JPH061896B2 - Optical switch device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an optical switch device using a light emitting element and a light receiving element.

(Prior Art) Switch devices include a contact-type switch 10 as shown in FIG. 8 (a) and a non-contact-type switch 20 as shown in FIG. 8 (b).

In the contact type switch 10, the movable contact 10a is the fixed contact 1
By selecting any one of 0 ₁ to 10 _n , the signal on the fixed contact 10 a side can be transmitted to the movable contact side. The non-contact switch 20 emits light when a signal is supplied to the light emitting element 20a, and when this light irradiates any _{one of the} phototransistors 20 _{1 to} 20 _n, an output is obtained from the transistor. Is made in.

(Problems to be Solved by the Invention) In a non-contact type switch, external light input to a phototransistor becomes a problem. Therefore, in order to prevent malfunction, usually, means for shielding external light by an external shield component is provided.

FIG. 9 shows operation waveforms of the optical switch device. The figure (a) is a signal supplied for the light emitting element 20a to emit light, and the figure (b) is opposed to the phototransistor (eg, the phototransistor 20 ₁ as shown in FIG. 8) to be switched. It shows the period to do. 9C shows the output of the phototransistor 20 ₁ , and FIG. 9D shows a sampling clock for sampling the phototransistor 20 ₁ . In the example of FIG. 9, there is no disturbance in the output of the phototransistor 20 _1, and the sampling data at a normal position (FIG. (E)) is obtained.

FIG. 10 shows the output of the phototransistor when there is a disturbance. In this case, due to the disturbance, the data is sampled at an unnecessary position as shown at the first timing of the sampling clock.

The optical switch device may malfunction due to ambient light as described above. Therefore, it is necessary to completely shield ambient light from the outside, and an expensive shielding device is required. However, the shielding device is not always perfect and may be damaged. In such a case, there is no problem if it can be repaired immediately, but it may be difficult to repair depending on the mounting location.

Therefore, an object of the present invention is to provide an optical switch device that is not easily affected by ambient light and has high reliability.

[Structure of the Invention] (Means for Solving the Problems) The present invention supplies a clock having a frequency higher than that of a switch pulse to the light emitting element in order to drive the light emitting element,
The output pulse of the phototransistor sensitive to the light emitting element is counted by the counting means within a predetermined logic level period of the switch pulse. Then, the determination means determines the switch output only when the count value of the counting means is equal to or larger than a predetermined value.

(Operation) By the means described above, even if the output of the phototransistor is disturbed by ambient light, it is possible to determine whether the switch is on or off by the number of pulses of high frequency, so that malfunction can be prevented. This is because the output of the phototransistor due to ambient light can be clearly distinguished from the pulse.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, in which the light emitting element 31 is
It is driven by the burst signal from the control circuit 30. The burst signal is a pulse having a high frequency and is periodically output when switch information is required (see FIG. 4 (a)). Light emitted from the light emitting element 31 is given to any of the phototransistors 40 ₁ to 40 _n . A common bias power supply V _cc is applied to the collectors of the phototransistors 40 ₁ to 40 _n , and the emitters of the phototransistors 40 ₁ to 40 _n have resistors R ₁ and R ₁ , respectively.
It is grounded via R _n and connected to the OR circuit 51. The output of the OR circuit 51 is supplied to the clock of the counter 52. The counter 52 counts the input clock and outputs a count-up output (UP) when a clock having a predetermined value (m) or more is input to the AND circuits 50 ₁ to 50 _n.
Supply to. As a result, the AND circuits 50 ₁ and 50 _n
Makes the outputs from the phototransistors 40 ₁ to 40 _n conductive, and supplies the outputs to the latch circuit 53. The latch circuit 53 latches the input data by the latch pulse LP from the control circuit 30. In addition, the control circuit 30
The gate signal GP is output during the switch output detection period and is supplied to the counter 52 via the inverter 54. Counter 52 is enabled on the leading edge of the gate signal and reset on the trailing edge.

One embodiment of the present invention is constructed as described above, and FIGS. 2 to 4 show its operation waveforms.

In FIG. 2, FIG. 2A shows a gate pulse GP which is output from the control circuit 30 and a burst signal is output in synchronization with this. Therefore, the light emission output from the light emitting element 31 is as shown in FIG. FIG. 2 (c) shows
This shows the ON period of the switch, and shows the state in which the phototransistor 40 ₁ is selected as shown in FIG. 1, for example. FIG. 2D shows the output of the phototransistor 40 ₁ which is output in synchronization with the light emission output. This output is counted by the counter 52. And the counter 52
Is a count-up output UP when counting a predetermined value (m)
Is output (FIG. 2 (e)). As a result, the AND circuit 5
0 ₁ can derive the output of the phototransistor 40 ₁ and supplies it to the latch circuit 53. Here, the latch pulse LP from the control circuit 30 is supplied to the latch circuit 53. Therefore, the latch circuit 53 includes the AND circuit 5.
The output from 0 ₁ , that is, the output from the phototransistor 40 ₁ can be latched. The latch data of the latch circuit 53 is read by the control circuit 30.

FIG. 3 shows an enlarged part of the period T in FIG. That is, the counter 52 is enabled at the leading edge of the gate pulse GP and starts counting the phototransistor output. When the value reaches m, the count-up output UP
Is output and is reset at the trailing edge of the gate pulse GP.
Although the count-up output UP of the counter 52 is used for the gate of the NAND circuit in the above description, basically, a determination means for decoding the contents of the counter 52 may be used.

FIG. 4 shows another example of the operation timing of this embodiment.

This example shows an example in which ambient light is incident on the phototransistor 40 ₁ in the state shown in FIG. In this case, the output of the phototransistor 40 ₁ becomes, for example, the portion X shown in FIG. 4 (4c), and the pulse may be masked. When such a situation occurs, the counter 5
Counter 52 with threshold level VTH of 2
The pulse to be actually counted is, as shown in FIG. 4 (4d), the count value is insufficient and the count-up output UP is lost.

In order to prevent this, as shown in FIG. 5, a separation circuit 60 that separates the low frequency component pulse and the high frequency component pulse.
Is provided on the input side of the counter 52 to solve the problem. That is, the signal of the input unit 701 is supplied to the comparator 7 via the integrating circuit including the resistor 702 and the capacitor 703.
04, and also directly to the other input of the comparator 704. Thereby, the comparator 704
The signals A and B input to the circuit are as shown in FIG. That is, the low-frequency component (disturbance component) is extracted by the integrating circuit, and the comparator 704 acts as a subtraction element for the original signal.
As a result, the output C of the comparator 704 becomes only the high frequency component, that is, the pulse, as shown in FIG.
The pulse to be input to is not masked due to the disturbance component.

The present invention is not limited to the above embodiments. FIG. 7 shows another embodiment of the present invention. The difference from the embodiment of FIG.
It is a means for generating P. That is, the output of the OR circuit 51 is
It is supplied to the monostable multivibrator 80. As a result, the monostable multivibrator 80 outputs a pulse for a fixed period as the first pulse from the OR circuit 51, and this pulse is supplied to the counter 52 via the inverter 54. The other parts are the same as those in the previous embodiment and are therefore given the same reference numerals as in FIG. The gate pulse GP in this case may respond even when noise is output from the OR circuit 51. Therefore, for example, as shown in FIG.
Is set to T'for a longer period. However, if the separation circuit 70 shown in FIG. 5 is connected to the output part of the OR circuit 51, the period T ′ may be substantially the same as T without causing any problem.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a highly reliable optical switch that is hardly affected by ambient light.
In addition to this, the means for shielding the disturbance may be an inexpensive and simple type. Further, even if the shielding means is damaged, the rate of malfunction can be reduced.

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing an embodiment of the present invention, FIGS. 2 to 4 are operation waveform diagrams shown for explaining the operation of the apparatus of FIG. 1, and FIG. 6 is a diagram showing a part of the circuit in the embodiment of FIG. 6, FIG. 6 is a diagram showing an example of signal waveforms of respective parts of the circuit of FIG. 5, FIG. 7 is a diagram showing still another embodiment of the present invention, and FIG. FIG. 9 and FIG. 10 showing an example of a conventional switch device are operation waveform diagrams shown for explaining the operation of the conventional optical switch device. 30 ... control circuit, 31 ... light emitting element, ₄₀ 1 to 40 n _... phototransistor, ₅₀ 1 to 50 n _... AND circuit, 51
... OR circuit, 52 ... Counter, 70 ... Separation circuit, 80 ...
Monostable multivibrator.

Claims (1)

[Claims] 1. An optical switch device in which a light emitting element and a phototransistor are opposed to each other and switch information is obtained by detecting a change in the output of the phototransistor, wherein a high-speed high-frequency clock for driving the light emitting element is preset. Driving means for supplying to the light emitting element during the switch output detection period, counting means for supplying output of the phototransistor receiving light emitted from the light emitting element and capable of counting output pulses of the phototransistor; A timer means for defining a pulse counting period in the counting means from a time corresponding to the first output pulse; and a judging means for judging only the count value of the counting means as a switch output as a switch output. Characteristic optical switch device.