JP2000137887A - Wireless sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the interference of radio waves when data is transmitted from plural wireless sensors. SOLUTION: The plural series circuits of resistors and switches are connected to a modulation part 13 in parallel. Resistors r1, r2 and r3 are those for deciding the frequency dividing ratio of a frequency divider and the switches SW1, SW2 and SW3 are changed over by a manual operation. Thus, a transmission frequency can be switched by a manual operation by changing over the switches SW1, SW2 and SW3. Consequently, the mutual interference of radio waves transmitted from wireless sensors can be avoided by suitably deciding the transmission frequencies of the respective wireless sensors at the time of installing the wireless sensors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wireless sensor.

[0002]

2. Description of the Related Art As a security system using a wireless sensor, a configuration as shown in FIG. 3 can be considered. FIG. 3 is a diagram showing a configuration example of a security system using a wireless sensor constructed in a certain two-story building, where 1 indicates a wireless sensor and 2 indicates a receiver.

[0003] On the first and second floors of the building, a predetermined number of wireless sensors 1 are respectively installed at appropriate positions. In FIG. 3, three wireless sensors are installed on the first floor and two wireless sensors are installed on the second floor. A receiver 2 is installed on each floor. The receiver 2 installed on the first floor is 1
It is for receiving radio waves transmitted wirelessly from the wireless sensor 1 installed on the floor, and the receiver 2 installed on the second floor is wirelessly transmitted from the wireless sensor 1 installed on the second floor. It is for receiving radio waves.

A security system using such a wireless sensor is well known, but is briefly described as follows. Although there are various sensors as the wireless sensor 1, it is assumed that all the wireless sensors 1 are wireless hot-wire sensors.

[0005] The wireless sensor 1 is always operating,
When a change in the heat ray is detected, information indicating that the change in the heat ray is detected (hereinafter, referred to as detection information) is wirelessly transmitted. The receiver 2 can be set to the alert state / release state. If the release state is set, the receiver 2 ignores the detection information wirelessly transmitted from the wireless sensor 1 but ignores the detection information. Is set, when the detection information wirelessly transmitted from the wireless sensor 1 is received, the information indicating the occurrence of the abnormality is reported to the center device of the security company via the telephone line. In the configuration shown in FIG. 3, the notification to the center device may be made from the receiver 2 on each floor via a telephone line, respectively, and the signal from the receiver 2 on each floor is temporarily sent to the notification device ( (Not shown in FIG. 3) and may be notified to the center device by the notification device.

[0006]

By the way, the transmission output of the conventional wireless sensor is made as large as possible. Under the current method, the transmission power allowed for the wireless sensor is 10 mW at the maximum, so that the transmission power of the conventional wireless sensor is usually set to 10 mW. The reason why the transmission output is made to be the allowable limit is that the radio wave must not reach the receiver 2 from the wireless sensor 1. Conventionally, the transmission output of the wireless sensor is fixed.

Further, in the configuration shown in FIG. 3, the transmission frequencies of the wireless sensors 1 are usually all the same.

In the configuration shown in FIG. 3, for example, there is a case where a certain wireless sensor 1 installed on the second floor and a certain wireless sensor 1 installed on the first floor detect a change in the heat ray almost simultaneously. In this case, detection information is wirelessly transmitted from these wireless sensors 1 almost at the same time. However, as described above, conventionally, the transmission frequency is the same, and the transmission output is both maximized. Radio waves wirelessly transmitted from the two wireless sensors interfere with each other, and there is a possibility that the detection information transmitted from the wireless sensor 1 cannot be normally received by the receiver 2 on the first floor or the receiver 2 on the second floor. .

SUMMARY OF THE INVENTION The present invention has been made in order to prevent the above-described situation from occurring. Even when a plurality of wireless sensors transmit detection information by radio at almost the same time, detection from each wireless sensor is performed. It is an object of the present invention to provide a wireless sensor capable of enabling information to be normally received by a corresponding receiver.

[0010]

To achieve the above object, a wireless sensor according to the first aspect is characterized in that the transmission output can be manually switched. A wireless sensor according to a second aspect is characterized in that the transmission frequency can be manually switched.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In the following, a case where the present invention is applied to a wireless hot-wire sensor will be described. FIG. 1 is a diagram showing a first embodiment in which the present invention is applied to a wireless hot-wire sensor. In the drawing, 10 is a sensor head, 11 is a signal processing unit, 12 is a CPU, 13 is a modulation unit, and 14 is An amplifier, 15 is a filter, 16 is a final stage amplifier, 17 is a battery as a power supply of the wireless hot-wire sensor, 18 is a switch, 19 is an antenna, S1, S1, S
2 indicates a switch, and R1 and R2 indicate resistors.

In FIG. 1, the sensor head 10, the signal processing unit 11, and the CPU 12 are always supplied with power from a battery 17. The switch 18 is always open, and is closed by the CPU 12 only when wirelessly transmitting detection information. Therefore, the modulator 13, the amplifier 14, the filter 1
5. Power is supplied from the battery 17 to the amplifier 16 only when the detection information is wirelessly transmitted.

[0013] A plurality of series circuits of resistors and switches are connected in parallel to the amplifier 16, which is the final stage amplifier. In the figure, a series circuit of a resistor R1 and a switch S1 and a series circuit of a resistor R2 and a switch S2 are connected in parallel. Of course, three or more series circuits of the resistor and the switch may be connected in parallel. This resistance R
1 and R2 are resistors for determining the transmission output, for example, the load resistance of the amplifier 16. Also, the switches S1,
At least one of S2 is closed. In the figure, switch S2 is closed and switch S1 is open. These switches S1 and S2 are manually switched.

The sensor head 10 comprises a pyroelectric element as a heat ray detecting element, a reflecting mirror for defining a warning zone, and the like. The output signal from the pyroelectric element is subjected to predetermined processing such as amplification and A / D conversion in the signal processing unit 11 and is input to the CPU 12.

The CPU 12 takes in the output signal from the signal processing unit 11, compares it with a predetermined threshold value,
If the acquired output signal of the signal processing unit 11 is equal to or greater than the threshold value, it is determined that the heat ray has changed, that is, the movement of a person has been detected, the switch 18 is closed, and the data is transmitted to the modulation unit 13. send. This data is detection information.
Then, the data of the detection information is modulated by the modulation unit 13,
Amplified by the amplifier 14, band-limited by the filter 15,
The signal is amplified by the amplifier 16 and wirelessly transmitted from the antenna 19. The transmission output at this time corresponds to the resistance value of the resistor R2 in the figure. If the switch S1 is closed and the switch S2 is open, the transmission output is determined according to the resistance value of the resistor R1, and if both the switches S1 and S2 are closed, the transmission output is determined. It is determined by the combined resistance value of R2.

As described above, in the wireless hot-wire sensor shown in FIG. 1, by switching the switches S1 and S2,
The transmission output can be switched manually.

Next, the usage of the wireless sensor shown in FIG. 1 will be described. In the security system having the configuration shown in FIG. 3, it is assumed that the wireless hot-wire sensor shown in FIG.

In this case, first, the wireless sensors 1 are installed on each floor. At this time, the switches S1 and S2 are set so that the transmission output of each wireless sensor 1 is maximized. Then, it is checked whether or not the above-mentioned radio interference occurs due to the movement of a person after the installation. If the radio interference occurs, the transmission output of the wireless sensor 1 is switched by switching a switch connected to the amplifier 16. This can avoid radio wave interference.

Next, referring to FIG. 2, it is a diagram showing a second embodiment in which the present invention is applied to a wireless hot-wire sensor, in which SW1, SW2, and SW3 are switches, r
1, r2 and r3 indicate resistances. Note that the same components as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted.

In FIG. 2, the transmission output is fixed. A plurality of series circuits of resistors and switches are connected in parallel to the modulator 13. In the figure, the resistor r1 and the switch SW1
, A series circuit of the resistor r2 and the switch SW2, and a series circuit of the resistor r3 and the switch SW3 are connected in parallel. Of course, four or more series circuits of resistors and switches may be connected in parallel.

The modulating section 13 includes at least an oscillator for generating a reference frequency, a frequency divider for dividing the output of the oscillator, and a modulator for modulating data to be transmitted by the output of the frequency divider. Are the resistances r1, r2,
r3 is a resistor for determining the frequency division ratio of the frequency divider. At least one of the switches SW1, SW2, and SW3 is closed. In the figure, the switch SW3 is closed and the switches SW1 and SW2 are open. These switches SW1, SW2, and SW3 are manually switched.

As described above, in the wireless hot-wire sensor shown in FIG. 2, the transmission frequency can be manually switched by switching the switches r1, r2, and r3. Therefore, when the wireless hot-wire sensor shown in FIG. 2 is used as the wireless sensor 1 in the security system having the configuration shown in FIG.
By appropriately setting the transmission frequency, it is possible to avoid radio wave interference as described above.

Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above-described embodiment, the wireless hot-wire sensor has been described. However, the present invention is not limited to the wireless hot-wire sensor, and can be applied to other wireless sensors.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a first embodiment of a wireless sensor according to the present invention, and is a diagram illustrating a configuration example when the present invention is applied to a wireless hot-wire sensor.

FIG. 2 is a diagram illustrating a second embodiment of the wireless sensor according to the present invention, and is a diagram illustrating a configuration example when the present invention is applied to a wireless hot-wire sensor.

FIG. 3 is a diagram illustrating a configuration example of a security system using a wireless sensor and explaining a problem to be solved by the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wireless sensor, 2 ... Receiver, 10 ... Sensor head, 11 ... Signal processing part, 12 ... CPU, 13 ... Modulation part,
14 ... Amplifier, 15 ... Filter, 16 ... Final stage amplifier, 17 ... Battery as a power source of the wireless hot-wire sensor, 18 ... Switch, 19 ... Antenna.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5C087 BB20 BB39 BB75 DD05 DD23 EE08 EE10 FF01 FF04 FF13 FF17 GG03 GG08 GG11 GG31 GG51 GG57

Claims (2)

[Claims] 1. A wireless sensor wherein the transmission output is manually switchable. 2. The wireless sensor according to claim 1, wherein the transmission frequency is manually switchable.