JPS61193092A - Optical detecting circuit - Google Patents

Abstract

PURPOSE:To decrease the number of interface signal lines to a driving and detecting circuit by varying the quantity of light emission of a light emitting element according to whether or not there is a body between the light emitting element and a photodetecting element. CONSTITUTION:A detection unit 3, the light emitting element 4, the photodetecting element 5, a bias element 6, a Schmitt trigger element 8, etc., are provided. Then, when the unholed part of a disk is at the position of the unit 3, light from the element 4 does not reach the element 5, so an output current IP does not flow. Namely, when the current ID flowing to the element 4 is only a current IR flowing from the element 6, the quantity of light emission is small. Therefore, the input voltage Vi to the element 8 is at a low level and the output voltage V0 from the element 8 is at a high level. Then, the holed part of the disk comes to the position of the unit 3, the light from the element 4 reaches the element 5 and the current IP begins to flow. The element 5 is connected to the element 4 in series, so the quantity of light emission increases and the current IP further increases. This feedback is carried on until saturation is obtained and the output voltage V0 of the element 8 falls to the low level when the saturation is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical sensing circuit, and particularly to an optical sensing circuit that is simple and has a favorable interface.

[Background of the invention]

In order to detect the position of an object in a mechanical part of a terminal device, robot, etc., optical detection elements are often used in place of conventional mechanical switches in order to improve reliability.

As these devices become more sophisticated, the number of locations whose positions must be detected has increased significantly, and the number of drive/detection circuits and interface signal lines has also increased, creating an obstacle to miniaturization of mechanical units.

As a conventional optical detection path, a circuit such as that manufactured by Sharp Corporation is known. In this circuit, the circuit of the 9 light emitting elements and the light receiving element is a circuit that does not increase speed.
Therefore, the circuits for the two light-emitting elements and the light-receiving element are separate circuits for the source, and at least three interface signal lines, power ground and output, are required between the drive and detection circuits. .

Furthermore, the detection circuit requires an amplifier circuit.

[Purpose of the invention]

An object of the present invention is to provide an optical detection circuit in which the number of interface signal lines with the drive/detection circuit is reduced.

[Overview of the invention]

The present invention has a light emitting element connected to a bias element, and a light receiving element that receives light from the light emitting element and outputs a current according to the amount of received light, and the light emitting element and the light receiving element are connected in series. At the same time, the amount of light emitted from the light emitting element is configured to change depending on the presence or absence of an object between the light emitting element and the light receiving element.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

Fig. 1 is a schematic implementation diagram of a mechanism for detecting the rotation speed of a motor to which an embodiment of the present invention is applied, Fig. 2 is a partially enlarged view of Fig. 1, and Fig. 3 is an optical detection circuit. Configuration diagram, 4th
The figure is an operation timing diagram of the circuit.

In FIG. 1, a disk 2 with a hole in one place is fixed to the rotating shaft of a motor 1 in order to detect the phase thereof. On the edge of this disk 2.

A detection unit 3 for optically detecting the position of the hole in the disk 2 is installed to sandwich the disk 2, and two signal lines, L, L, 0, come out from this optical detection unit 3.

FIG. 2 is a partially enlarged view of FIG. 1, and the optical object detection unit 3 is installed across the disk 2, and emits light whose amount changes depending on the supplied Turtle violet. The light from the element 4 reaches the light receiving element 5 only when the motor 1 rotates and the perforated part of the first disk 2 comes, and the light receiving element 5 outputs a current according to the amount of light received.

Furthermore, a bias element 6 is also mounted on the detection unit 3.

tI! FIG. 15 is a circuit configuration diagram according to one embodiment.

In this figure, the drive/detection circuit 9 is connected to the detection unit 3 through two signal lines L1 for supplying a power supply Vcc and a signal line L2 as an output line.

The signal line L1 is connected to the anode of the light emitting element 4 in the detection unit 3, and the cathode is connected to the a terminal of the bias element 6 and the collector of the light receiving element 5. The emitter of the light-receiving element 5 and the 6 terminals of the bias element 6 are connected together, and are connected to the drive/detection circuit 9 by a signal line L! is the load resistance 7 in the drive/detection circuit 9
is connected to the input of the Schmitt trigger element 8. Further, the terminal of the load resistor 7 is grounded. Here, the resistance value of the bias element 6 and the load resistance 7 are the same as those of the light emitting element 4. Assuming that the voltage drop of the light receiving element 5 is Vo Vp (at saturation), the following relationship exists between the LoW level input voltage limit value ■iL of the Schmitt trigger element B and the HiGH level input voltage limit value ViH. ing.

Resistance value of bias element 6 + load resistance 7 ViH< Vcc −(VD + VP) −・・−
......-(2) Next, based on the above configuration, motor 1
The operation of detecting the rotation speed will be explained.

When the part of the disk 2 without holes is located at the position of the detection unit 3, the light emitted from one light emitting element 4 is emitted.

This is because the light does not reach the light receiving element 5 as shown in FIG.

Output current Ip does not flow. In other words, the current ID flowing through the 0 light emitting element 4 is only the current IR flowing through the bias element 6, and the amount of light emitted by the 2 light emitting element 4 is small. Therefore, Schmi y))'J
The input voltage Vi of the resistor 8 is Lo from the above-mentioned formula (1).
W level, and the output voltage V of the Schmitt trigger element 8
o is Hi (3H level).

Next, when the part of the disk 2 with the hole comes to the position of the detection unit 3, the light from the light emitting element 4 reaches the light receiving element 5 I,
In this embodiment, since the light receiving element 5 is connected in series to the light emitting element 4, ID is as follows: ID=IR
+IC, the amount of light emission increases, and Ip further increases.

This feedback continues until saturation is achieved. At the time of saturation, the Schmitt trigger element 8
The output voltage VO of is at LoW level.

This relationship is shown in a time chart in FIG. 4, where the portions indicated by a, a', and a' are when the perforated portion of the disk 2 comes to the position of the detection unit 3. In FIG. 4, by measuring the period ll'' (time between a and 82) of the output of the Schmitt trigger element 6, the rotation speed of the motor 1 can be detected from its reciprocal.

According to a modification of this embodiment, the light emitting element 4 may be moved to the side of the signal line in FIG. 5. Also,
Regarding noise and voltage levels, the trigger element 8 may be used as a comparator element. In addition, although the light emitting element is caused to emit light by a bias element, this may be replaced by a method using weak external light.

〔Effect of the invention〕

According to the present invention, an amplifier circuit is not required in the drive/detection circuit, and at least two interface signal lines are required, so that one device can be made smaller and more functional. Furthermore, when there is an object between the light emitting element and the light receiving element, the current consumption can be extremely reduced, which is effective in reducing power consumption.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view in which an optical detection element is mounted to optically detect the rotation speed of the motor, Figure 2 is a side view showing a partially enlarged view of Figure 1, and Figure @3 is one implementation. FIG. 4 is a configuration diagram of an example optical detection circuit, and FIG. 4 is an operation timing diagram. 1...Motor, 2...Disk. 3...Detection unit y), 4...
・Light emitting element. K: Light receiving element, 6: Bias element. 7...Load resistance. 8...Schmitt trigger element. Katsuo Ogawa

Claims (1)

[Claims] A light-emitting element connected to a bias element; a light-receiving element that receives light from the light-emitting element and outputs a current according to the amount of light received; the light-receiving element is connected in series with the light-emitting element; 1. An optical detection circuit characterized in that the amount of light emitted by a light emitting element changes depending on the presence or absence of an object between the light emitting element and the light receiving element.