JP2008059516A - Active radio tag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and lightweight active radio tag capable of stably starting even when a power capacity is low in starting a power supply of an MCU. <P>SOLUTION: The radio tag is provided with the MCU 4, a power supply consisting of a lithium ion battery 1 and a DC-DC converter 2, a communication part consisting of a radio part 5 and an antenna 6, an LED, and an actuator 7 such as a motor. The radio tag is also provided with a voltage detector 3 and a delay circuit 13 as means for inputting a reset signal of the MCU 4 after a lapse of predetermined time when a power supply voltage of the MCU 4 is increases to a fixed reference voltage above a minimum operating voltage of the MCU 4 in starting the power supply. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an active wireless tag, and more particularly to its configuration and resetting method.

  An RFID (Radio Frequency Identification) system that reads and writes information in a non-contact manner by a reader / writer from a wireless tag in which predetermined information is stored is a product distribution, management, inspection, etc. as disclosed in Patent Document 1. Are used in various fields.

  A passive wireless tag that does not have a power source communicates using an electromotive force induced by an electromagnetic wave transmitted from a reader / writer, and thus has a very short communicable distance. Therefore, when a communication distance is required, an active wireless tag having a power source is used. Here, since the wireless tag is used by being mounted on an article, the wireless tag is required to be small and light, and to be inexpensive. Therefore, it is necessary to reduce the circuit scale and the power supply capacity as much as possible even for an active wireless tag having a power supply.

JP 2000-85975 A

  FIG. 6 shows a basic block configuration of a conventional active wireless tag. As shown in FIG. 6, the communication unit 15, the MCU (microcontroller unit) 14 that stores its own ID and controls communication, and the power supply unit 12 that supplies power necessary for these operations are large. Can be separated. Here, the commonly used MCU 14 has a built-in power-on reset function. When the power supply voltage of the MCU 14 reaches the lower limit value (minimum operating voltage) of the operating voltage after the power is turned on, the MCU 14 is initialized once. The reset operation starts automatically. For this reason, when the power supply capacity of the wireless tag is small, this reset operation becomes a load, and the power supply voltage may fall below the minimum operation voltage again, which may cause malfunction.

  FIG. 7 shows the difference in the rise time of the power supply voltage due to the difference in power supply capacity. As the power supply capacity is reduced to reduce the size and weight of the wireless tag, once the power supply voltage decreases and falls below the minimum operating voltage, it may take time to recover to the minimum operating voltage, which may cause malfunction. Will increase and the impact will be great.

  Recently, as shown in FIG. 6, an actuator 17 such as an LED or a motor is mounted on a wireless tag, and not only transmits an ID but also operates the actuator to transmit the position of the wireless tag through one of the five human senses. Tags have been developed. However, when the actuator 17 and the activation of the MCU 14 are synchronized with each other, the actuator 17 consumes electric power, so that the start-up of the power supply 12 is further delayed and the possibility of causing the malfunction of the MCU 14 is further increased. End up.

  Accordingly, an object of the present invention is to provide an active wireless tag that is small and lightweight, and that can be stably started even when the power supply capacity of the MCU is small.

  In order to solve the above-described problems, an active wireless tag according to the present invention is an active wireless tag including an MCU and a power source. When the power of the active wireless tag is turned on, the power supply voltage of the MCU is the operating voltage of the MCU. And a means for inputting a reset signal of the MCU after a predetermined time elapses.

  Further, as means for inputting the reset signal of the MCU after the fixed time has elapsed, a voltage detector that detects the arrival of the power supply voltage of the MCU to the reference voltage and outputs a voltage arrival signal; and the voltage arrival signal A delay circuit having a timer function may be provided which includes an oscillation circuit and a counter circuit for delaying the signal by a predetermined time and outputting it as a reset signal.

  It is desirable that the delay circuit is integrated in the voltage detector.

  The delay time of the delay circuit is preferably set to 2 μs or more and 200 ms or less.

  Moreover, it has at least 1 or more of LED, a motor, or a sounder as an actuator, The said power supply may be comprised with the lithium ion battery.

  As described above, according to the present invention, even if the MCU is reset by the power-on reset function, the power supply voltage of the MCU subsequently rises to a certain reference voltage that is equal to or higher than the lower limit value of the MCU operating voltage, and a certain time has elapsed. However, when the activation of other blocks such as the communication unit and the actuator is completed and there is no possibility of malfunction, the MCU can be stably activated by inputting and resetting the MCU reset signal again.

  More specifically, the delay of the predetermined time can be obtained by a voltage detector for detecting the arrival of the power supply voltage to the reference voltage and a delay circuit using an oscillation circuit and a counter timer. Although a delay circuit can be configured using resistors and capacitors, it is necessary to increase the capacity of the capacitor in order to increase the delay time, and the size of the capacitor will increase, making it compact and lightweight that can be mounted on goods, etc. It is difficult to realize a simple wireless tag. In the present invention, a voltage detector having a built-in delay circuit using an oscillation circuit and a counter timer can be used, and a more compact wireless tag can be realized.

  As described above, regardless of the presence of the MCU power-on reset function, it is possible to stably start without malfunction even when realizing an active type wireless tag equipped with an LED, motor, or sounder as an actuator in the wireless tag. Thus, a small active type wireless tag capable of performing

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing an embodiment of an active wireless tag according to the present invention. As shown in FIG. 1, the active wireless tag according to the present embodiment includes a communication unit including an MCU 4, a power source including a lithium ion battery 1 and a DC-DC converter 2, a wireless unit 5, and an antenna 6. It includes an actuator 7 such as an LED or a motor. When the power is turned on, the power supply voltage of the MCU 4 rises to a certain reference voltage that is equal to or higher than the minimum operating voltage of the MCU 4, and a reset signal for the MCU 4 is input after a certain time has passed. A voltage detector 3 and a delay circuit 13 are provided as means for performing this.

  FIG. 2 is a diagram showing the relationship between the rise time change of the power supply voltage of the MCU 4 of the active wireless tag of this embodiment and the generation of the reset signal. As shown in FIG. 2, the power supply voltage rises to the reference voltage. And a voltage detector 3 for detecting the arrival of the power supply voltage of the MCU 4 to the reference voltage and outputting a voltage arrival signal in order to generate a reset signal of the MCU 4 after a predetermined time of 2 μs to 200 ms elapses. The delay circuit 13 includes a oscillating circuit and a counter circuit for delaying the voltage arrival signal by a predetermined time and outputting the delayed signal as a reset signal and having a timer function.

  By delaying the reset operation by the delay circuit 13 until the power supply voltage rises to the reference voltage and the activation of the communication unit and the actuator ends and stabilizes, an active wireless tag that can be activated without malfunction can be realized. At this time, the reference voltage value is related to the size of the MCU 4, but when the MCU 4 is a 16-bit MCU and a bypass capacitor of about 10 μF is installed, a voltage value that is about 20% larger than the minimum operating voltage is optimal. The delay time is related to the power supply capacity, but when the MCU4 is a 16-bit MCU and a bypass capacitor of about 10μF is installed, the effect of delaying the reset signal can be confirmed even with a minimum delay time of about 2μs. Although the time is limited by the circuit operation speed of the MCU and others, it is considered that about 200 ms is appropriate in consideration of feasibility and response time.

  FIG. 3 is a configuration diagram showing an example of a configuration of a communication system using the active wireless tag according to the present embodiment. Communication is performed between the reader / writer 9 connected to the computer 10 and the active wireless tag 8. Done.

  As shown in FIG. 1, the MCU 4 stores the ID and digital data of the active wireless tag, controls the wireless unit 5 during communication, and controls the actuator 7. The wireless unit 5 wirelessly transmits a digital data signal from the MCU 4 to the reader / writer 9 (FIG. 3) via the antenna 6. Further, the lithium ion battery 1 and the DC-DC converter 2 that constitute the power supply unit supply power for driving the voltage detector 3, the delay circuit 13, the MCU 4, the radio unit 5, and the actuator 7.

  FIG. 4 is a perspective view showing an example of the configuration of the active wireless tag according to the present embodiment. As shown in FIG. 4, the external dimensions of this configuration are a general card size having a width dimension a of 44 mm, a depth dimension b of 65 mm, a height dimension c of 11 mm, a width dimension of 54 mm, and a depth dimension of 85.5 mm. Smaller. In this configuration, a voltage detector incorporating a delay circuit 13 is used as the voltage detector 3. Specifically, an S-801 series IC manufactured by Seiko Instruments Inc. can be used. In this case, the delay time is set to 200 ms. FIG. 5 shows a detailed circuit diagram thereof. A power supply from the DC-DC converter 2 is connected to the VDD terminal, and a delayed reset signal is obtained from the OUT terminal. That is, the voltage arrival signal input to the delay circuit in the circuit diagram of FIG. 5 is delayed by the delay circuit, processed, and output from the OUT terminal. The minimum operating voltage of the MCU 4 is about 1.8V, and the reference voltage is set to about 2.1 to 2.3V. In this configuration, as the lithium ion battery 1, a small lithium ion battery having a power supply capacity as small as 300 mAh was used. Here, since the lithium ion battery is used, this active wireless tag is rechargeable.

  Moreover, LED11 (FIG. 4) is connected to MCU4 as an actuator, and is controlled. In this case, since the power supply capacity is small, the LED 11 also consumes power when the power is turned on, so the rise of the power supply is delayed. However, as described above, the voltage detector with a built-in delay circuit is connected to the MCU 4 and reset again in a stable state. Therefore, no malfunction occurs.

  As described above, the active wireless tag according to the present invention provides an active wireless tag that is small and lightweight, and that can be stably activated even when the power supply capacity is small.

  Needless to say, the present invention is not limited to the above-described embodiments and configuration examples. For example, the same function can be obtained as means for inputting the MCU reset signal after the MCU power supply voltage rises to a certain reference voltage equal to or higher than the lower limit value of the MCU operating voltage and after a certain time has passed. If so, a circuit other than the circuit of the above configuration example can be used, and the value of the reference voltage may be selected in accordance with the capacity of the communication unit, actuator, power supply unit, and the like.

1 is a block diagram showing an embodiment of an active wireless tag according to the present invention. The figure which shows the relationship between the rise time change of the power supply voltage of MCU of the active type | mold radio tag of this Embodiment, and generation | occurrence | production of a reset signal. The block diagram which shows an example of the structure of the communication system using the active type | mold radio | wireless tag of this Embodiment. FIG. 11 is a perspective view illustrating an example of a structure of an active wireless tag of this embodiment. The detailed circuit diagram of the voltage detector with a built-in delay circuit used for this structure. The basic block block diagram of the conventional active type | mold radio | wireless tag. The figure which shows the difference in the rise time of the power supply voltage by the difference in power supply capacity.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 DC-DC converter 3 Voltage detector 13 Delay circuit 4, 14 MCU
5 Radio section 6 Antenna 7, 17 Actuator 8 Active type wireless tag 9 Reader / writer 10 Computer 11 LED
12 power supply unit 15 communication unit

Claims (5)

  In an active type wireless tag equipped with an MCU (microcontroller unit) and a power source, when the power is turned on, the power source voltage of the MCU rises to a certain reference voltage that is equal to or higher than the lower limit value of the operating voltage of the MCU, and a certain time has passed. An active type radio tag comprising means for inputting a reset signal of the MCU after the operation.   As means for inputting the reset signal of the MCU after the fixed time has elapsed, a voltage detector that detects the arrival of the power supply voltage of the MCU to the reference voltage and outputs a voltage arrival signal, and the voltage arrival signal is constant 2. The active wireless tag according to claim 1, further comprising a delay circuit configured by an oscillation circuit and a counter circuit for delaying time and outputting as a reset signal and having a timer function.   3. The active wireless tag according to claim 2, wherein the delay circuit is integrated in the voltage detector.   4. The active wireless tag according to claim 2, wherein the delay time of the delay circuit is set to 2 [mu] s or more and 200 ms or less.   5. The active wireless tag according to claim 1, wherein the actuator includes at least one of an LED, a motor, and a sounder as an actuator, and the power source is configured by a lithium ion battery.

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