modulation type photointerrupter, and FIG. 4 shows its operating waveform diagram.

In order to prevent malfunctions caused by fluorescent lamp noise and the like, the light modulation type photointerrupter determines the presence or absence of an object when a pulsed detection signal from the light receiving section is generated multiple times in succession. The signal processing circuit shown in FIG. 3 determines the presence or absence of an object when the same type of detection signal (blocking signal or opening signal) is received three times in a row from a light receiving section (not shown).

In FIG. 3, 1 to 3 are D-type flip-flop circuits;
4 to 7 are NAND circuits. Further, the NAND circuits 6 and 7 constitute a latch circuit (R8-flip-flop circuit) 8. 9 is an input terminal for a clock signal synchronized with the driving pulse of the light emitting section, 10 is an input terminal for a detection signal from the light receiving section, 11 is an input terminal for a preset signal, 1
2 is an output terminal of this signal processing circuit.

Figure 4 (A) shows the output of the light receiving section assuming that the light emitting section is driven by direct current.
, c) indicates that the light emitted from the light emitting section to the light receiving section is blocked, that is, the presence of an object. vice versa,
The high level part shows the open state after the object has passed.

The same figure (B) shows the driving pulse timing of the light emitting part, and the same figure (C
) to (E) are D-type flip-flop circuits 1 to 3, respectively.
The Q outputs of (F) and (G) in the same figure are respectively NAND circuit 4.
．． (H) in the figure shows the output of the latch circuit 8 appearing at the output terminal 12.

The operation will be briefly explained using section a as an example. Input terminal 1
Since the low level has been input for three consecutive pulses from time t1 to 0, the output of the NAND circuit 5 becomes low level at that time, and the output of the latch circuit 8 becomes low level.

Further, three consecutive pulses of high level are input from time t2, and thereby the output of the latch circuit 8 becomes high level. Therefore, the section d from the falling edge to the rising edge of the latch circuit 8 indicates the passage of one object.

[Problem to be solved by the invention]

However, with this conventional circuit, it is not possible to identify objects to be detected when they pass very close to each other to the extent that they touch each other.

For example, sections S and C both indicate the passage of an object to be detected, but since they are very close to each other, an open air occurs between them, as shown in Section e of Fig. 4(A). The time width of the signal is very short.

In such a case, the conventional circuit described above treats the section e as mere noise and cannot detect it. That is, as shown in section f of FIG. 4(H),
It is perceived as a single object.

An object of the present invention is to solve these problems.

[Means to solve the problem]

In order to solve the above problems, the signal processing circuit of the present invention outputs a signal indicating an object detection state when a cutoff signal obtained from the light receiving section of a light modulation type photointerrupter is inputted one time in a row, and detects an object. The output signal is returned to the non-detection state when an open signal is input from the light receiving section under certain conditions.

[Effect]

Since the object detection state is not established unless the cutoff signal from the light receiving section is inputted once in a row, the damping signal of the object generated at the tip of the object can be ignored. Moreover, when an open signal is input from the light receiving unit in the object detection state, the state is immediately returned to the non-detection state, so even if the object passes through the photointerrupter continuously and the time of the open signal generated between the objects is very short, the object cannot be detected. will not fail to detect.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a waveform diagram showing its operation. In addition, in the description of the drawings, the same elements are given the same reference numerals, and redundant description will be omitted. The circuit of this embodiment uses the same components as the conventional circuit shown in FIG. 3, but the connection state between each component is different. To briefly explain the connection of each element, the Q output of the D-type flip-flop circuit 1 is connected to the D input of the D-type flip-flop circuit 2, and the Q output of the D-type flip-flop circuit 2 is connected to the D-type flip-flop circuit 3. Connected to D input. The Q outputs of the D-type flip-flop circuits 1 to 3 are input to the NAND circuit 5.
The NAND circuit 4 receives the Q output of the D-type flip-flop circuit 1 and the Q output of the D-type flip-flop circuit 2.3, and further receives the output of the latch circuit 8 as an enable signal. Note that since the output terminal 12 is connected to the output terminal of the NAND circuit 7, in the circuit of this embodiment,
A high level output signal indicates an object detection state indicating the presence of an object.

Here, the operation of this embodiment will be explained with reference to the waveform diagram of FIG. 2. Figure 4 (A) shows the output of the light receiving unit assuming that the light emitting unit is driven by direct current, and in order to clarify the difference from the conventional technology, the same waveform as in Figure 4 (A) is given. ing. Note that this waveform is obtained when a highly elastic metal sphere passes through a photointerrupter. Figure 2 (B) is the driving pulse timing of the light emitting section, (C) to (E) are the Q outputs of D-type flip-flop circuits 1 to 3, respectively, and (F) and (G) are NAND circuits, respectively. 4.5 output,
(H) in the figure shows the output of the latch circuit 8 appearing at the output terminal 12. Note that (B) to (E) in the same figure are also similar to Fig. 4 (
The waveforms are the same as those in B) to (E).

Regarding the object shown in section a, when three pulses of a low-level input signal (blocking signal) are input from time t1, all Q outputs of D-type flip-flop circuits 1 to 3 are at high level, that is, all 100 outputs are low. level, so the NAND circuit 5 switches from high level to low level. As a result, the output of the latch circuit 8 rises to a high level, indicating that the tip of the object has been detected. When the end of the object passes through the photointerrupter and an open signal is applied to the input terminal 10, immediately after that, at time t2,
The Q output of the D-type flip-flop circuit 1 becomes high level. As a result, all the signals input to the NAND circuit 4, including the enable signal from the latch circuit 8, become high level, and the output of the NAND circuit 4 becomes low level, while the output of the NAND circuit 5 becomes high level. . Therefore, the output of the latch circuit 8 becomes a low level, and the section d of the output signal becomes the detection output corresponding to the section a of the input signal.

Next, consider the case where two objects pass through the photointerrupter so close that they touch each other, as shown in sections c and c. Regarding the object shown in section 2, when the D-type flip-flop circuit 1 receives three pulses of low level (blocking signal) from time t3, the Q outputs of the D-type flip-flop circuits 1 to 3 all become high level. As a result, the output of the NAND circuit 5 becomes low level, and the output of the latch circuit 8 becomes high level.

Subsequently, at time t4, a gap between the two objects indicated by the open signal in section e is detected, and the D-type flip-flop circuit 1
When the Q output of becomes high level, the outputs of NAND circuits 4 and 5 become low level and high level, respectively, and the output of latch circuit 8 falls from high level to low level, similarly to the end of section a. As a result, a detection output f corresponding to the section S is obtained. Note that the period of the clock pulse shown in Fig. 2 (B) is set to a time equal to or shorter than the minimum time of the gap when two objects pass successively, so that A clock pulse is always applied to the .

Regarding section C, the output of the latch circuit 8 is maintained at a low level from time t5 until three pulses of the low level input signal are input, and at the third pulse, the output of the latch circuit 8 becomes high level. Detection of the rear end of section C is performed in sections a and b.
The circuit operates in the same way as at the rear end, and a detection output g is obtained.

In this example, it is assumed that an object is detected when three pulses of the cutoff signal from the light receiving section are input, but the number of pulses is not limited to "3", and the relationship with the damping duration etc. It may be set appropriately in .

〔Effect of the invention〕

As explained above, according to the signal processing circuit of the present invention,
Since the object detection state is not entered unless the cutoff signal from the light receiver is input 0 times in a row, it is possible to ignore the damping signal of the object generated at the tip of the object. Since the sensor immediately returns to the non-detection state upon input of , the object will not be failed to be detected even when the object passes through the photointerrupter continuously and the duration of the open signal generated between the objects is very short.

Therefore, it is possible to accurately count objects that are likely to cause damping due to their strong elasticity and that may pass continuously between the light emitting section and the light receiving section of the photointerrupter.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is an operating waveform diagram thereof, FIG. 3 is a circuit diagram showing a conventional signal processing circuit, and FIG. 4 is an operating waveform diagram thereof. 1-3...D-type flip-flop circuit, 4-7...
NAND circuit, 8... latch circuit, 12... output terminal. Example Fig. 1 Prior art -a--b→-C→ (Day Q3 (G)5

Claims (1)

[Claims] A signal indicating an object detection state is output when a cutoff signal obtained from the light receiving section of the light modulation type photointerrupter is inputted n times in succession, and when an open signal is inputted from the light receiving section under the object detection state as a condition. A signal processing circuit characterized in that the output signal is returned to a non-detection state.