JPH0311578B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to power saving of a photoelectric detection sensor that detects mechanical displacement and converts it into an electrical quantity.

In measuring instruments, machine tools, etc., mechanical linear displacement,
Alternatively, photoelectric detection sensors are often used to detect rotational displacement.

Figure 1 shows a principle diagram of a conventionally used photoelectric detection sensor, in which 1 is a light emitting diode for a light source, 2 is a resistor that determines the current flowing through the light emitting diode 1, and 3 is a phototransistor for light reception. , 4 is a resistor that determines the current of the phototransistor 3, and 5 is a grid provided between the light emitting diode 1 and the phototransistor 3 and provided with a slit 5a for opening and closing the optical path.

The photoelectric detection sensor having the configuration shown in FIG. 1 opens and closes the optical path emitted from the light emitting diode 1 by transmitting mechanical displacement of a measuring instrument or a machine tool (not shown) to the grating 5. , the photocurrent of the phototransistor 3 is changed in response to the mechanical displacement of the grating 5, and an output voltage obtained by converting the mechanical displacement into an electrical quantity is detected from both ends of the resistor 4.

However, such a photoelectric detection sensor has the disadvantage that a light source must be turned on at all times in order to detect mechanical displacement, resulting in high power consumption. In particular, when such a photoelectric detection sensor is employed in a battery-powered measuring instrument, the disadvantage of high power consumption becomes a major problem.

The present invention has been made in order to eliminate such drawbacks and provide a photoelectric detection sensor with reduced power consumption.

Hereinafter, one embodiment of the present invention will be described with reference to the configuration diagram shown in FIG.
This will be explained based on the waveform diagram shown in FIG.

In FIG. 2, numerals 1 to 5 indicate the same components as explained in FIG.

6 is an oscillation circuit for blinking the light emitting diode 1; 7 is a transistor switch; 8 is a resistor for determining the drive current of the transistor switch 7; and 9 is a retriggerable monostable multivibrator. Here, the oscillation circuit 6 is preferably a rectangular wave oscillator with an oscillation frequency of several KHz, for example
Consists of TTL gates. Further, the retriggerable monostable multivibrator 9 generates a pulse for a fixed period of time every time a trigger signal is input.

In this configuration diagram, it is assumed that the optical path between the light emitting diode 1 and the phototransistor 3 is opened and closed as shown in FIG. 3a due to mechanical displacement of the grating 5. However, in the figure, the H level indicates that the optical path is open, and the L level indicates that the optical path is closed.

On the other hand, since the transistor switch 7 is turned on and off by the output of the oscillation circuit 6, the light emitting diode 1 blinks at a period T as shown in FIG. 3b. Therefore, at this time, light as shown in FIG. 3c reaches the phototransistor 3 and is inputted to the monostable multivibrator 9 as an electric signal. Retriggerable monostable multivibrator 9
operates at the rising edge of this electrical signal and converts it into a pulse width t that is longer than the blinking period T of the light emitting diode 1 and does not exceed twice this blinking period T, as shown in FIG. 3d. Therefore, when the received light signals are continuous as shown in FIG. 3C, the retriggerable monostable multivibrator 9 eventually becomes
As shown in Figure e, a signal approximately corresponding to the period in which the optical path is opened and closed is output.

That is, by blinking the light emitting diode 1 in a time sufficiently shorter than the mechanical displacement of the grating 5, the output will be as shown in FIG.
A signal similar to can be obtained.

Since the light emitting diode 1 blinks at the period T, the average power consumption is naturally smaller than when it is constantly lit. The degree of improvement is determined by the ratio of the lighting time to the non-lighting time, and is greater as the lighting time is made shorter than the non-lighting time. for example,
If the lighting time of the light emitting diode 1 is 30 μS and the non-lighting time is 170 μS, the average power consumption can be reduced to 1/7.

As explained above, in the photoelectric detection sensor of the present invention, a grating having slits is provided between a light source and a light receiving circuit, and a light emitting diode serving as a light source is moved at a period sufficiently shorter than the period at which the optical path is opened and closed by the grating. and a retriggerable monostable multivibrator that is triggered by the output signal of the light receiving circuit and outputs a pulse signal with a time width longer than the blinking cycle of the light source and shorter than twice the cycle. Because of this feature, the power consumption of the light source during detection operations can be significantly reduced, which has the effect of making the device more compact, especially when applied to battery-powered measuring devices. be.

[Brief explanation of the drawing]

FIG. 1 is a principle diagram of a conventional photoelectric detection sensor, FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 3 is an explanatory diagram of the operation of the embodiment shown in FIG. In the figure, 1 is a light emitting diode, 3 is a phototransistor, 5 is a grid, 6 is an oscillation circuit, 9 is a monostable multivibrator, and 11 is an integrating capacitor.

Claims (1)

[Scope of Claims] 1. A photoelectric detection sensor provided with a grating that opens and closes an optical path between a light source and a light receiving circuit of the light source, comprising: a period in which the grating opens and closes an optical path between the light source and the light receiving circuit; A drive circuit that blinks the light source at a sufficiently shorter cycle, and a light receiving circuit that is triggered by an output signal of the light receiving circuit, and which is longer than the blinking cycle of the light source and does not exceed twice the blinking cycle with one trigger. A photoelectric detection sensor comprising a retriggerable monostable multivibrator that outputs a pulse with a time width.