JP4842573B2 - Sensor detection circuit and device provided with the detection circuit - Google Patents

Description

  The present invention relates to a sensor detection circuit and an apparatus provided with an open detection circuit, and more particularly, to a recording apparatus that performs control by mounting a plurality of optical sensors in a printer that performs printing with a recording head on a recording medium. The present invention relates to a sensor detection circuit.

  In recent years, with the spread of personal computers and digital cameras, printers that record information such as desired characters and images on a sheet-like recording medium such as paper or film are widely used as output devices.

  A printer generally has a configuration in which printing is performed with a recording head on a recording medium such as plain paper or dedicated paper, and a plurality of optical sensors are mounted for various purposes. Specifically, the presence / absence of a recording medium at the paper feeding and discharging positions, detection of the leading edge of the recording medium being conveyed, detection of the position of the recording head, detection of the presence / absence of an ink cartridge, jam opening, etc. And detection of the state of a mechanism that operates the recording medium and the recording head.

  In general, an optical sensor includes a photodiode and a phototransistor, and detects the presence or absence of an object to be confirmed based on whether the phototransistor has received light emitted from the photodiode. Broadly speaking, there are two types: a transmissive sensor arranged so that the photodiode and the phototransistor face each other, and a reflective sensor arranged in the same direction. In order to electrically drive such an optical sensor, three lines of a power supply line (VCC), a GND line, and an output line are required.

  In general, in a printer, the optical sensor is not mounted on a control board on which a CPU or the like is mounted. For each purpose such as detection of the presence / absence of a cartridge, detection of door opening / closing in jam processing, detection of a mechanism for operating a recording medium or a recording head, etc., they are mounted on individual substrates at corresponding detection positions.

  FIG. 4 is a diagram illustrating an example of connection between a control board and an optical sensor board in a general printer. As shown in the drawing, each of the photosensor boards PI1 to PI12 has a control board 1 on which a CPU 10 for controlling the printer is mounted, and a wiring composed of a power supply line (VCC), a GND line, and an output line. Connected with.

  As the number of photosensors increases, wiring consisting of a set of three connecting the control board and the photosensor board becomes a troublesome problem in printers that are becoming smaller. For example, in the example of FIG. 4, 3 × 12 = 36 wires are required.

  In order to reduce the number of signal lines required for connection between the control board and the plurality of photosensor boards, several methods have been proposed. As shown in FIG. 5, the first method is a method of selecting an optical sensor to be read by a sensor selection signal output from a plurality of ports of the CPU 10 of the control board 1. As shown in FIG. 6, the second method is a method in which the control circuit 6 for serial interface is mounted on each optical sensor board, and the optical sensor to be read is selected from the CPU 10 of the control board 1.

  However, since the conventional method is cascade-connected from the control substrate to the first photosensor substrate and from the first photosensor substrate to the second photosensor substrate, it is desirable to further reduce the number of wirings between the substrates. Has been.

  For example, in the method of FIG. 5, in addition to three power lines, GND lines, and output lines, up to four optical sensors, the number of selector ports is two, a total of five wires, and eight optical sensors. Until then, the number of selector ports is three and a total of six wires are required. As the number of optical sensors increases, the number of wires between the substrates increases. The method of FIG. 6 requires a total of six power lines, one GND line, three serial control lines for SCLK, TX, RX, and one output line.

  In any of the methods, when cascade connection is established, in the intermediate substrate such as the first optical sensor substrate 2, in addition to the wiring with the control substrate 1 (wiring between the connectors 11-21), the second optical sensor substrate is connected. Wiring (wiring between the connectors 22-31) is required. For this reason, when downsizing the apparatus, it is necessary to further reduce the number of wirings between the substrates.

  Such a problem is not limited to a printer, but is a problem common to various devices and electronic devices using a plurality of optical sensors. Further, the type of sensor is not limited to the optical sensor.

  The present invention has been made in view of the above situation, and an object of the present invention is to reduce the number of signal lines connecting between substrates in a configuration in which a plurality of sensor substrates are cascade-connected from a control substrate.

A sensor detection circuit as an aspect of the present invention that achieves the above object includes a plurality of sensor substrates each mounted with a sensor,
A control circuit that includes a control unit that outputs a selection signal for selecting any one of the sensors and receives an output signal from the sensor, and that supplies power to the plurality of sensor substrates. There,
In the control board and the plurality of sensor boards, power supply wiring, the selection signal, and the output signal are cascade-connected,
Each sensor board
Voltage range determining means for determining whether or not the voltage of the selection signal is within a predetermined range;
When the voltage range determination means determines that the voltage of the selection signal is within the predetermined range, the output range switching means for outputting the output of the sensor mounted on the substrate as the output signal ,
Each of the predetermined ranges corresponding to each of the plurality of sensor boards is set so as not to overlap with each other, and has a substantially equal size, and is set at a predetermined interval between the voltage value of the power source and GND. Yes,
It is characterized by that.

  The predetermined ranges of the sensor boards should not overlap each other, and the predetermined ranges of the plurality of sensor boards are substantially equal in size and are set at a predetermined interval between the voltage value of the power supply and GND. It may be.

  As the sensor, for example, an optical sensor that outputs a signal corresponding to one of the two values is suitable.

  As a specific configuration of the voltage range determination means, there is a configuration including two comparators corresponding to an upper limit and a lower limit of a predetermined range.

  As the configuration of the output switching means, when it is determined that the voltage of the selection signal is within the predetermined range, the configuration is such that power is supplied to the sensor mounted on the substrate, or the output of the sensor mounted on the substrate is There is a configuration for connecting to an output signal.

  The present invention can also be applied to various devices and electronic devices provided with the above-described sensor detection circuit. Specific examples include a recording device, a copying machine, and a multifunction device that perform recording on a recording medium. .

  According to the present invention, in a configuration in which the control board and each sensor board are cascade-connected by four signal lines, the sensor includes the voltage within a predetermined range according to the voltage of the selection signal output from the control board. The output from the sensor mounted on the substrate can be obtained.

  Therefore, the number of signal lines connecting the substrates can be reduced to four, and the output from the desired photosensor can be obtained by changing the voltage of the selection signal.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the components described in the following embodiments are merely examples, and are not intended to limit the scope of the present invention only to them.

  Further, in the following embodiment, the same reference numerals are used to denote the same parts as those shown in FIGS. 5 and 6 described with respect to the conventional example.

<First Embodiment>
FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of an optical sensor detection circuit according to the present invention. In the figure, 1 is a control board on which a CPU 10 for controlling the entire apparatus is mounted, 2 is a first photosensor board on which a first photosensor PI1 is mounted, and 3 is a second board on which a second photosensor PI2 is mounted. Each of the optical sensor substrates is shown.

  The control board 1 is provided with a 4-pin connector 11 for connection to the optical sensor board. The first optical sensor board 2 is provided with a 4-pin connector 21 for connection to the control board 1 and a 4-pin connector 22 for connection to the second optical sensor board 3. The second photosensor substrate 3 includes a 4-pin connector 31 for connection to the second photosensor substrate 2 and a 4-pin connector for connection to a third photosensor substrate (not shown). 32 is provided.

  In FIG. 1, only two photosensor substrates are shown, but a large number of photosensor substrates such as a third and a fourth can be connected by cascade connection.

  The pin arrangement of the connectors 11, 21, 22, 31, and 32 is the same, and cascade connection using a 4-pin parallel cable or the like is possible. Pin 1 is VCC, which is a terminal for a power source supplied to the circuit of the optical sensor substrate and the optical sensor. The second pin is a terminal for analog voltage output from the CPU 10. The third pin is a sensor output terminal to which the emitters of phototransistors (PTr1, PTr2) that are light receiving elements of the photosensors of each sensor substrate are connected, and the current of the phototransistor of the selected photosensor is controlled by the control substrate. 1 is detected by the resistor R and input to the CPU 10.

  The first optical sensor substrate 2 is provided with three resistors R11, R12, and R13 connected in series, and a reference voltage Vref11 for the comparator CMP1 is supplied from a connection point between the resistors R11 and R12. Similarly, the reference voltage Vref12 for the comparator CMP2 is supplied from the connection point of the resistors R12 and R13. The outputs of the two comparators CMP1 and CMP2 are connected in common to the other end of the resistor R1 whose one end is connected to the power supply, and further connected to the base of the transistor Tr1. Here, the two comparator outputs are open collectors. Therefore, when both of the two comparators CMP1 and CMP2 become high impedance, the current flows from R1 to the base of Tr1, and the transistor Tr1 is turned on.

  The collector of Tr1 is connected to transistor Tr2 via resistors R3 and R2. With this configuration, when Tr1 is turned on, Tr2 is also turned on, and when Tr1 is turned off, Tr2 is also turned off. LED1 is a photodiode that functions as a light emitting element of the optical sensor PI1, and a current limiting resistor R4 is connected in series. The phototransistor PTr1 and the photodiode LED1 constituting the photosensor are mounted facing each other when the photosensor PI1 is a transmissive sensor, and mounted in the same direction with respect to the detection target when the photosensor is a reflective sensor. The

  The second photosensor substrate 3 has a circuit configuration similar to that of the first photosensor substrate 2, but the values of the resistors R21, R22, and R23 are different from the values of the resistors R11, R12, and R13. Even when there is a third optical sensor substrate (not shown), the circuit configuration is the same, but the values of the three resistors connected in series are different.

  Here, a method of setting these three resistance values will be described with reference to FIG. As described with respect to the first photosensor substrate, the reference voltages Vref11 and Vref12 of the two comparators are determined by the ratio of the values of the three resistors R11, R12, and R13 connected in series.

  In the present embodiment, as shown in FIG. 3, each of the photosensors is arranged so that the two reference voltages of each photosensor substrate do not overlap with the reference voltages of the other photosensor substrates between GND and VCC. Determine the three resistance values of the substrate. FIG. 3 shows the reference voltage of each photosensor substrate when n photosensor substrates are cascade-connected. In this example, the reference voltages are set so as to be arranged at substantially equal intervals from Vref11 to Vrefn2.

  By setting each reference voltage in this way, only the desired optical sensor can be selectively driven.

For example, when the optical sensor PI1 of the first optical sensor board 2 is driven to detect its state, the value of the analog voltage V output from the analog port of the CPU 10 of the control board 1 is
Vref11 <V <Vref12
Set to the range. In this case, both of the two comparators CMP1 and CMP2 of the first photosensor substrate 2 become high impedance, and current flows through the base of the transistor Tr1 via the resistor R1. Then, the transistor Tr1 is turned on, the transistor Tr2 is also turned on, and the power supply VCC is supplied to the photosensor PI1.

On the other hand, in the second photosensor substrate 3,
V <Vref21 <Vref22
Therefore, the output of the comparator CMP1 is low impedance, and the output of the comparator CMP2 is high impedance. As a result, no current flows through the base of the transistor Tr1, Tr1 is turned off, and the transistor Tr2 is also turned off. Accordingly, the power supply VCC is not supplied to the optical sensor PI2.

  Similarly, in the third and subsequent photosensor substrates, Tr1 and Tr2 are turned off, and the power supply VCC is not supplied to the corresponding photosensors.

Similarly, when the optical sensor PI2 of the second optical sensor board 3 is driven and its state is detected, the value of the analog voltage V output from the analog port of the CPU 10 of the control board 1 is
Vref21 <V <Vref22
Should be set within the range.

  When driving the photosensors of the third and subsequent photosensor boards to detect the state, the value of the analog voltage V output from the analog port of the CPU 10 of the control board 1 according to the voltage range shown in FIG. Should be set.

  As described above, according to the optical sensor detection circuit of the present embodiment, the number of wirings between the control board and each sensor board is reduced to four, and output from the analog port of the CPU 10 of the control board 1. By setting the value of the analog voltage V within the voltage range assigned without overlapping each photosensor substrate, the corresponding photosensor can be driven to selectively detect the state.

<Second Embodiment>
Hereinafter, a second embodiment of the photosensor detection circuit according to the present invention will be described. FIG. 2 is a block diagram showing a schematic configuration of the second embodiment of the optical sensor detection circuit in the same manner as in FIG. 1, in which the same parts as in FIG. 1 described with reference to the first embodiment are shown. Are indicated by the same reference numerals.

  When this embodiment is compared with the first embodiment, the outputs of the two comparators CMP1 and CMP2 of each photosensor substrate are connected to the base of the transistor Tr1 in the first embodiment, whereas this embodiment is compared with the first embodiment. The embodiment is different in that it is connected to the channel select terminal A of the analog multiplexer 4. Further, since there is no transistor Tr2 in the path of the power supply VCC, the power supply VCC is always supplied to the photosensor in this embodiment.

  If the channel select terminal A is at a low level, the analog multiplexer 4 selects the data D0 and outputs the signal to the common terminal X. On the other hand, if the channel select terminal A is at the high level, the data D1 is selected and the signal is output to the common terminal X. Therefore, in this embodiment, when the channel select terminal A is at the high level, the emitter of the phototransistor PTr of the corresponding optical sensor is connected to the common terminal X, and the analog port of the CPU 10 of the control board 1 as the sensor output of the connector. Is input.

  In each optical sensor board, the values of two reference voltages determined by the ratio of the values of three resistors R11, R12, and R13 connected in series are shown in FIG. 3, as in the first embodiment. Set as follows. Thereby, the output from the corresponding optical sensor can be read in accordance with the value of the analog voltage V output from the analog port of the CPU 10 of the control board 1.

  As described above, according to the optical sensor detection circuit of the present embodiment, the number of wirings between the control board and each sensor board is reduced to four, and output from the analog port of the CPU 10 of the control board 1. By setting the value of the analog voltage V to the voltage range assigned without overlapping each photosensor substrate, the state of the corresponding photosensor can be selectively detected.

(Modification)
In the first and second embodiments, the values of the two reference voltages of each sensor board are set as shown in FIG. 3, but the settings of the values of the two reference voltages of each sensor board are as follows: It is not limited to this.

  For example, in the example of FIG. 3, the voltage range corresponding to the first photosensor PI1 is set to increase in order, but the voltage range corresponding to the first photosensor is set to the highest, and the subsequent voltage is set. The range may be set so that the range decreases in order. Further, if the CPU can determine the correspondence between the voltage range and the photosensor, it is not necessary to set the order according to the photosensor number.

  Also, it is not necessary to make the widths and intervals of each voltage range equal, and if the widths and intervals of each voltage range are set to such an extent that the voltage ranges do not overlap each other and are not erroneously recognized due to potential voltage fluctuations, etc. good.

<Other embodiments>
In the embodiment described above, the case where the present invention is applied to an optical sensor has been described as an example. However, the present invention is not limited to a sensor that outputs a signal corresponding to one of two values such as a high level and a low level. For example, the present invention can be applied to sensors other than the optical sensor.

  In addition, electronic devices, apparatuses, and systems using the above-described optical sensor detection circuit are also included in the scope of the present invention. Examples of electronic devices and apparatuses in which the optical sensor detection circuit according to the present invention is used include devices and apparatuses including movable parts such as a recording apparatus, a copying machine, a facsimile machine, and a multifunction machine. Further, examples of systems in which the optical sensor detection circuit according to the present invention is used include systems that perform mechatronics control of automobiles and the like in addition to systems including such devices and apparatuses.

It is a block diagram which shows the structure of 1st Embodiment of the optical sensor detection circuit which concerns on this invention. It is a block diagram which shows the structure of 2nd Embodiment of the optical sensor detection circuit based on this invention. It is a figure explaining the setting of the reference voltage of a some optical sensor board | substrate. It is a figure which shows the example of a connection of a control board and an optical sensor board | substrate in a common printer. It is a block diagram which shows the 1st example of the connection of the conventional control board and a some optical sensor board | substrate. It is a block diagram which shows the 2nd example of the connection of the conventional control board and a some optical sensor board | substrate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Control board 2, 3 Optical sensor board 4, 5 Analog multiplexer 6 Control circuit 11, 21, 22, 31, 32 Connector PI1-PI12 Optical sensor CMP1, CMP2 Comparator PTr1, PTr2 Phototransistor LED1, LED2 Photodiode

Claims (8)

A plurality of sensor boards each equipped with a sensor;
A control circuit that includes a control unit that outputs a selection signal for selecting any one of the sensors and receives an output signal from the sensor, and that supplies power to the plurality of sensor substrates. There,
In the control board and the plurality of sensor boards, power supply wiring, the selection signal, and the output signal are cascade-connected,
Each sensor board
Voltage range determining means for determining whether or not the voltage of the selection signal is within a predetermined range;
When the voltage range determination means determines that the voltage of the selection signal is within the predetermined range, the output range switching means for outputting the output of the sensor mounted on the substrate as the output signal ,
Each of the predetermined ranges corresponding to each of the plurality of sensor boards is set so as not to overlap with each other, and has a substantially equal size, and is set at a predetermined interval between the voltage value of the power source and GND. Yes,
A sensor detection circuit characterized by the above. The sensor detection circuit according to claim 1 , wherein the sensor is a sensor that outputs a signal corresponding to one of binary values. The sensor detection circuit according to claim 2 , wherein the sensor is an optical sensor. The voltage range determination means, sensor detection circuit according to any one of claims 1 to 3, characterized in that it comprises two comparators which corresponds to the upper limit and the lower limit of the predetermined range. The output switching means includes means for supplying power to a sensor mounted on the substrate when the voltage range determination means determines that the voltage of the selection signal is within the predetermined range. The sensor detection circuit of any one of Claims 1 thru | or 4 . The output switching means includes means for connecting an output of a sensor mounted on the substrate to the output signal when the voltage range determination means determines that the voltage of the selection signal is within the predetermined range. The sensor detection circuit according to any one of claims 1 to 5 . Apparatus characterized by comprising a sensor detection circuit according to any one of claims 1 to 6. The apparatus according to claim 7 , wherein the apparatus performs recording on a recording medium, and the sensor includes a sensor that detects a position of the recording medium.

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