JPH03236285A - Photointerrupter with hysteresis having small number of terminals - Google Patents

Abstract

PURPOSE:To provide shaping function of an output waveform of a signal detected from a photodetection output by connecting a light emitting element to a photodetector in series to form a positive feedback circuit, and connecting a bypass circuit for limiting a value to be self-recovered to the photodetector in a negative direction in parallel. CONSTITUTION:A light emitting element 2 like a light emitting diode LED and a photodetector 3 like a phototransistor P.Tr mounted oppositely at a predetermined interval are connected in series to form a positive feedback circuit, a predetermined light emitting current is supplied to the element 2, and a bypass circuit 4 made of a constant-current circuit for limiting a value to be self-recovered to the element 3 in a negative direction is connected in parallel with the element 3. Thus, a switch mechanism having excellent switching characteristic and small erroneous operations including chattering, etc., can be formed. Further, the number of terminals can be reduced, an assembling is facilitated, and the cost of an apparatus can be reduced.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is a switch with hysteresis that can be used for the same purpose in place of switches with electrical contacts used in various consumer and industrial fields. This invention relates to a photointerrupter with a small number of terminals.

(Prior Art) Conventionally, the photointerrupter 12 has a light emitting diode LED and a phototransistor P-Tr installed facing each other as shown in FIG. The received light output generated by the phototransistor P-Tr is projected onto the phototransistor P-Tr, and the received light is detected by an appropriate circuit connected to the load, amplified, and used as a start signal to indicate the switch/ON state to the load. On the other hand, a shielding material 13 made of a suitable material is inserted in the optical path between the light emitting diode LED and the phototransistor P4'r to block light, and the light reception output of the phototransistor P-Tr is reduced to 0. The switch is configured to form a circuit that turns the switch off when the load is turned off, so that it performs the same function as a conventional switch.

This switch mechanism using the photointerrupter 12 has no electrical contacts unlike conventional switches, and therefore has an extremely low frequency of failure.

(Problems to be Solved by the Invention) The photointerrupter 12 described above has the advantage of not having electrical contacts that frequently fail unlike conventional switches, but on the other hand, it requires power to be supplied to the light source from a place where the light source is located. Furthermore, since a signal processing circuit for processing the light output of the phototransistor P-Tr is also required, there are disadvantages such as an increase in the number of wiring lines compared to conventional switches.

Further, the conventional photointerrupter 12 has a light emitting diode L.
It functions as a switch by opening and blocking the optical path between the ED and the phototransistor P-Tr with the shielding material 13. When the optical path is blocked from the shielding material No. 13, the phototransistor P-Tr Since the output of the signal that detects the light receiving output of the Tr gradually decreases, there is also a drawback that the switching characteristics are poor when a switch mechanism is formed.

(Means for Solving the Problems) The present invention has been made by focusing on the above-mentioned problems in the conventional art. Functions such as shaping the output waveform of the signal that detects the received light output (hereinafter referred to as the received light output signal) by connecting the The purpose of the present invention is to solve the above-mentioned problems by providing a photointerrupter that can have the following characteristics.

The present invention is characterized in that a light emitting element and a light receiving element are connected in series to form a positive feedback circuit, and a bypass circuit is connected in parallel to the light receiving element to limit the self-returnable value in the negative direction. This is a photointerrupter with a small number of terminals and hysteresis.

(Function) The photointerrupter has extremely good switching characteristics and can form a switch mechanism with less malfunction including chattering.

Furthermore, since the photointerrupter has hysteresis and has the function of shaping the output waveform of the light reception output signal, it simplifies a complicated waveform shaping circuit and simplifies the circuit of the device.

Furthermore, since the photointerrupter can have fewer terminals than conventional ones, it is easy to assemble it as a device.

Furthermore, since the photointerrupter has a simple structure, it is extremely easy to manufacture, and since no special parts are used, mass production is easy.

(Example) The present invention will be described in detail below based on an example shown in FIGS. 1 to 3. In FIG. 1 showing the basic circuit of a photointerrupter 1, a light emitting element 2 such as a light emitting diode LED and a light receiving element 3 such as a phototransistor P-Tr are connected in series, and are placed facing each other at a required interval. A bypass circuit 4 consisting of a constant current circuit that forms a positive feedback circuit, supplies a required light emitting current to the light emitting element 2, and limits the value that the light receiving element 3 can self-return to in the negative direction is connected to the light receiving element. 3 are connected in parallel. The conventional three or more output terminals are reduced to two.

As shown in the figure, the constant current circuit consists of a resistor and a diode connected in series, and a transistor connected in series (the base is connected in parallel to the midpoint between the resistor and the diode (connection) and the resistor is connected in parallel).

The functional action of this photointerrupter 1 is
The following description will be made using an apparatus in which a power source 6 is inserted, with the ○ side connected to the light-receiving element 3 and the ○ side connected to the light-emitting element 2, respectively. First, a predetermined current (emission current) generated by a constant current circuit, which is a bypass circuit 4, flows through the light emitting element 2 and causes it to emit light, and this light enters the light receiving element 3, forming an optical path between them. , a light receiving output is generated at the light receiving element 5.

Next, since the photocurrent generated by the light reception output flows through the light emitting element 2 together with the light emitting current, the amount of light emitted by the light emitting element 2 increases, and this increased light amount enters the light receiving element 3, so that the light receiving element 3 The photocurrent will also increase. By repeating this phenomenon, the photocurrent gradually increases, and as it is limited by the connected load 5, the current increases in an avalanche manner until it reaches a saturated state.

From this, when the optical path is blocked by the shielding material 7, the current flowing to the load is only the light emitting current generated by the bypass circuit and set to a minute value, and the shielding material 7 moves and the optical path is blocked. Once formed, it will increase rapidly as described above. If the formed optical path is again interrupted, the above operation will be reversed and the current will be rapidly attenuated.

For these reasons, the photointerrupter 1 has hysteresis and has the function of shaping the output waveform of the light reception output signal generated in the light receiving element 3.

The data obtained by actually measuring the change in the light receiving output signal when the optical path is opened and closed by moving the shielding material 7 between the light emitting diode LED, which is the light emitting element 2, and the phototransistor P-Tr, which is the light receiving element 3, is shown in the third table. As shown in the figure.

Note that A is a photointerrupter 1 according to the present invention, and B is a conventional photointerrupter. In addition, the experiment was conducted using the same experimental equipment, with the power supply voltage applied to both photointerrupters A and B and the value of the load 5' inserted into the circuit being the same, so that the output of the light receiving output signal was changed to the load 5'. The condition was that the temperature was sufficiently saturated.

According to the data shown in FIG. 3, in the case of the conventional photointerrupter B, when the shielding material 7 is pulled down to block the optical path, the blocking area becomes large (because of the problem that occurs in the phototransistor P-Tr). The output voltage of the light reception output signal gradually decreases, but in the case of the photointerrupter according to the present invention, even if the optical path blocking area increases, the output voltage of the light reception output signal does not decrease and remains linear. When the optical path is completely blocked, the received light output drops linearly to 0.This phenomenon is mainly caused by the
This is thought to be due to the formation of a positive feedback circuit, and this characteristic represents the optimum state for the switching function.

In addition, when the shielding material 7 that blocked the optical path is pulled up so that the optical path is opened, in the case of photointerrupter B, the output voltage of the light reception output signal rides on the voltage change curve when the optical path was interrupted. increases gradually as the shielding material 7 opens, but in the case of the photointerrupter A, the output voltage of the light reception output signal does not rise until the photocurrent from the phototransistor P-Tr reaches a predetermined value. When it reaches , it moves linearly horizontally following the voltage change curve when it rises and blocks the optical path.

The photointerrupter A clearly has a so-called hysteresis characteristic, and the phototransistor P-
It has a function of shaping the output waveform of the light reception output signal generated in the Tr.

In this case, the photointerrupter A has extremely good switching characteristics and can form a switch mechanism with less malfunction including chattering.

Furthermore, since the photointerrupter 1 has hysteresis and has a function of shaping the output waveform of the light reception output signal, a complicated waveform shaping circuit can be simplified, and the circuit of the device can be simplified.

Furthermore, the photointerrupter 1 can be easily assembled as a device because the number of terminals can be reduced compared to conventional ones.

Furthermore, the photointerrupter 1 has a simple structure, so it is extremely easy to manufacture, and since no special parts are used, mass production is easy.

Taking into account the above embodiment, the photointerrupter 1 is
A light emitting diode LED is used as the light emitting element 2.

Although the phototransistors P-T'r are used as the light-receiving elements 3, other elements may be used instead of the light-emitting diode LED and the phototransistor P-Tr as long as they have functions equivalent to both.

Further, the photointerrupter 1 uses a constant current circuit as the bypass circuit 4, but instead of this constant current circuit, as shown in FIG. Figure 4-port) or three-terminal regulator 1
0 (Fig. 4-8) may be used.

Further, the photointerrupter 1 can form a photointerrupter 1' that can suspend the received light output signal by disconnecting the connection point of the bypass circuit 4 and providing a reset terminal 11 that leads to an external connection terminal, as shown in FIG. .

In this photointerrupter 1', a light emitting current is caused to flow through the light emitting element 2 from the reset terminal 11 through the bypass circuit 4 to bring it into a normal operating state.

(Effect of the invention) Since the present invention has the above configuration, it has the following effects.

(1) It is possible to form a switch mechanism with extremely good switching characteristics and less malfunctions including chattering, thereby satisfying the needs of customers.

(2) The circuit has a function of shaping the output waveform of the signal that detects the received light output with hysteresis, which simplifies the shaping circuit and reduces the number of terminals, making assembly easier. This makes it easy to reduce the cost of equipment.

(3) Since the structure is simple, it is extremely easy to manufacture, and since no special parts are used, mass production can be planned. Combined with the above (2), it can be provided to customers at low cost. .

(4) The above items work together to increase sales and contribute to increasing corporate profits.

[Brief explanation of drawings]

Figures 1 to 3 show one embodiment of the present invention. Figure 1 is a basic circuit diagram, Figure 2 is a partially simplified circuit diagram for explaining the function, and Figure 3 is a shielding material for the optical path. Figure 4 is a partially simplified circuit diagram showing another example of a bypass circuit, and Figure 5 is a basic circuit. FIG. 6 is a partially simplified circuit diagram showing another example in which a reset terminal is provided in the conventional photointerrupter. 1.1... Photo ink converter 2... Light emitting element 3... Light receiving element 4...
Bypass circuit 5, 5...Load 6...Power supply
7... Shielding material 8... Resistance
9...Low current diode 10...Three terminal regulator P-Tr...Phototransistor LED...Light emitting diode

Claims (4)

[Claims] (1) A hysteresis system characterized by connecting a light emitting element and a light receiving element in series to form a positive feedback circuit, and connecting the light receiving element in parallel with a bypass circuit that limits the self-returnable value in the negative direction. A photo interrupter with a small number of terminals. (2) The photointerrupter according to claim 1, wherein the light emitting element is a light emitting diode and the light receiving element is a phototransistor. (3) The photointerrupter according to claim 1 or 2, wherein the bypass circuit is constituted by a constant current circuit. (4) The photointerrupter according to claim 1 or 2, wherein the bypass circuit is composed of a resistor, a constant current diode, or a three-terminal regulator.