JPH07288459A - Sensor device using photocoupler - Google Patents

Abstract

PURPOSE:To correct the quantity of light emitted from a light emitting element in a simple circuit constitution. CONSTITUTION:A microcomputer 15 performs the ON control of a switch SW1 when a power supply is turned on. Thus the DC voltage Vcc1 and a current set by a current control circuit 20 flow to an LED 13. At the same time, a current flows to a phototransistor 14 in response to the quantity of light received from the LED 13. Then the voltage V1 set by the current to the phototransistor 14 is fly backed to the control voltage input terminal of the current control circuit 20. Thus the circuit 20 stores the data on the voltage V1 and sets a resistance level to keep a proper quantity of light emitted from the LED 13 based on the stored data. Thus the current flowing to the LED 13 is controlled. As a result, the quantity of light emitted from the LED 13 can be corrected in a simple circuit constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sensor device using a photo coupler used in a hard copy device for making a hard copy on a recording sheet, and particularly to a sensor device using a photo coupler capable of preventing erroneous detection. Regarding

[0002]

2. Description of the Related Art In recent years, hard copy devices for making hard copies of various images and data on recording paper have become popular not only for business use but also for general households. Such a hard copy device is provided with a sensor device using a photocoupler for detecting the position of the recording paper or the ink sheet.

FIG. 2 is a circuit diagram showing a sensor device using such a conventional photocoupler.

In FIG. 2, reference numerals 51 and 52 are input terminals to which a constant DC voltage Vcc2 for power supply is introduced. The input terminal 51 is connected to the reference potential point through a series connection of the resistor R51 and the anode / cathode path of the light emitting diode 53.

The input terminal 52 is connected to a reference potential point via a series connection of a resistor R52 and an anode / cathode path of a phototransistor 54.

The light emitting diode 53 and the phototransistor 54 are arranged on one surface side and the other surface side of the path through which the recording paper is conveyed.

The connection point A2 between the resistor R52 and the phototransistor 54 is connected to the input port of the microcomputer 55, and the voltage V2 at this connection point A2 is introduced to the input port of the microcomputer 55. The microcomputer 55 detects whether or not the voltage V2 introduced to the input port is equal to or higher than the threshold level, and based on this, the recording paper has the light emitting diode 5
3 and the phototransistor 54, it is determined whether or not the recording sheet is conveyed and the printing operation is controlled based on this determination.

In a sensor device using such a conventional photocoupler, a DC voltage V is applied to the light emitting diode 53.
A current set by cc2 and the resistor R51 flows, whereby the light emitting diode 53 emits light. A current flows through the phototransistor 54 according to the amount of light received from the light emitting diode 53. The voltage V2 at the input port of the microcomputer 55 changes depending on the current flowing through the resistor R52 and the phototransistor 54.

When there is no obstruction between the light emitting diode 53 and the phototransistor 54, that is, when the recording paper does not pass between the light emitting diode 53 and the phototransistor 54, the light from the light emitting diode 53 is the phototransistor. The phototransistor 54 receives the light.
Turns on. When there is an obstacle between the light emitting diode 53 and the phototransistor 54, that is, when the recording paper passes between the light emitting diode 53 and the phototransistor 54, the light from the light emitting diode 53 is received by the phototransistor 54. Then, the phototransistor 54 is turned off.

The voltage V2 applied to the input port of the microcomputer 55 becomes the voltage at the reference potential point when the phototransistor 54 is on, and the phototransistor 54
When is off, the voltage is the DC voltage Vcc2. When the voltage V2 becomes the voltage at the reference potential point, the microcomputer 55 determines that the voltage V2 is lower than the threshold level, and determines that the recording paper has not passed between the light emitting diode 53 and the phototransistor 54. . Also,
In the microcomputer 55, the voltage V2 is DC voltage Vcc
When it becomes 2, it is determined that the voltage V2 is equal to or higher than the threshold level, and it is determined that the recording paper passes between the light emitting diode 53 and the phototransistor 54.

As described above, according to the sensor device using such a conventional photocoupler, the microcomputer 55 can determine the passage of the recording paper between the light emitting diode 53 and the phototransistor 54.

The sensitivity of the phototransistor 54 is set based on the amount of light emitted from the light emitting diode 53. The setting in this case is such that the light emission amount of the light emitting diode 53 is reduced by 50% in five years due to the secular change. Therefore, in consideration of the decrease in the light amount, the resistance R51 of the resistor R51 is adjusted so that a larger current flows through the light emitting diode 54. The resistance value was set. Therefore, when the recording paper is thin or semi-transparent, there is a high probability of malfunction.

[0013]

In the conventional sensor device using the photocoupler, a large amount of current is made to flow through the light emitting element in consideration of the secular change of the light emitting amount of the light emitting element. Therefore, when the recording paper is thin or semi-transparent, there is a high probability of malfunction.

Therefore, an object of the present invention is to provide a sensor device using a photocoupler capable of correcting the light emission amount of a light emitting element with a simple circuit configuration.

[0015]

According to a first aspect of the present invention, there is provided a sensor device using a photocoupler according to the present invention. The light emitting element emits light when a current flows, and the light receiving element receives light from the light emitting element. A resistor connected in series to the light receiving element, a DC voltage applying means for applying a constant DC voltage to the resistor and the light receiving element connected in series, and a voltage at a connection point between the resistor and the light receiving element. The light emitting element and the light receiving element are detected by detecting the voltage at the connection point between the resistor and the light receiving element, and the current control circuit for controlling the current flowing through the light emitting element based on the stored detection result. A microcomputer that determines whether or not there is something that blocks light, and if there is something that blocks light between the light emitting element and the light receiving element, the detection of the voltage of the current control circuit is turned off. To the state Characterized by comprising a that switch circuit.

[0016]

With this structure, the current control circuit detects and stores the voltage at the connection point between the resistor and the light receiving element when there is no light blocking element between the light emitting element and the light receiving element. Then
Since the current flowing through the light emitting element is controlled based on the stored detection result, the light emission amount of the light emitting element can be corrected with a simple circuit configuration.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of a sensor device using a photocoupler according to the present invention.

In FIG. 1, reference numerals 11 and 12 are input terminals to which a constant DC voltage Vcc1 for power supply is introduced. The input terminal 11 is connected to the reference potential point through a series connection of the current control circuit 20 and the anode / cathode path of the light emitting diode 53. The input terminal 12 is connected to the reference potential point via a series connection of the resistor R12 and the anode / cathode path of the phototransistor 14.

The light emitting diode 13 and the phototransistor 14 constitute a photocoupler, and are arranged on one surface side and the other surface side of the path through which the recording paper is conveyed.

The connection point A1 between the resistor R12 and the phototransistor 14 is connected to the input port of the microcomputer 15 and also to one end of the switch SW1. As a result, the voltage V1 at the connection point A1 is introduced to the input port of the microcomputer 15 and one end of the switch SW1. The other end of the switch SW1 is connected to the control voltage input terminal of the current control circuit 20. Current control circuit 20
Is reset once the voltage guided to the control voltage input terminal exceeds a predetermined level and erases the previously stored data, and then stores the data of the voltage guided to the control voltage input terminal. The resistance value is adjusted based on the obtained data to control the current flowing through the light emitting diode 13. Here, the current control circuit 20 sets the resistance value in the reset state to a higher value so that the voltage V1 when the power is turned on varies depending on the secular change of the light emitting diode 13.

The microcomputer 15 creates a switch control signal a1 for turning on the switch SW1 when the power is turned on and supplies it to the control signal input terminal of the switch SW1.
Further, the microcomputer 15 determines whether the recording paper passes between the light emitting diode 13 and the phototransistor 14 by detecting whether the voltage V1 introduced to the input port is equal to or higher than the threshold level, Based on such a determination, the recording paper is conveyed and the printing operation is controlled.

The operation of such an embodiment will be described below.

First, the microcomputer 15 creates a switch control signal a1 for turning on the switch SW1 when the power is turned on and supplies it to the control signal input terminal of the switch SW1. As a result, the switch SW1 is turned on.

In this state, the DC voltage Vcc1 and the current set by the current control circuit 20 flow through the light emitting diode 13, and the current flows through the phototransistor 14 according to the amount of light received from the light emitting diode 13. , Resistor R12 and phototransistor 14 set by this current
The voltage V1 at the connection point A1 with is flybacked to the control voltage input terminal of the current control circuit 20. Thereby, the current control circuit 20 stores the data of the voltage V1, sets the resistance value such that the light emission amount of the light emitting diode 13 becomes an appropriate level by the stored data, and controls the current flowing through the light emitting diode 13. To do. Thereby, the light emitting diode 1
3 emits light at an appropriate level with respect to the sensitivity of the phototransistor 14.

After that, when the recording paper does not pass between the light emitting diode 13 and the phototransistor 14,
The light from the light emitting diode 13 is the phototransistor 14.
When the phototransistor 14 is turned on and the recording paper passes between the light emitting diode 13 and the phototransistor 14, the light emitting diode 13 is received.
The light from is not received by the phototransistor 14, and the phototransistor 14 is turned off.

A voltage at the reference potential point is applied to the input port of the microcomputer 15 when the phototransistor 14 is on, and a voltage Vcc1 is applied when the phototransistor 14 is off. When the voltage at the reference potential point is applied to the input port, the microcomputer 15 outputs the voltage V
1 is lower than the threshold level, it is determined that the recording paper does not pass between the light emitting diode 13 and the phototransistor 14, and when the voltage Vcc1 is applied to the input port, the voltage V1 becomes the threshold. It is detected that the recording paper is above the level, it is determined that the recording paper passes between the light emitting diode 13 and the phototransistor 14, and the conveyance of the recording paper and the control of the printing operation are performed based on such a judgment. ing.

According to such an embodiment, the current control circuit 20 stores the data of the voltage V1 when the power is turned on, and thereafter, the resistance so that the light emission amount of the light emitting diode 13 becomes an appropriate level by the stored data. Since a value is set to control the current flowing through the light emitting diode 13, the light emitting diode 13 can emit light at an appropriate level with respect to the sensitivity of the phototransistor 14, and when the recording paper is thin or translucent. In such cases, the probability of malfunction can be reduced.

In the embodiment of FIG. 1, the microcomputer 15 controls the switch SW1 to be turned on when the power is turned on so that the data of the voltage V1 is stored in the current control circuit 20, but the recording paper is the light emitting diode 13. The switch S while passing between the phototransistors 14
W1 is turned off, and switch S is turned off in other states.
W1 may be controlled to be turned on. Further, in the embodiment of FIG. 1, a light emitting diode is used as the light emitting element,
Other light emitting elements, such as small light bulbs, may be used. Further, although the phototransistor is used as the light receiving element in the embodiment of FIG. 1, another light receiving element, for example, a photodiode may be used.

[0030]

As described above, according to the present invention, since the light emission amount of the light emitting element can be corrected with a simple circuit configuration, the probability of causing a malfunction when the recording paper is thin or semi-transparent, etc. It can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a sensor device using a photocoupler according to the present invention.

FIG. 2 is a circuit diagram showing a sensor device using a conventional photocoupler.

[Explanation of symbols]

 13 light emitting diode 14 phototransistor 15 microcomputer 20 current control circuit R12 resistance SW1 switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41J 29/00 G01D 5/36 U

Claims (1)

[Claims] 1. A light emitting element that emits light when a current flows, a light receiving element that receives light from the light emitting element, a resistor connected in series to the light receiving element, the resistor and the light receiving element. DC voltage applying means for applying a constant DC voltage to the series connection of the, and the voltage at the connection point between the resistor and the light receiving element is detected and stored, and the current flowing through the light emitting element is controlled based on the stored detection result. A current control circuit, and a microcomputer that determines whether or not there is something that blocks light between the light emitting element and the light receiving element by detecting the voltage at the connection point between the resistor and the light receiving element, A sensor device using a photocoupler, comprising: a switch circuit for turning off the detection of the voltage of the current control circuit when there is a light blocking element between the light emitting element and the light receiving element. Place