JP3829662B2 - Optical input converter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical input conversion device that can obtain an output corresponding to the amount of incident light.
[0002]
[Prior art]
Conventionally, this type of light input conversion device is attached to a ceiling, for example, and is used for detecting the illuminance on the desk surface directly below. The optical input conversion device 1 shown in FIG. 8 includes a light receiving element 4 on which light reflected from a desk surface is incident. After the output of the light receiving element 4 is amplified by the amplifier circuit 5, the output value of the amplifier circuit 5 is converted to a microcomputer. 6. A / D conversion is performed by 6 and the offset value set by the offset correction switch 7 is subtracted from the output value of the amplification circuit unit 5 in the microcomputer 6 to obtain a calculated value and this calculated value is output to the outside. is doing. In the illustrated example, a light receiving element 4 that outputs a current corresponding to the amount of incident light like a photodiode is used. Since the output current of this type of light receiving element 4 is very weak, the amplifier circuit unit 5 amplifies the voltage after converting the output of the light receiving element 4 to current. Further, in the illustrated example, the optical input conversion device 1 is connected to the parent device 2 via the signal line 3, and is configured to return the above-described calculation value to the parent device 2 when requested by the parent device 2. Yes. By using such a configuration, the base unit 2 can obtain the desk surface illuminance based on the calculated value returned from the light input conversion device 1 in order to control a load such as an illumination load. Here, since the light receiving element 4 provided in the light input conversion device 1 detects the reflected light on the desk surface, the base unit 2 has a constant for converting the amount of light incident on the light receiving element 4 into the desk surface illuminance. Is registered in advance, and the base unit 2 calculates the desk surface illuminance by multiplying the calculated value from the light input conversion device 1 by the constant.
[0003]
By the way, since the desk surface illuminance is obtained by multiplying the calculated value output from the light input conversion device 1 by a constant as described above, the calculated value must also be 0 when the desk top illuminance is zero. That is, if the calculated value is not 0 in the dark state where the desk top illuminance is 0, the desk top illuminance obtained by the master unit 2 does not become 0, and the correct desk top illuminance cannot be obtained. On the other hand, in order to perform the above-described current-voltage conversion and voltage amplification in the amplifier circuit unit 5, an operational amplifier is often used in the amplifier circuit unit 5, and it is known that there is an offset voltage in which the output does not become 0 when the input is 0. Therefore, in order to accurately obtain the desk surface illuminance in the master unit 2, the offset voltage must be removed from the calculated value output from the light input conversion device 1.
[0004]
Therefore, the optical input conversion device 1 described above is provided with an offset correction switch 7 for generating an offset value corresponding to the offset voltage from the output value of the amplifier circuit unit 5, and the offset value set by the offset correction switch 7 is changed. The microcomputer 6 subtracts it from the output value of the amplifier circuit unit 5 and uses it for the calculated value. The offset correction switch 7 is a 4-bit digital switch (for example, a DIP switch), and can select each value obtained by dividing the range from 0 V to the assumed maximum offset voltage value into 16 stages. Therefore, a value closest to the offset voltage included in the output value of the amplifier circuit unit 5 is selected from values that can be selected by the offset correction switch 7, and the microcomputer 6 uses this value as the offset value.
[0005]
[Problems to be solved by the invention]
However, when the offset value is set by using the offset correction switch 7 as described above, the offset value is selected from a relatively small number of stages (16 stages in the above example). Although it is possible to select an offset value close to the offset voltage included in, it is difficult to match the offset voltage with the offset value. In order to solve this problem, it is conceivable to increase the number of stages that can be selected by the offset correction switch 7. However, as the number of stages increases, the number of steps for selecting the optimum offset value increases. Also, setting the offset value manually increases the possibility of incorrect setting.
[0006]
The present invention has been made in view of the above reasons, and its purpose is to facilitate the setting of an offset value by automatically obtaining an optimum offset value, and consequently to select an offset value from multiple stages. An object of the present invention is to provide an optical input conversion device capable of setting an offset value with higher accuracy than the conventional configuration.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a light receiving element whose output changes according to the amount of incident light, an amplifier circuit section for amplifying the output of the light receiving element, and an output of the amplifier circuit section in a state where light to the light receiving element is blocked. A storage means for storing a value as an offset value, an operation switching pattern comprising two lands formed apart from each other, an offset process for storing the offset value in the storage means, and the above-mentioned at the time of incidence of light A microcomputer that performs one of the normal processing used as a calculation value by subtracting the offset value from the output value of the amplification circuit unit depending on whether the land of the operation switching pattern is open or short-circuited It is.
[0012]
The invention of claim 2 is characterized in that, in the invention of claim 1, an indicator lamp is provided for informing the end of the offset processing.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention and reference examples related to the present invention will be described below with reference to the drawings.
( Reference Example 1)
As shown in FIG. 1, the light input conversion device 1 in this reference example uses a light receiving element 4 whose output changes according to the amount of incident light, amplifies the output of the light receiving element 4 by the amplifier circuit unit 5, and then amplifies the amplification circuit. This is the same as the conventional configuration in that the output value of the unit 5 is input to the microcomputer 6. However, in this reference example , an EEPROM 8 as a storage means is attached to the microcomputer 6, and an operation changeover switch 9 for selecting an offset process and a normal process described later is attached to the microcomputer 6.
As the light receiving element 4, an element whose output current changes according to the amount of incident light is used as in the conventional configuration. As shown in FIG. 2, the amplifier circuit unit 5 includes a current-voltage conversion unit 5a and a voltage amplification unit 5b. The current-voltage conversion unit 5 a includes an operational amplifier 10 and a resistor 11, and outputs a voltage corresponding to the output current of the light receiving element 4 when the output current of the light receiving element 4 is input to the inverting input terminal of the operational amplifier 10. The voltage amplifier 5b is a non-inverting amplifier circuit including an operational amplifier 12 and two resistors 13 and 14, and amplifies the output voltage of the current-voltage converter 5a.
[0014]
By the way, the microcomputer 6 of this reference example is configured to select the offset process and the normal process in accordance with the setting state of the operation selector switch 9. Basically, the offset process is a process of writing the output value of the amplifier circuit unit 5 into the EEPROM 8 as an offset value, and the normal process is to read the offset value stored in the EEPROM 8 and subtract it from the output value of the amplifier circuit unit 6. It is processing. Hereinafter, the operation of the microcomputer 6 will be specifically described with reference to FIG.
[0015]
When the optical input converter 1 is turned on (S1), the microcomputer 6 is initialized (S2), and then the setting state of the operation changeover switch 9 is read (S3). Here, when the operation switch 9 is on, the process shifts to an offset process, and when it is off, the process shifts to a normal process. As described above, since the offset value needs to be stored in the EEPROM 8 in the normal process, the offset process for registering the offset value in the EEPROM 8 will be described first.
[0016]
When the operation switch 9 is turned on before the power is turned on and the process proceeds to the offset process in step S3, the counter X is first initialized to 0 (S4), and the output of the amplifier circuit unit 5 is read three times (S5 to S7). ). The “light input conversion value” in FIG. 3 means the output value of the amplifier circuit unit 5. After the output value of the amplifier circuit unit 5 is read three times, the process proceeds to step S8, and an average value of the three light input conversion values is obtained. The average value thus obtained is stored in the EEPROM 8 as an offset value (S9). When the offset value is stored in the EEPROM 8 in this way, the offset process is finished. There is little time between them.
Here, since the offset value is a value corresponding to the offset voltage generated in the amplifier circuit unit 5, it is necessary to execute the offset process in a state where no light enters the light receiving element 4. Therefore, the above-described processing is executed by storing the light input conversion device 1 in a light-shielded box. Here, the microcomputer 6 does not shift to the normal process during the offset process even if the state of the operation selector switch 9 is changed, and the normal process is not performed until the power is turned on after the offset process is completed. It is made not to be broken. Thus, an offset value is automatically set in the EEPROM 8 if the power is turned off after a few seconds have passed since the operation switch 9 was turned on and the power was turned on.
[0017]
On the other hand, when the light input conversion device 1 is actually used to measure the illuminance on the desk surface, the operation switch 9 is turned off and the light input conversion device 1 is installed in the actual use environment and the power is turned on. (S1). Also in this case, after the initialization process of the microcomputer 6 is performed (S2), the setting state of the operation selector switch 9 is read in step S3, and the process proceeds to the normal process. In the normal process, first, an offset value is read from the EEPROM 8 (S11). Thereafter, the output value (light input conversion value) of the amplifier circuit unit 5 is read (S12), and the offset value is subtracted from the light input conversion value to obtain a correction value (calculation value) (S13). When this correction value is used, for example, as described in the conventional configuration, it is possible to perform calculation processing for obtaining the desk surface illuminance (S14), and to control the light output of the illumination load so as to keep the desk surface illuminance at a constant value. Such control processing becomes possible (S15). Thereafter, the microcomputer 6 repeats steps S12 to S15 in order to perform calculation processing and control processing in response to a change in the amount of light incident on the light receiving element 4. Since the offset value does not change here, the offset value is read only once in step S11, and the offset value is not read in the subsequent processing. In the normal process, even if the setting state of the operation changeover switch 9 changes, the process does not shift to the offset process. That is, the normal process and the offset process are independent, and an instruction to start the other process is not accepted during one process.
[0018]
As described above, in the configuration of this reference example , it is possible to automatically set the offset value by simply turning on the power by turning on the operation switch 9 while blocking the incidence of light on the light receiving element 4. Even if the number of bits of the EEPROM 8 is increased, the setting process of the offset value does not take time and no erroneous setting occurs. As a result, the offset value can be set in multiple stages as compared with the conventional configuration using the offset correction switch, and an accurate offset value about the resolution of the output value of the amplifier circuit unit 5 can be set. In particular, in this reference example , not only the offset voltage generated in the amplifier circuit unit 5 but also the error component due to the dark current of the light receiving element 4 is folded into the offset value, so that it is possible to obtain an accurate calculation value with little error. Become.
[0019]
Although an example in which the EEPROM 8 is used as the storage means has been shown, any memory in which the stored contents are not erased even when there is no power supply may be used. For example, a flash memory may be used.
(Embodiment)
In the first embodiment, the operation changeover switch 9 is used . However , in this embodiment, as shown in FIG. 4, the operation changeover pattern 15 is formed on the circuit pattern of the circuit board of the optical input change device 1. and in place of the operation switching switch 9. That is, the operation switching pattern 15 includes two lands 15a and 15b that are formed apart from each other. One of the lands 15a is connected to the microcomputer 6 and is connected to one end of the resistor R connected between both ends of the power source. Is connected to the other land 15b. Accordingly, the operation switch 9 can be used in an equivalent manner depending on whether the lands 15a and 15b are open or short-circuited, and the power source can be connected in a state where the lands 15a and 15b are short-circuited. If the microcomputer 6 is configured to perform the offset process when it is turned on, the operation changeover switch 9 becomes unnecessary. In the present embodiment, to set the offset value by performing an offset process using an inspection jig for shorting both lands 15a, the inter-15b before the factory, may be shipped by removing the test jig, the operation switch Since it is not necessary to mount the switch 9 on the circuit board, the number of parts is reduced, which contributes to cost reduction.
[0020]
In this embodiment and Reference Example 1 , the optical input conversion value is read three times during offset processing, and the average value is used as the offset value. However, the number of times the optical input conversion value is read is not particularly limited. The input conversion value may be read only once and used as an offset value.
( Reference Example 2)
In the reference example 1, execution of offset processing is instructed by turning on the operation switch 9 or bringing an inspection jig into contact with the operation switching pattern 15, and in principle, the offset processing is performed at the time of shipment. Even if an appropriate offset value is set at the time of shipment, the offset voltage fluctuates due to secular change, and the error component increases. Therefore, this reference example shows an example in which offset processing can be performed with a relatively simple operation even after shipment from the factory.
[0021]
As shown in FIG. 5, in this reference example , instead of the operation changeover switch 9 in the reference example 1, a wireless signal receiving unit 16 and an offset for receiving a wireless signal from a remote controller (hereinafter abbreviated as a remote control) provided separately. An LED lighting unit 17 having a light-emitting diode as an indicator lamp for notifying the end of processing is provided. Further, in the present reference example , as shown in FIG. 6, an input changeover switch 18 for selecting a state where the output of the light receiving element 4 is input to the amplifier circuit unit 5 and a state where the output is not input to the amplifier circuit unit 5 is provided. 5 is provided. The input changeover switch 18 has a common contact c connected to the input end of the current-voltage converter 5a, and the common contact c is selectively connected to one of the contact a connected to the light receiving element 4 and the contact b grounded. Connected. Further, the microcomputer 6 instructs whether the common contact c is connected to the contact a or the contact b. However, in this reference example, it is assumed that the common contact c is always connected to the contact a. Further, the microcomputer 6 of the present reference example is configured to be able to instruct the microcomputer 6 to start the offset process and the normal process by the output from the wireless signal receiving unit 16 based on the wireless signal from the remote controller. .
[0022]
As shown in FIG. 7A, when the power is turned on (S1), the microcomputer 6 automatically starts the normal process after the initialization process (S2) and reads the offset value stored in the EEPROM 8 (S11). ). The normal process is the same as in Reference Example 1, and the optical input conversion value is read (S12), and the value obtained by subtracting the offset value from the optical input conversion value is used as the correction value (calculated value) (S13). The calculation process (S14) and the control process (S15) are performed by using them.
[0023]
On the other hand, in order to start offset processing in this reference example , a remote controller (not shown) is operated during the normal processing period to start the offset processing. That is, when the wireless signal receiving unit 16 receives a wireless signal instructing the start of offset processing during the normal processing period, the normal processing is interrupted, and the offset processing is executed as interrupt processing as shown in FIG. The
The contents of the offset process are the same as those in Reference Example 1. First, the counter is initialized (S4), and the output value (optical input conversion value) of the amplifier circuit unit 5 is read three times (S5 to S7). Here, at the start of the interrupt processing, the common contact c of the input changeover switch 18 is connected to the contact b, and the output from the light receiving element 4 is not input to the amplifier circuit unit 5. In other words, since the input terminal of the amplifier circuit unit 5 is grounded and kept at the reference potential, the output value of the amplifier circuit unit 5 is a value that simulates the dark state regardless of the amount of light incident on the light receiving element 4. After the output value of the amplifier circuit unit 5 is read three times, an average value of them is obtained as an offset value (S8), and the offset value is written in the EEPROM 8 (S9). Here, after the offset value is written in the EEPROM 8, the LED lighting unit 17 is instructed to light the indicator lamp.
When the above-described offset processing ends, the interrupt processing ends and returns to normal processing. At the same time, the common contact c of the input changeover switch 18 is connected to the contact a. In this normal processing, since the latest offset value written in the EEPROM 8 is used, even if the offset voltage changes due to aging, an offset value corresponding to the offset voltage can be set. When returning from the offset process to the normal process, the common contact c of the input changeover switch 18 is connected to the contact b, and the output of the light receiving element 4 is input to the amplifier circuit unit 5.
[0024]
As described above, in the configuration of this reference example , the offset value can be set by a simple operation by operating the remote controller and instructing the start of the offset process, and provided separately from the optical input conversion device 1. Since the offset process can be instructed from the remote controller, the offset value can be easily changed after shipment from the factory. In addition, the provision of the input changeover switch 18 makes it possible to easily perform the offset value setting operation in that it is not necessary to block the light input to the light receiving element 4. In addition, the LED lighting part 17 can also be provided in the structure of the reference example 1 and embodiment .
[0025]
【The invention's effect】
According to a first aspect of the present invention, there is provided a light receiving element whose output changes according to the amount of incident light, an amplifier circuit section for amplifying the output of the light receiving element, and an output of the amplifier circuit section in a state where light to the light receiving element is blocked. A storage means for storing a value as an offset value, an operation switching pattern comprising two lands formed apart from each other, an offset process for storing the offset value in the storage means, and the above-mentioned at the time of incidence of light A microcomputer that performs one of the normal processing used as a calculation value by subtracting the offset value from the output value of the amplification circuit unit depending on whether the land of the operation switching pattern is open or short-circuited The output value of the amplifier circuit section in the light-shielded state is stored in the storage means as an offset value, and this offset value is read and used for correction. The offset value can be set easily by automatically obtaining the correct offset value, and as a result, the offset value can be selected from multiple stages, and the offset value can be set with higher accuracy than the conventional configuration. There is. In addition, the number of parts is reduced compared to the case of providing a switch for switching the operation of the microcomputer, which contributes to cost reduction.
[0030]
According to a second aspect of the present invention, in the first aspect of the invention, since the indicator lamp for notifying the end of the offset process is provided, the offset value is set by notifying the user of the end of the offset process. It can be easily confirmed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a reference example 1 related to the present invention.
FIG. 2 is a main part circuit diagram of the above.
FIG. 3 is an operation explanatory diagram of the above.
FIG. 4 is a block diagram showing an embodiment of the present invention .
FIG. 5 is a block diagram showing a reference example 2 related to the present invention.
FIG. 6 is a main part circuit diagram of the above.
FIG. 7 is an operation explanatory diagram of the above.
FIG. 8 is a block diagram showing a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Optical input converter 4 Light receiving element 5 Amplifying circuit part 6 Microcomputer 8 EEPROM
9 Operation changeover switch 15 Operation change pattern 15a, 15b Land 16 Wireless signal receiving part 17 LED lighting part 18 Input changeover switch

Claims (2)

A light receiving element whose output changes according to the amount of incident light, an amplifier circuit section that amplifies the output of the light receiving element, and an output value of the amplifier circuit section in a state where light to the light receiving element is blocked is stored as an offset value Storage means, an operation switching pattern composed of two lands formed apart from each other, an offset process for storing the offset value in the storage means, and an output value of the amplification circuit unit at the time of incidence of light An optical input conversion comprising: a microcomputer that performs one of the normal processing used as a calculation value by subtracting the offset value depending on whether the land of the operation switching pattern is open or short-circuited apparatus. The light input conversion device according to claim 1, further comprising an indicator lamp that notifies the end of the offset processing .

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