JP2007181278A - Autonomous power supply and wireless sensor network apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an autonomous power supply and a wireless sensor network apparatus for implement indoor photovoltaic power generation, and supplying sufficient power. <P>SOLUTION: An electric double layer capacitor 210 stores a charge generated from a solar cell 110. When the solar cell 110 can not generate power, a reverse current preventing diode 280 prevents a reverse current from the electric double layer capacitor 210. A voltage detector 220 confirms a charged state of the electric double layer capacitor 210 as a voltage value. A real time clock 230 temporally controls an intermittent operation. A power supply switch 260 controls the supplied power by the logical sum of the voltage detector 220 and the real time clock 230. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The self-sustained power supply of the present invention and a wireless network device equipped with this self-supported power supply convert the light of the fluorescent lamp into electrical energy, store the generated charge, and use the stored charge as necessary to It belongs to the field of power generation devices to be driven and the technical field of communication devices that are mounted on wireless sensor network devices and digitize environmental changes using sensors, and communicate those values on radio waves.

  Speaking of a wireless sensor network, it is generally driven using a household AC power source, a battery typified by a coin battery or a storage battery (for example, see Patent Document 1). There is a growing technical appreciation of how long the same battery can be used.

  On the other hand, a radio device used outdoors often generates power using a solar cell, and a method of using the generated electric charge in a secondary battery is often used. Since the amount of power generated by the solar cell is determined by the power generation efficiency and the luminous flux density with respect to the wavelength of the solar cell, it is generally designed to ensure a sufficient amount of power generated outdoors even on a cloudy day.

  However, the wireless sensor network is generally operated indoors, and when a self-sustained power supply is installed, a photovoltaic device that matches indoor light is required. Similarly, there is a large difference in light density between outdoors and indoors, and it is necessary to generate power with weak light in the room. As an example, in a solar cell standard, an outdoor solar cell has a reference minimum incident light amount of 50,000 lux, whereas an indoor solar cell has a reference minimum incident light amount of 200 lux. That is, there is a 250 times difference between the two.

Next, as for the secondary battery, a secondary battery such as a nickel metal hydride battery having a capacity larger than that of the nickel cadmium battery is commercially available. However, some have a memory effect, and if you repeat charging and discharging, the capacity will drop rapidly, and depending on how you use it, the capacity will drop in half in half a year. Also, many of them are large in size and weight, and are not necessarily suitable for making a small wireless sensor network device.
JP 2005-545695 A

  It is a problem to be solved by the present invention to generate photovoltaic power indoors and supply sufficient power to the wireless sensor network device. In considering the size of the device itself, the size of the noun size is the limit, even if it is large, considering that the size does not give a sense of incongruity to daily life. On the other hand, the light intensity in the room is generally 300 lux at the conference room or office room and at most 600 lux, and there is a report that it is 200 lux or less in other places, for example, cafeteria and cafe room. is there. Therefore, it is one of the problems to adopt the maximum power generation efficiency with the minimum light quantity obtained from the fluorescent lamp in the room being 200 lux and the wavelength of 800 nm (nanometer) of a white fluorescent lamp having a noun size or less. Next, as a device for storing the output of the solar cell, there is a problem of developing a power storage device that does not have a memory effect and that does not have a significant decrease in capacity due to repeated charging / discharging or changes over time.

  The self-supporting power supply device of the present invention prevents a backflow current from the electric double layer capacitor when the solar cell, the electric double layer capacitor that accumulates the electric power generated by the solar cell, and the solar cell can no longer generate electric power. A reverse current prevention diode, a voltage detector for confirming a charge state of the electric double layer capacitor by a voltage value, a real time clock for controlling intermittent operation by time, and a logical sum from the voltage detector and the real time clock The power supply switch for controlling the power supply by the power supply and the voltage controller for controlling the voltage to the load unit.

In the self-supporting power supply device of the present invention, the power switch controls the power supply voltage by the voltage controller by turning on when the voltage detector is on and the real time clock is on.
The wireless network device of the present invention includes the above-described self-supporting power supply device, and includes a movable device that changes the angle of the solar cell in order to maximize the amount of power generated by the solar cell.

  Unlike a general battery such as a dry battery or a wireless sensor network device driven by a battery, power generation by a solar cell can prevent the wireless network from being stopped due to battery consumption. In addition, by using an electric double layer capacitor without using a conventional secondary battery, capacity reduction due to deterioration over time can be suppressed. Therefore, there is an advantage that the number of maintenance or the cost due to the replacement of the power storage device can be reduced due to the capacity reduction. Furthermore, when the amount of power generation is insufficient and a sufficient amount of electricity is not stored in the wireless sensor network in the power storage device, charging can be performed in a non-contact manner. That is, it has the effect of reducing maintenance.

  The present invention will be described with reference to the drawings.

FIG. 1 shows the external shape of a wireless sensor network device equipped with the self-supporting power supply device of the present invention. A solar cell 110 is laid on the surface of the device 100. The sensor is stored in the sensor unit 120 of FIG. 1, and free circulation of outside air is ensured. When a test such as confirmation of the communication state is performed, a communication state display unit 130 is provided to indicate the state, and the light emitting diodes are composed of three colors. The lighting of the red light emitting diode indicates the time of transmission, the lighting of the yellow light emitting diode indicates the time of reception, and the green light emitting diode indicates the time of processing of the central processing unit. The communication status display unit 130 does not normally emit light and is lit only when a test or demonstration is performed. In addition, a movable table 140 is provided on the side of the device, and has a structure that can change the set angle of the solar cell.
Next, a method for efficiently converting a self-supporting power supply device using a solar cell panel and an electric double layer capacitor to a power source of a wireless sensor network device will be described.

  In order to use the self-supporting power supply device 200 combining the solar cell 110 and the electric double layer capacitor 210 as the power source of the wireless sensor network device 100, attention must be paid to the following two points. First, since the working voltage of the wireless sensor network 100 is 3.3V, it is necessary to keep 3.3V as the output voltage. In addition, since the output current of the solar cell 110 is much smaller than the amount of current used by the wireless sensor network 100, the power supply must be turned on intermittently.

  FIG. 2 is a circuit diagram showing the self-supporting power supply device of the present invention. This circuit includes a solar cell 110 that converts fluorescent light into electricity, an electric double layer capacitor 210 that stores the generated electric charge, and a backflow from the electric double layer capacitor 210 when the incident light does not exist and the solar cell 110 cannot generate electricity. A reverse current prevention diode 280 for preventing current, a voltage detector 220 for confirming a charging state of the electric double layer capacitor 210 by a voltage value, a real time clock 230 for controlling intermittent operation by time, an output and a real time of the voltage detector 220 The circuit includes a mini-logic circuit 270 that performs a logical sum of outputs of the clock 230, a power switch 260 that controls power supply by the output of the logic circuit 270, and a voltage controller 240 that controls the voltage to the load unit 250.

  Unlike the outdoor solar cell, the indoor solar cell has a maximum wavelength of 800 nm, and the amorofas silicon solar cell 110 having the maximum power generation efficiency at this wavelength is used. Using. In order to keep the size of the wireless sensor network device 100 below the noun size, a 9-cell amorphous silicon type solar cell with a glass top surface of about 58 cm wide and about 45 cm long was used. The release voltage of the solar cell 110 is about 5 V, the short-circuit current is about 47 μA, and the good output efficiency is 42 μA at 3.0 V. The reference power amount (hereinafter referred to as “reference power amount”) supplied to the wireless sensor network device 100 is 330 mF (millifarads). However, the power storage device has a spontaneous discharge and the like, and the power storage device of 470 mF is used in consideration of capacity loss. An electric double layer capacitor 210 was used as a type of power storage device in order to prevent a decrease due to a change in capacity over time.

When a solar cell 110 having a voltage of 3V and a current of 42 μA is used to charge a 470 mF electric double layer capacitor, it takes about 62 minutes even if there is no charge loss. For this reason, when the solar cell 110 and the electric double layer capacitor 210 of the present invention are used, it is difficult to always keep the wireless sensor network device 100 connected to the power supply in an operating state. In this case, in order to normally operate the wireless sensor network device 100 equipped with the self-supporting power supply device of the present invention, when the wireless sensor network device 100 operates, sufficient electric power is accumulated in the electric double layer capacitor 210. And a structure related to the exterior that increases the amount of power generation in a weak light environment such as indoors, and a method of charging this stand-alone power supply device to supplement power generation when sufficient electricity cannot be generated Become.
In addition, as an amount of power for supplying sufficient power to the wireless sensor network device 100, an applied voltage of 3.3 V, a consumption current of 10 mA, and a duration of 10 seconds were used as a guide.

  In consideration of the breakdown voltage, a reverse current prevention diode 280 having a breakdown voltage of 10 V and a drop voltage of 0.2 V was used. The voltage detector 220 assumes that the output voltage to the load unit 250 is 3.3 V and assumes that there is a voltage fluctuation in the power supply due to a change in the load, and has a margin with respect to the load voltage. Set to 7V. As the power switch 260, a semiconductor type switch was implemented as a contact type switch. The semiconductor type has a small amount but may have a leakage current. In this respect, the contact type switch is good, but the contact switch requires a large drive circuit. A voltage control circuit 240 having an output voltage of 3.3 V was used.

  Next, the load part is shown. FIG. 3 is a schematic diagram showing the configuration of the load portion. The load unit 250 includes a wireless module 310 that exchanges information at a high frequency, a central processing unit 320 that processes information, a temperature / humidity meter 330 that measures temperature and humidity, and a second real-time clock 340 that manages time such as communication time. There is. The central processing unit, the temperature / humidity meter, and the second real time clock 340 are connected by an IIC (Isquare Sea) interface 360. The temperature / humidity meter 330 is a C-MOS (Complementary Metal Oxide Semiconductor) type temperature / humidity sensor, which consumes very low power and has a level of several μA.

  In the power control by this method, the power switch 260 is not turned on when the electric double layer capacitor 210 is not sufficiently charged by taking the logical sum of the outputs of the voltage detector 220 and the real time clock 230. Therefore, there is no worry that the power will be cut off during the work. In addition, since the power is not turned on even when the real time clock 230 is turned on, in the case of a multi-hop communication system, communication is performed ignoring the device 100, and the device 100 is broken or has some problem. There is an advantage that it can be grasped through the network.

The operation of the self-supporting power supply apparatus 200 of the present invention will be described. FIG. 7 shows a flowchart when the self-supporting power supply 200 supplies power. If there is incident light, the solar cell 110 generates power (step 101). The generated current passes through the reverse current prevention diode 280 (step 102), and the electric double layer capacitor 210 is charged (step 103). The voltage of the electric double layer capacitor 210 increases every time it is charged (step 104), and when the set voltage reaches 3.7V (step 1101), its output is turned on (step 105). On the other hand, when it is time to operate the wireless sensor network device 100 of the present invention (step 1102), the real time clock 230 is turned on (step 106), and the value is input to the OR circuit (step 107). The power switch 260 is turned on (step 108). When the power switch 260 is turned on, the electric charge charged in the electric double layer capacitor 210 flows (step 109), and the voltage controller 240 controls the power supply voltage to 3.3 V and flows it to the load unit 250 (step 110). .
Next, an exterior structure that maximizes power generation efficiency will be described.

In the case of generating power under the weak light of the fluorescent lamp 410, the solar battery 110 is not installed unless the light 430 of the fluorescent lamp 410 strikes the right angle with respect to the solar battery surface of the wireless sensor network device 100 with a self-supporting power source. The power generation capability you have cannot be fully demonstrated.
With respect to the fluorescent lamp 410 attached to the ceiling, the angle between the device stand 420 and the surface of the solar cell 110 is varied, and the amount of electromotive force is measured. Then, when the value of the angle of the surface of the solar cell 110 perpendicular to the optical axis of the fluorescent lamp 410 is 1, the amount of power generation changes with a value close to a cosine function. This is because the power generation amount in the solar cell 110 is changed because the light beam density is changed by changing the angle of the light beam incident on the surface of the solar cell 110. Therefore, in order to obtain a larger amount of power generation, it is necessary to set the surface of the solar cell 110 of the wireless sensor network device 100 so as to always face the optical axis direction from the fluorescent lamp 410. In addition, since the light flux density decreases in inverse proportion to the square of the distance, it is necessary to select the same fluorescent lamp 410 that is close to this device.

When the self-sustained power supply wireless sensor network device 100 of the present invention is placed on a desk or the like, the movable base 140 shown in FIG. 1 is moved to set the position so that the amount of power generation is maximized. It is possible to secure the electric power necessary for use by the load unit 250 shown in FIG.
FIG. 4 is a schematic diagram showing how the movable base 140 is moved to maximize the luminous flux density of incident light from the fluorescent lamp 410. In this figure, it is assumed that this device is placed on a desk on which a human works.

  A description will be given of a method of charging the emergency power supply device for emergency use when the wireless sensor network cannot operate sufficiently due to insufficient input light and the wireless sensor network stops operating. FIG. 5 shows the structure of the charging device, and FIG. 6 is a schematic diagram showing the state when optical charging is performed.

  The wireless sensor network device 100 equipped with the self-supporting power supply device 200 of the present invention is installed in various places. As an example in the room, the surface of the ceiling, the side of the wall, the desk, etc. can be considered. Of these, the surface of the ceiling and the upper surface of the wall are places that are difficult for human hands to reach. Charges can be replenished easily with a charger if it is within reach of human hands, but in places where it is difficult to reach, use a stepladder or other tools to move to reach the reach. Must. Therefore, it may be necessary to outsource to a maintenance specialist, resulting in costly maintenance.

  On the other hand, since the self-supporting power supply device 200 of the present invention has a photovoltaic power generation system, the solar cell 110 generates power and replenishes the electric double layer capacitor 210 with charge as long as light necessary for power generation is supplied. become. Therefore, it is only necessary to prepare a light source necessary for power generation to replenish charges.

  As the solar cell 110 mounted on the self-supporting power supply device 200 of the present invention, a solar cell having a maximum power generation efficiency at a wavelength of 800 nm is used. The wavelength of 800 nm is strong even in the spectrum emitted by the white fluorescent lamp 510. Accordingly, an optical charging device 500 using the white fluorescent lamp 510 as a light source has been developed and used as a charger for the self-supporting power supply device of the present invention. Next, this charging device will be described.

  First, the white fluorescent lamp 510 used for the light source is preferably small, for example 20 watts or less, in consideration of carrying. In this embodiment, a 20 watt white fluorescent lamp 510 was used in consideration of the light intensity. The structure of the white fluorescent tube was not a normal straight tube, but a curved tube was used at first glance. Next, a parabolic metal plate 520 is arranged behind the white fluorescent tube 510 in order to condense and give directionality to the light, and the back thereof is fixed by a hinge 530, and the parabolic metal plate 520 and the white fluorescent tube are fixed. 510 was able to swing his head vertically. Below the hinge 530 was a support column 540, and a weight was incorporated in the lower part to stabilize it.

  The optical charger 500 is characterized by a very simple structure and low manufacturing costs. As for the method of use, the optical charger 500 is simply placed on a desk or the like, and light is only irradiated toward the solar cell surface of the wireless sensor network device 100 to be charged. In the charging experiment in this example, charging was completed in about 40 minutes.

  The real-time calibration method of the present invention has utility value as a useful method for constructing a maintenance-free wireless sensor network, and is a special device that is connected to the network but cannot obtain time information from the outside. It can be used for real-time calibration.

Schematic diagram showing the appearance of a self-supporting power supply Schematic diagram showing the electrical circuit of a self-supporting power supply Schematic diagram showing the configuration of the load section Relationship between the direction of the fluorescent lamp and the angle of the device Schematic diagram showing the shape and function of the optical charger Method for charging wireless sensor network device using optical charger Flow chart of independent power supply

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Wireless sensor network apparatus 110 Solar cell 120 Sensor part 130 Communication state display part 140 Movable stand 210 Electric double layer capacitor 220 Voltage detector 230 Real time clock 240 Voltage controller 250 Load part 260 Power switch 270 Mini logic circuit 280 Prevention of reverse electricity Diode 410 Fluorescent lamp 420 Device stand 500 Optical charger 510 White fluorescent lamp 520 Parabolic metal plate 530 Hinge

Claims (4)

Solar cells,
An electric double layer capacitor for storing electric charges generated by the solar cell;
A reverse current prevention diode for preventing a reverse current from the electric double layer capacitor when the solar cell cannot generate electricity;
A voltage detector for confirming a charge state of the electric double layer capacitor by a voltage value;
A real-time clock that controls intermittent operation by time;
A power switch for controlling power supply by a logical sum from the voltage detector and the real time clock;
A self-supporting power supply device comprising a voltage controller for controlling the voltage to the load section.   2. The self-supporting power supply apparatus according to claim 1, wherein the power switch controls the power supply voltage by the voltage controller when the voltage detector is on and the real time clock is on.   A wireless network device comprising the self-supporting power supply device according to claim 1.   The wireless network device according to claim 3, further comprising a movable device that changes an angle of the solar cell in order to maximize a power generation amount of the solar cell.

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