JP3152582B2 - Card detection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a card detection circuit for detecting the presence or absence or position of a card.

[0002]

BACKGROUND ART card detection circuit is used in various devices dealing with the card, the light-emitting element PD1 of a light emitting diode as shown in FIG. 6, the light receiving element PT1 and the resistor R _1, R ₂ consists of phototransistors It is configured. Light emitting diode PD1 and phototransistor PT
1 is a sensor element, and the light emitting diode PD1 is 5
V is connected between the DC power supply Vcc of V and the ground via a resistor R ₁ and irradiates light to the phototransistor PT 1 via the traveling path of the card C. The phototransistor PT1 is
5V DC power supply Vcc and connected sensor current Is flows through the resistor R ₂ between the ground point of the light emitting diode P
The light coming from D1 via the traveling path of the card C is received.

[0003] Images output terminal OUT1 from the connection point of the emitter and the resistor R ₂ of the transistor PT1 is derived and not block or blocks light from the light emitting diode PD1 card C is traveling along the traveling road to the phototransistor PT1 As a result, the signal voltage at the output terminal OUT1 becomes lower or higher. A circuit (not shown) detects the presence or absence or position of the card C by comparing the signal voltage of the output terminal OUT1 with a threshold. The resistance of the resistor R ₂ is manually adjusted by the measured value of the sensor current Is, that is, the sensor current Is is measured by a measuring instrument, and the measured value is replaced with one having an appropriate resistance, or the resistance R _{2 is changed.} Is used as the variable resistor, and its resistance value is the sensor current Is.
It is adjusted by the measured value of.

[0004]

In the above card detection circuit, the light emitting diode PD1 and the phototransistor PT
The variation of 1 (variation of sensitivity and light emission amount) is large,
This is about 40 times as wide as the sensor current Is, and the resistance R ₂ as a load of the phototransistor PT1 is
Needs to be adjusted. Adjustment of the resistor R _2, the sensor current Is measured by the measuring instrument and replace it with one having an appropriate resistance value by the measured value, or the resistance R ₂ as a variable resistor using the resistance value sensor current Is Since the adjustment is performed based on the measured values, manual manual operation is troublesome.

Here, the card C has a light transmittance of, for example, about 3%, and the light amount ratio (the ratio of the sensor current Is becomes the same) when the card blocks light and when it does not block light is:
Since it is only about 30 times, the variation of 40 times of the sensor current Is cannot be covered without adjusting the resistance.

Further, the sensor element Is composed of the light emitting diode PD1 and the phototransistor PT1 causes the sensor current Is to decrease during use due to dust on the card running path, performance deterioration, and the like. It cannot be known until it becomes impossible (the sensor current Is remains below the value corresponding to the threshold value). SUMMARY OF THE INVENTION It is an object of the present invention to provide a card detection circuit that can automatically adjust the load of a sensor element and can improve reliability and extend the life.

[0007]

In order to achieve the above object, the present invention is directed to a sensor element having a light emitting element and a light receiving element for detecting the presence or absence or position of a card, and the light receiving element of the sensor element. In series as load
A constant current circuit for changing the current of the sensor element according to the connected input signal, the optimal current of the sensor element from the output signal of the sensor element by changing the input signal of the constant current circuit determined on the Control means for setting an input signal of the constant current circuit to an input signal corresponding to the optimum current, and comparing the output signal of the sensor element with a threshold to detect the presence or absence or position of the card. is there.

According to a second aspect of the present invention, in the card detection circuit according to the first aspect, the control means changes an input signal of the constant current circuit to determine an optimum signal of the sensor element from an output signal of the sensor element. The current of the sensor element is obtained by repeatedly performing a sensor element current resetting operation of obtaining a current and setting an input signal of the constant current circuit to an input signal corresponding to the optimum current at a predetermined timing. Is reset according to the deterioration of.

According to a third aspect of the present invention, in the card detection circuit according to the first aspect, the control means is adapted to reduce deterioration of the sensor element by an optimum current of the sensor element obtained from an output signal of the sensor element. To correct the threshold value.

[0010]

According to the first aspect of the invention, the sensor element having the light emitting element and the light receiving element detects the presence or absence or the position of the card, and loads the light receiving element of the sensor element as a load.
A constant current circuit connected in series changes the current of the sensor element according to the input signal. The control means changes an input signal of the constant current circuit to obtain an optimum current of the sensor element from an output signal of the sensor element, sets an input signal of the constant current circuit to an input signal corresponding to the optimum current, and The presence / absence or position of the card is detected by comparing the output signal of the element with a threshold value.

According to a second aspect of the present invention, in the card detection circuit according to the first aspect, the control means obtains an optimum current of the sensor element from an output signal of the sensor element by changing an input signal of the constant current circuit. By repeating the sensor element current reset operation of setting the input signal of the constant current circuit to an input signal corresponding to the optimum current at a predetermined timing, the sensor element current is reset as the sensor element deteriorates I do.

According to a third aspect of the present invention, in the card detection circuit according to the first aspect, the control means includes an optimum current of the sensor element obtained from an output signal of the sensor element, and the threshold value is associated with the deterioration of the sensor element. Correct the value.

[0013]

FIG. 1 shows an embodiment of the present invention. This embodiment is an embodiment of the first and second aspects of the present invention, and includes a card detection unit 11 and a control unit 1 comprising a microprocessor.
2. It is composed of a D / A converter 13 and a voltage dividing circuit 14. The card detection unit 11 detects the presence or absence or position of a card at a predetermined position on a card travel path in various devices that handle cards. The card detection unit 11 includes a light emitting element PD2 composed of a light emitting diode, a light receiving element PT2 composed of a phototransistor, and a constant. It is constituted by a current circuit CI and current setting resistor R _3.

The light emitting diode PD2 and the phototransistor PT2 constitute a sensor element, and the light emitting diode P2
D2 irradiates light to the phototransistor PT2 through the travel path of which is connected via a resistor R ₃ to the card C between the DC power source Vcc and the ground point of 5V. Phototransistor P
T2 has a collector connected to the DC power supply Vcc of 5 V and an emitter connected to the ground via a constant current circuit CI as a load of the phototransistor PT2. The phototransistor PT2 receives light that arrives from the light emitting diode PD2 via the traveling path of the card C.

An output terminal OUT2 is derived from a connection point between the emitter of the phototransistor PT2 and the constant current circuit CI, and a constant sensor current Is flows through the phototransistor PT2 by the constant current circuit CI. The impedance of the phototransistor PT2 changes when the card C travels on the road and the input light from the light emitting diode PD2 is cut off or not cut off by the card C, and the signal voltage Vs of the output terminal OUT2 changes to the light emitting diode PD2.
It becomes lower or higher depending on the presence or absence of the card C between the phototransistor PT2 and the phototransistor PT2.

A control signal from the microprocessor 12 is converted into an analog signal by a D / A conversion circuit 13 so that
After the voltage is divided by 4, the voltage is input to the constant current circuit CI, and the constant current circuit CI changes the sensor current Is according to the input voltage Vi from the voltage divider 14. As shown in FIG. 2, when the constant current circuit current Ci changes from 0 to a larger value, the signal voltage Vs at the output terminal OUT2 changes from the voltage of the DC power supply Vcc to the voltage side of the ground point. Microprocessor 12
The A / D converter converts the signal voltage Vs of the output terminal OUT2 into a digital signal and monitors the signal, and compares the digital signal with a threshold value Vth to detect the presence or absence or position of the card C.

The voltage dividing circuit 14 includes resistors R ₄ and R ₅ , and outputs a control signal voltage from the D / A conversion circuit 13 to R ₄ / R ₅ .
The voltage is divided into (R ₄ + R ₅ ) and output to the constant current circuit CI.

The constant current circuit CI includes an operational amplifier IC1, a transistor Tr, and resistors R ₆ and R ₇ as shown in FIG. Sensor current Is flows through the transistor Tr and the current detection resistor R _6, together with the input signal voltage Vi from the voltage dividing circuit 14 is applied to the base of the transistor Tr through the operational amplifier IC1, a voltage of the current detection resistor R ₆ is operational is negatively fed back to the amplifier IC1 is the sensor current is is controlled to a value Vi / R ₆ corresponding to the input signal voltage from the voltage dividing circuit 14.

FIG. 4 shows an operation flow of this embodiment. When the power is turned on, the microprocessor 12
The control signal to the converter 13 is varied stepwise from the minimum value to the maximum value of the setting range to gradually change the input voltage Vi of the constant current circuit CI from the minimum value to the maximum value, thereby minimizing the sensor current Is. Value to maximum value, eg 0 to 3m
The output signal voltage Vs of the constant current circuit CI is monitored in a stepwise manner from A to 5 mA, and the sensor current Is when the Vs exceeds the threshold value Vth is measured as the sensor current value Is of the phototransistor PT2.

Here, the microprocessor 12 has a D /
Can be the control signal to A converter 13 knows the input voltage Vi of the constant current circuit CI, and, because it is Is = Vi / R _6, observed when the Vs exceeds the threshold value Vth D / A
From the control signal to the transducer 13 to know the input voltage Vi of the constant current circuit CI obtaining a sensor current Is of the phototransistor PT2 at Is = Vi / R ₆ becomes operational.

Next, the microprocessor 12 stores the measured sensor current Is in a non-volatile memory such as E ² P
The degree of deterioration of the sensor element is detected from the difference between the initial sensor current Is stored in the ROM in advance, and an alarm or the like that prompts maintenance is generated for deterioration exceeding a specified value. According to the deterioration degree of the sensor element, the set current value of the constant current circuit is set to an optimum value corresponding to the deterioration degree of the sensor element. For example, if the purpose is to detect the presence or absence of a card, the light amount without the card (the sensor current Is of the phototransistor PT2). If it is set to 100%, the worst amount of light decreases to about 5% (1/20 of that without the card) when the card is present, so the set current value of the constant current circuit is set to 1 for the measured sensor current Is of the phototransistor PT2. / 1
By setting it to 0, the output voltage Vs of the sensor circuit is sufficiently on the Vcc side when there is no card, and is sufficiently GN when there is a card.
D side.

Thereafter, the microprocessor 12
By monitoring the output signal voltage Vs of the constant current circuit CI and comparing Vs with the threshold value Vth, the light emitting diode PD2
The operation for detecting the presence or absence or position of the card C between the phototransistor and the phototransistor PT2 and detecting the presence or absence or position of the card C is repeated until the power is turned off.

As described above, this embodiment is an embodiment of the first aspect of the present invention, in which the light-emitting element PD2 composed of a light-emitting diode for detecting the presence or absence or position of the card C and the light-receiving element composed of the phototransistor PT2 are used. A constant current circuit CI connected as a load to the sensor element to change the current Is of the sensor element in accordance with the input signal Vi; and changing the input signal Vi of the constant current circuit CI to output the sensor element The optimum current of the sensor element is obtained from the signal Vs, the input signal of the constant current circuit CI is set to an input signal corresponding to the optimum current, and the output signal of the sensor element is compared with a threshold to determine whether the card C is present. Alternatively, the microprocessor 12 as the control means for detecting the position is provided, so that the load of the sensor element can be automatically adjusted. Can, it is possible to greatly improve the reliability.

This embodiment is an embodiment of the invention according to the second aspect. In the card detection circuit according to the first aspect, the control means 12 changes the input signal of the constant current circuit CI to provide a sensor. The sensor element current reset operation of finding the optimum current of the sensor element from the output signal of the element and setting the input signal of the constant current circuit CI to an input signal corresponding to the optimum current is repeated every time the power is turned on. As a result, the current of the sensor element is reset according to the deterioration of the sensor element, so that the service life can be extended and the deterioration degree of the sensor can be compared with the initial sensor current stored in the nonvolatile memory in advance. To know the maintenance time. The microprocessor 1
2 is to change the input signal of the constant current circuit CI to obtain the optimum current of the sensor element from the output signal of the sensor element,
The sensor element current reset operation of setting the input signal of the constant current circuit CI to an input signal corresponding to the optimum current was repeated every time the power was turned on. The current of the sensor element may be reset according to the deterioration of the sensor element by repeatedly performing the predetermined timing other than the above.

In one embodiment of the present invention, in the above embodiment, the microprocessor 12 is
The current Is of the sensor element according to the degree of deterioration of the sensor element
Instead of resetting, the threshold value Vth is corrected in accordance with the degree of deterioration of the sensor element. Note that, instead of correcting the threshold value Vth according to the degree of deterioration of the sensor element every time the power is turned on, the microprocessor 12 repeats the processing at a predetermined timing other than when the power is turned on. The threshold value Vth may be corrected. In the embodiment of the invention according to the third aspect of the present invention, in the card detection circuit according to the first aspect, the control unit 12 is configured to perform the above-described operation according to the deterioration of the sensor element by the optimum current of the sensor element obtained from the output signal of the sensor element. Since the threshold value is corrected, the life can be extended.

FIG. 5 shows another embodiment of the present invention. This embodiment is different from the above embodiment in that the constant current circuit CI is provided on the DC power supply Vcc side, and two resistors R ₃₁ and R ₃₂ are provided as the current setting resistor R _{3 and} are switched and used by the switch SW. The sensor current I
The measurement range of s can be expanded. In the above embodiment, the D / A converter 13 is connected to the microprocessor 12
A PWM circuit for converting a control signal such as a PWM (pulse width modulation) signal, a frequency signal or the like into a voltage signal suitable for an input signal of the voltage dividing circuit 14, a frequency / voltage conversion circuit, or the like may be used. Further, the microprocessor 12 may display the deterioration of the sensor element detected as described above on the display unit.

[0027]

As described above, according to the first aspect of the present invention, a sensor element having a light emitting element and a light receiving element for detecting the presence or absence or position of a card, and connected to the sensor element as a load and responding to an input signal. A constant current circuit that changes the current of the sensor element, and obtains an optimum current of the sensor element from an output signal of the sensor element by changing an input signal of the constant current circuit. Set the input signal according to the optimal current,
Since control means for detecting the presence or absence or position of the card by comparing the output signal of the sensor element with a threshold value is provided, the load adjustment of the sensor element can be automatically performed, and the reliability is greatly improved. Can be done.

According to a second aspect of the present invention, in the card detecting circuit according to the first aspect, the control means changes an input signal of the constant current circuit to output a signal of the sensor element from the output signal of the sensor element. The current of the sensor element is obtained by repeatedly performing a sensor element current resetting operation of obtaining an optimum current and setting an input signal of the constant current circuit to an input signal corresponding to the optimum current at a predetermined timing. Since the resetting is performed in accordance with the deterioration of the sensor element, the service life can be extended.

According to a third aspect of the present invention, in the card detection circuit according to the first aspect, the control means deteriorates the sensor element by an optimum current of the sensor element obtained from an output signal of the sensor element. Accordingly, the threshold value is corrected, so that the service life can be extended.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram illustrating a relationship between an input current of a constant current circuit and an output signal voltage of a card detection unit according to the embodiment.

FIG. 3 is a circuit diagram showing a part of the embodiment.

FIG. 4 is a flowchart showing an operation flow of the embodiment.

FIG. 5 is a circuit diagram showing a part of another embodiment of the present invention.

FIG. 6 is a circuit diagram showing a conventional card detection circuit.

[Explanation of symbols]

 PD2 Light emitting diode PT2 Phototransistor CI Constant current circuit 11 Card detector 12 Microprocessor 13 D / A converter 14 Voltage divider circuit

Claims (3)

(57) [Claims] 1. A sensor element having a light-emitting element and a light-receiving element for detecting the presence / absence or position of a card, and a current connected to the light-receiving element of the sensor element which is connected in series as a load to change the current of the sensor element according to an input signal. A constant current circuit for changing the input signal of the constant current circuit to obtain an optimum current of the sensor element from an output signal of the sensor element, and inputting the input signal of the constant current circuit according to the optimum current. A card detection circuit for setting a signal and comparing the output signal of the sensor element with a threshold to detect the presence or absence or position of the card. 2. The card detection circuit according to claim 1, wherein
The control means changes an input signal of the constant current circuit to obtain an optimum current of the sensor element from an output signal of the sensor element, and converts an input signal of the constant current circuit to an input signal corresponding to the optimum current. A card detection circuit, wherein the current of the sensor element is reset with the deterioration of the sensor element by repeatedly performing a sensor element current reset operation of setting the sensor element at a predetermined timing. 3. The card detection circuit according to claim 1, wherein
A card detection circuit, wherein the control means corrects the threshold value in accordance with deterioration of the sensor element by an optimum current of the sensor element obtained from an output signal of the sensor element.