JPH071314B2 - Rear member detection device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a pillar such as a furring strip, a stud, a field rim, etc., which is behind a wall material or a ceiling material made of plywood or gypsum board and to which the wall material or the ceiling material is attached. The present invention relates to a back member detection device that detects a water pipe, a conduit pipe, or the like arranged behind a wall or a ceiling.

[Background Art] Generally, when a wall or ceiling is formed by wall materials or ceiling materials such as plywood or gypsum board, and when attaching a clock or forehead to the wall or attaching lighting to the ceiling or wall, It is necessary to find the pillars (studs, furrows, rims, etc.) provided on the back of the wall material to attach the wall material and ceiling material, and attach nails and hooks to the pillars. When installing, it is necessary to make holes by avoiding water pipes and conduits buried in walls and ceilings. However, since the surface of wall materials and ceiling materials is generally surface-finished by applying a decorative sheet or painting, it is not possible to visually find the positions of back members such as stanchions, water pipes and electric conduits. Have difficulty.

Therefore, conventionally, a method of hitting the surface of a wall material or a ceiling material with a hammer or the like and detecting the position of the backing member by utilizing the fact that the generated sound changes depending on the presence or absence of the backing member has been generally used. However, since a gypsum board or the like has little change in sound due to the presence or absence of the back member, it is difficult for a skilled person to detect the back member by this method.

In order to solve such a problem, as shown in FIG. 4, an electrode plate 1 is provided as a sensor unit, and a change in the dielectric constant around the electrode plate 1 is detected to detect a rear member of a wall or a ceiling. A device designed to detect is considered. This device detects the surrounding capacitance by the electrode plate 1 and detects the resistance.
A time constant circuit is formed with R ₁ , R ₂ and variable resistance VR ₁ , and a pair of monostable multivibrator 1 is formed based on this time constant.
1 and 12 are operated, and after the difference between the pulse widths of the output pulses of both monostable multivibrators 11 and 12 is detected by the time difference detection circuit 13, the output of the time difference detection circuit 13 is integrated by the integration circuit 14 and the integration circuit 14 When the output level of 1 reaches a predetermined value, the switching circuit 15 is operated to turn on the light emitting diode LED which is the notification means. By the way, since the surrounding electrostatic capacitance detected by the electrode plate 1 changes depending on the material and thickness of the wall or the like, in the device having the above configuration, the maximum sensitivity can be used according to the usage environment.
A reference value setting circuit 16 for automatically setting a reference value for operation is provided. That is, the reference value setting circuit 16 changes the time constant according to the use environment by applying a bias voltage to the time constant circuit of the monostable multivibrator 12, and at the time when the maximum sensitivity is set according to the use environment. It is configured to hold the bias voltage. Therefore, the reference value is set by the bias voltage, and the bias voltage is obtained as the terminal voltage of the capacitor C. That is, when the power is turned on, the switch element S is brought into the conductive state to charge the capacitor C, and when it is detected that the maximum sensitivity is set, the switch element S is brought into the non-conductive state and the charging of the capacitor C is stopped. The terminal voltage of the capacitor C is applied to the connection point of the resistors R ₁ and R ₂ via the voltage follower Vf. Here, CMOS is conventionally used as the switch element S and the voltage follower Vf because of its small size and low cost, and has the following problems. That is, CMOS has variations in threshold, and when the conduction time of the switch element S is set by the time constant circuit of the capacitor C and the resistor R ₃ as shown in FIG. 4, as shown in FIG. , The maximum value of the terminal voltage of the capacitor C varies, and the adjustment range of the output voltage of the voltage follower Vf varies. Therefore, in order to keep the product specifications constant, it is necessary to adjust to the narrowest adjustment range of the bias voltage that sets the initial state, and as a result, there is a problem that the range of wall thickness applicable to the device is reduced. It was

[Object of the Invention] The present invention has been made in view of the above points, and an object thereof is to charge a capacitor once instead of setting the terminal voltage of the capacitor in the process of charging the capacitor. It is an object of the present invention to provide a backing member detection device in which the terminal voltage of the capacitor is set in the process of discharging afterwards, so that the setting range of the reference value can be made large.

DISCLOSURE OF THE INVENTION (Structure) In the back member detection device according to the present invention, a sensor unit that converts a change in the surrounding dielectric constant into an electric signal, and a strut when the output of the sensor unit reaches a preset reference value. It is provided with a detection means that determines that it exists and obtains a detection output, and a reference value setting circuit that sets the above-mentioned reference value according to the surrounding environment. After setting the reference value, the capacitor is charged when the power is turned on, and the reference value is set so that the detection output can be obtained regardless of the presence or absence of the support post, and then the switch element provided in the discharge circuit that discharges the capacitor is turned on. In this condition, the reference value is maintained by stopping the discharge of the capacitor by setting the switch element to the non-conducting state immediately after the capacitor is discharged and no detection output is obtained. It is those which comprising a, is obtained by preventing by performing setting of the reference value in the discharge process of the capacitor, the variation in the setting range of the reference values due to variations in the threshold, etc. other components.

(Example) As shown in FIG. 1, one main electrode plate 1a and one main electrode plate 1a
An electrode plate 1 provided with a pair of sub-electrode plates 1b and 1c arranged on both sides of is used as a sensor unit. Main electrode plate 1a is variable resistance VR
_It is connected to one end of 1 to form a first time constant circuit, and both sub-electrode plates 1b and 1c are connected to each other and a power source
Variable resistor VR _{1 to be} divided and variable resistor V of resistors R ₁ and R ₂
The second time constant circuit is formed by being connected to the connection point between R ₁ and the resistor R ₁ . Each time constant circuit sets each time constant of the pair of monostable multivibrators 11 and 12, respectively, and the inverting output of one monostable multivibrator 11 and the non-inverting output of the other monostable multivibrator 12 are set. Is input to the time difference detection circuit 13. The time difference detection circuit 13 outputs an output pulse corresponding to a period in which the input levels from both monostable multivibrators 11 and 12 are both "L", and this output pulse is integrated by the integrating circuit 14. When the output level of the integrating circuit 14 reaches the reference level set by the switching circuit 15, the switching circuit 15 outputs a detection output to turn on the light emitting diodes LED ₁ and LED ₂ which are the notification means. Here, both light emitting diodes LED ₁ , LED ₂
Blinks according to the input level to the switching circuit 15. As described above, the monostable multivibrator 11, 12 including the time constant circuit, the time difference detection circuit 13, the integration circuit 14,
The switching circuit 15 constitutes a detecting means.

The switching circuit 15 includes a transistor Q for inverting and amplifying the output of the integration circuit 14, a pair of comparators 21a and 21b,
The resistors R _{3 to} R ₅ are provided. Further, the output resistance R ₆ is connected to the collector of the transistor Q, and the variable resistance VR ₂ for setting the amplification factor is connected to the emitter of the transistor Q. Both comparators 21a, is between the output ends of 21b are inserted in series circuit of a resistor R ₇ and the light emitting diode LED ₁ is emitting a resistor R ₈ is between the negative end of the output terminal and the power supply of one of the comparators 21b A series circuit with diode LED ₂ is inserted.

The detection operation is performed as shown in the right half of FIG. That is, as shown in FIGS. 2A and 2B, the time constant is set by the electrostatic capacity detected by the electrode plate 1, the variable resistance VR ₁ and the resistances R ₂ and R _3, and FIG. c)
As shown in (d), a pulse having a pulse width corresponding to the time constant is obtained at the output of each monostable multivibrator 11, 12. The outputs of both monostable multivibrators 11 and 12 are input to the time difference detection circuit 13 and correspond to the output pulse width difference of both monostable multivibrators 11 and 12 as shown in FIG. , Both monostable multivibrator 1
A pulse corresponding to the pulse width during the period when both the output levels of 1 and 12 are "L" is obtained. The output of the time difference detection circuit 13 is integrated by the integration circuit 14, and an output whose level increases according to the output pulse width of the time difference detection circuit 13 is obtained as the output of the integration circuit 14. Therefore, the output level of the transistor Q provided in the switching circuit 15 decreases as the output pulse width of the time difference detection circuit 13 increases, as shown in FIG. 2 (f). During the detection operation, the comparators 21a, 21b of the switching circuit 15 are
Is set to a constant value, and when the output level of the transistor Q becomes less than the set value, the output level of one comparator 21a becomes "H" as shown in FIG. When LED ₁ lights up and the output level further decreases, the output level of the other comparator 21b becomes "H" as shown in FIG. 2 (h), and the light emitting diode LED
₂ is lit up. However, when there is a back member on the wall or ceiling, the capacitance detected by the main electrode 1a increases and the time constant of the monostable multivibrator 11 increases, so the output pulse width of the time difference detection circuit 13 is increased. Is increased, and as a result, the light emitting diode LED ₁ is turned on when the column is approached to some extent. When the center of the rear member is further approached, the light emitting diode LED ₁ is turned off and the light emitting diode LED ₂ is turned on.

By the way, a bias voltage from the reference value setting circuit 16 is applied to the connection point of the resistors R ₁ and R ₂ , and the time constant of the monostable multivibrator 12 is variable by this bias voltage. The reference value setting circuit 16 includes diodes D _{1 to} D ₃ , capacitors C, C ₁ and C ₂ , resistors R _{9 to} R ₁₄ , a pair of CMOS switch elements S ₁ and S ₂ , and a voltage follower composed of CMOS.
It is composed of Vf, an inverter I, and a NOR circuit NOR, and the switch elements S ₁ and S ₂ and the voltage follower Vf are composed of one integrated circuit. The bias voltage is applied by taking out the terminal voltage of the capacitor C by the voltage follower Vf, and the voltage follower Vf is configured to invert the terminal voltage of the capacitor C. That is, the higher the terminal voltage of the capacitor C, the lower the output voltage of the voltage follower Vf. This reference value setting circuit 16 changes the time constant of the monostable multivibrator 12 by changing the terminal voltage of the capacitor C when the power is turned on, and thereby the minimum value of the electrostatic capacitance that can be detected by the main electrode 1a. Is automatically set according to the usage environment.

Next, the operation of the reference value setting circuit 16 will be described with reference to the left half of FIG. First, when the power is turned on, the capacitor C ₁ is charged through the resistor R _3, and the switch element S ₁ is in the conductive state while the terminal voltage of the capacitor C ₁ is low. Therefore, the capacitor C is connected to the resistors R ₃ , R ₉ , R ₁₀ , and the diode D ₁ etc. are charged. The charging time constant for the capacitor C is set sufficiently short, and the charging time constant for the capacitor C ₁ is set longer than that. Further, the capacitor C ₂ is charged at the same time when the power is turned on via the resistor R ₁₄ , and also via the resistors R ₅ , R ₆ , R ₁₂ and the diodes D ₂ , D _{3, so} that one input level of the NOR circuit NOR is charged. Has been "L" for a while since the power was turned on. Further, since the input level of the non-inverting input terminal of the comparator 21a is "L", the output level of the comparator 21a is "L" and the output level of the NOR circuit NOR is as shown in FIG. 2 (i). , "H". Further, as shown in FIG. 2 (j), the output level of the inverter I is "L".
Therefore, the non-inverting input terminal of the comparator 21b is "L".
Then, as shown in FIG. 2 (h), the output level of the comparator 21b becomes "H", and the light emitting diode LED ₂ lights up. By the way, at this time, the switch element S ₂ is conducting, and the capacitor C is discharged through the resistor R ₁₁ . That is,
Charging and discharging are performed at the same time when the power is turned on,
Since the discharge time constant is set sufficiently larger than the charge time constant, the terminal voltage of the capacitor C is a switch element.
It quickly rises while S ₁ is conducting. When the terminal voltage of the capacitor C ₁ rises and the switch element S ₁ becomes non-conductive, the capacitor C only discharges as shown in FIG. 2 (k), and accordingly, the resistors R ₁ and R ₂ are discharged. The potential at the connection point of is gradually increased as shown in FIG. That is, as shown in FIG. 2 (b), the time constant of the time constant circuit connected to the monostable multivibrator 12 gradually decreases, and as shown in FIG. 2 (d), the monostable multivibrator 12 The output pulse width of is gradually reduced. When the output pulse widths of both monostable multivibrators 11 and 12 become substantially equal in this way, as shown in FIG. 2 (e), a minute pulse is obtained from the time difference detection circuit 13 which has been non-output until then.
The output level of the integrating circuit 14 rises slightly and the collector potential of the transistor Q falls slightly as shown in FIG. 2 (f).
At this point, as shown in FIG. 2 (g), the output level of the comparator 21a becomes “H” and the input level of the NOR circuit NOR on the resistor R ₁₃ side becomes “H”. NOR circuit output level of the NOR becomes "L" as the output level of the inverter I becomes the "H", the switch element S ₂ becomes nonconductive, the discharge of the capacitor C is stopped. Further, the light emitting diode LED ₂ is turned off as shown in FIG. The moment the comparator 21a, since the reference voltage at the non-inverting input of the 21b becomes a resistor R _3, divided by the value of the supply voltage R _9, both comparators 21a, the voltage applied to the non-inverting input of 21b downward Both LED's LED ₁ and LED ₂ are turned off. That is, after the light emitting diode LED ₂ is turned off, the light emitting diode LED ₁ is momentarily turned on and then immediately turned off. After that, the terminal voltage of the capacitor C is kept constant, and the initial value of the bias voltage to the time constant circuit is set. By setting this bias voltage, the time difference detection circuit 13 is in a state where an output pulse with an extremely small width is obtained, so that a wide pulse can be obtained from the time difference detection circuit 13 as soon as the back member is detected, and high sensitivity is obtained. The detection operation can be performed in.

As described above, since the bias voltage is set in the discharging process after the capacitor C is once charged, as shown in FIG. 3, the CMOS of the switch elements S ₁ and S ₂ and the voltage follower Vf which constitutes the voltage follower Vf is set. Even if the characteristics vary, the voltage adjustment range is not affected, and as a result, the usable wall thickness range does not vary from product to product.

[Advantages of the Invention] As described above, the present invention determines that a sensor unit that converts a change in the surrounding dielectric constant into an electric signal and that a pillar is present when the output of the sensor unit reaches a preset reference value. Detecting means for obtaining a detection output, and a reference value setting circuit for setting the reference value according to the surrounding environment, the reference value setting circuit has a capacitor and the reference value in response to the terminal voltage of the capacitor. After setting, set the reference value to a state where the capacitor is charged when the power is turned on and the detection output is obtained regardless of the presence or absence of the support, then the switch element provided in the discharge circuit that discharges the capacitor is set to the conductive state to discharge the capacitor. Immediately after the detection output is no longer obtained, the switch element is set to the non-conducting state to stop the discharge of the capacitor and the reference value is held. Therefore, the reference value is set in the process of discharging the capacitor, so that there is an advantage that variation in the setting range of the reference value due to variation in thresholds of other components can be prevented. As a result, the performance of each product can be made constant while increasing the range of applicable wall thickness.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a time chart showing signals of corresponding parts in FIG.
FIG. 3 is an operation explanatory view of the main part of the above, FIG. 4 is a block diagram showing a conventional example, and FIG. 5 is an operation explanatory view of the same. 1 is an electrode plate, 11 and 12 are monostable multivibrators, 13 is a time difference detection circuit, 14 is an integration circuit, 15 is a switching circuit, 16 is a reference value setting circuit, C is a capacitor, S ₁ and S ₂ are switching elements. is there.

Claims (1)

[Claims] 1. A sensor unit for converting a change in the dielectric constant of the surroundings into an electric signal, and a detection unit for obtaining a detection output by determining that a support is present when the output of the sensor unit reaches a preset reference value. , A reference value setting circuit that sets the reference value according to the surrounding environment.The reference value setting circuit has a capacitor and sets the reference value in response to the terminal voltage of the capacitor. After setting the reference value to a state where the detection output can be obtained regardless of the presence or absence of the support after charging, the switch element provided in the discharge circuit that discharges the capacitor is turned on to discharge the capacitor and the detection output cannot be obtained. A back member detection device, characterized in that it is set to hold the reference value by stopping the discharge of the capacitor by setting the switch element to the non-conducting state immediately after that.