JP3033740B2 - Photosensor position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the position of an object using a photo sensor.

[0002]

2. Description of the Related Art When a position of an object to be moved or carried is detected at a plurality of positions by a plurality of photo sensors, conventionally,
In order to process the output from the photo sensor by a processing device such as a CPU, an input interface circuit is required for each photo sensor. FIG. 4 shows such a conventional example.

[0003] In FIG. 4, photointerrupters P1 to P3, which are photosensors combining a light emitting diode D and a phototransistor T, are connected to respective input / output terminals of a connector CN.
A voltage (for example, 5 V) from the power supply E is separately applied to P3. At the output terminals of the photointerrupters P1 to P3,
Input interface circuits IF1 to IF3 for each are connected via a connector CN, and outputs from the respective photointerrupters P1 to P3 are input to a processing device such as a CPU via the respective input interface circuits IF1 to IF3.

[0004]

However, in such a circuit configuration in which the input interface circuits IF1 to IF3 are provided for each of the photointerrupters P1 to P3, the number of input interface circuits increases in proportion to the photosensor usage amount. There is a problem that the occupation ratio of the internal wiring is increased and the substrate needs to be enlarged, and a problem that the number of wirings between the substrate and the photosensor increases.

An object of the present invention is to integrate the input interface circuits conventionally required by the number of photosensors into one input interface circuit, to simplify the circuit, and to reduce the number of pins and wiring of the connector. It is an object of the present invention to provide a position detecting device whose number can be significantly reduced.

[0006]

According to the present invention, a plurality of photosensors are connected in series, one end of the series circuit is connected to a power source, and the other end is connected to a processing device such as a CPU.
A plurality of input interface circuits are connected, and a voltage drop resistor having a different resistance value is connected in parallel to each photosensor.

When a photointerrupter combining a light emitting diode and a phototransistor is used as a photosensor, a voltage drop resistor having a different resistance value is connected in parallel to each phototransistor. The input interface circuit preferably includes an A / D converter.

[0008]

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In this embodiment, three photosensors P1 to P3 are connected in series, one end of the series circuit is connected to a power source E by input terminals IN1 and IN2 of a connector CN, and the other end of the series circuit is The output terminals OU1 and OU2 of the connector CN are connected to one input interface circuit IF. The input interface circuit IF includes an A / D converter I
C and a current detection resistor R4.

In this embodiment, as each of the photosensors P1 to P3, a reflection type photointerrupter in which a light emitting diode D and a phototransistor T are combined is used. In each of the photosensors P1 to P3, an output from the light emitting diode D is output. When the reflected light enters the phototransistor T after being reflected by an object (for example, a sheet of paper to be conveyed) TH, the phototransistor T is turned on. To the phototransistors T of the photosensors P1 to P3, voltage drop resistors R1 to R3 having different resistance values are connected in parallel.

Next, the operation of this embodiment will be described.
Before the photosensors P1 to P3 detect the form, the voltage from the point a to the point b is reduced because the phototransistors T of the photosensors P1 to P3 are OFF.
It decreases by the voltage drop due to the sum of R3 (R1 + R2 + R3).

One of the photo sensors P1 to P3,
Alternatively, when all the documents are detected, the corresponding phototransistor T is turned on. At this time, the voltage from the point a to the point b increases by the voltage drop due to the voltage drop resistor connected in parallel to the phototransistor T which is turned ON.
As an example, when the photosensor P1 is turned on, the resistance between the points D and E is a parallel connection of the resistance of the phototransistor T of the photosensor P1 and the voltage dropping resistor R1. (The resistance of the phototransistor T of the photosensor P1) / R1 + (the resistance of the phototransistor T of the photosensor P1).

Here, assuming that the ON resistance of the phototransistor T of the photosensor P1 is negligibly small compared to the resistance R1, the resistance value in the above equation can be regarded as substantially zero, and the points D to E The voltage drop between them is almost zero. Therefore, the voltage between the point A and the point B increases by the voltage drop in the voltage drop resistor R1.

The current value (the voltage value appearing at the point c by the current detecting resistor R4) changed by the increase / decrease of the voltage between the point a and the point b is converted by the A / D converter IC from the analog data into the digital data. And sends it to a processing device such as a CPU.

Here, by setting the constants of the voltage drop resistors R1 to R3 to R1 = 100Ω, R2 = 200Ω, and R3 = 400Ω, as shown in FIG. Since the value does not reach the value, the phototransistors of any of the photosensors P1 to P3 are ON
Can be identified.

Therefore, by processing the data sent by a processing device such as a CPU, the photo sensors P1 to P
It is possible to identify which of the photo sensors 3 has detected the form.

In the above embodiment, the case where the number of photosensors is three has been described, but the number of photosensors connected is A / D.
.., N can be increased depending on the capacity of the converter.

Further, in the above embodiment, the resistance values of the voltage drop resistors are set to 100Ω, 200Ω, and 400Ω. However, if the combined resistance value does not become the same value as another combination (for example, 100 × 2n-1Ω (n =
1, 2, 3,..., N)), the cost can be reduced by using an inexpensive one.

Further, in the above-described embodiment, a configuration using a reflection type photo interrupter is used, but a transmission type photo interrupter may be used.

[0020]

As described above, according to the present invention, the input interface circuits conventionally required by the number of photosensors to be used can be integrated into one input interface circuit, and the circuit can be simplified. it can. Also,
Conventionally, the number of wires is 3 × N for power supply, ground, and signal lines.
Although only (the number of photosensors to be used) is required, according to the present invention, the number of photosensors is four regardless of the number of photosensors used, and the number of pins and wires of the connector can be greatly reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating an example of detection by a photo sensor.

FIG. 3 is a diagram illustrating a relationship between ON / OFF of a photosensor and a resistance value.

FIG. 4 is a circuit diagram of a conventional example.

[Explanation of symbols]

 P1 to P3 Photosensor D Light emitting diode T Phototransistor R1 to R3 Voltage drop resistor R4 Current detection resistor IF Input interface circuit IC A / D converter CN connector IN1, IN2 input terminal OU1, OU2 output terminal

Continuation of the front page (72) Inventor Toshiyuki Araya 5-7-1 Shiba, Minato-ku, Tokyo NEC Corporation (56) References JP-A-5-34111 (JP, A) JP-A-1-168805 (Japanese) JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 102 G01D 5/26-5/38

Claims (3)

(57) [Claims] A plurality of photosensors are connected in series, one end of the series circuit is connected to a power supply, and the other end is connected to a CP.
A position detecting device using a photosensor, wherein the photodetector is connected to one input interface circuit for a processing device such as U, and a voltage drop resistor having a different resistance value is connected in parallel to each photosensor. 2. Each of the photosensors is a photointerrupter in which a light emitting diode and a phototransistor are combined, and each phototransistor is connected in parallel with a voltage drop resistor having a different resistance value.
A position detection device using the photosensor described in the above. 3. The position detecting device according to claim 1, wherein the input interface circuit includes an A / D converter.