KR100395410B1 - Automatic shield device of noxious waves of electric mat - Google Patents

Abstract

The present invention relates to an automatic shielding device for harmful electromagnetic waves using a shield board inherent in an electric mat. When using an electric mat, a power distribution method or a power plug such as a one-wire grounding zone or a neutral grounding zone may be replaced. Without the need for hot wires, neutral wires or ground or virtual grounds are found and automatically connected to the shield (shield board) to block harmful electromagnetic waves.

Looking at the configuration, it displays a clock signal for supplying a clock signal of AC 60Hz to the clock terminal of the binary counter, a switch for supplying or blocking the clock signal to a binary counter, and the operation state of the binary counter The display unit, a binary counter for outputting a status signal while ring counting according to the input of the clock signal, and a ground counter cannot be found if the outputs of both ends of the binary counter are all 'H'. A driver for amplifying the counter, a driver for amplifying the output signal of the binary counter, and a ground source of one of AC1 power, AC2 power, ground wire, or virtual ground, depending on the output state of the binary counter. It is to find the ground (virtual ground) of the shield automatically by configuring the switch to connect to the shield to find.

Description

Automatic shield device of noxious waves of electric mat

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an automatic shielding device for harmful electromagnetic waves using a shield board built into an electric mat. Highly reliable to block harmful electromagnetic waves by automatically connecting to the shield board by finding neutral wires, ground wires or virtual grounds, not hot wires, without the need to change the power plug. It is to provide an automatic electromagnetic shielding device.

In general, commercial AC power supplies to homes or business offices are provided with a separate ground line in addition to the neutral line and hot line to protect the human body from the risk of electric shock.

On the other hand, electric and electronic products that use electric energy generate electric and magnetic fields by electric energy, and the electric field emits harmful electromagnetic waves. It is doing harm.

In particular, in the case of an electric mat for heating using a heat source of electric energy, the user lies on or sits thereon, and the weight of the user presses the heating plate, so that the heating plate and the human body are in close proximity. Therefore, the electric field and a large amount of harmful electromagnetic waves are directly induced to the human body to have a very harmful action.

As a way of suppressing the harmful electromagnetic waves, a material that can absorb or neutralize the harmful electromagnetic waves emitted from the heat transfer plate, for example, jade, rock, and charcoal, is used when manufacturing the electric mat, but the effect is less than expected. It is insignificant.

Therefore, a soft shielding plate made of a conductor, such as aluminum foil or metal foil, or a sheet or metal wire tightly woven shielding plate is installed on the heat transfer plate of the electric mat, and then the power outlet and power plug are installed. Shielding of electric fields and harmful electromagnetic waves is achieved by configuring a circuit to be connected to the ground wire provided through the circuit.

However, when a ground wire is provided through a power outlet and a power plug, the shielding plate and the ground wire are connected to each other, thereby effectively blocking harmful electromagnetic waves, but grounding the power outlet, the power plug, or the power outlet and the power plug respectively. In case of no construction or not connected to ground wire, the shielding circuit is cut off, so it is impossible to block harmful electromagnetic waves.

As above, the circuit is constructed so that the neutral wire and the shield plate connected to the ground and ground are connected in case the ground wire (ground wire) fails to serve as a ground or the grounding work is not performed, but the neutral wire of the power outlet or power plug Not only are they clearly distinguishable, but even if they are classified, the neutral and hot wires are often replaced by wires.

In this case, it is inconvenient to change the direction of the power plug, so it is not accurate and safe to use. If the hot wire is connected to the shielding plate, there is a risk of electric shock, fire, or failure of the mat.

In addition, the neutral wire cannot be found due to a circuit breakdown or an electric field generated from a heating plate while the temperature controller is placed on an electric mat, or an electric field induced by a metal workbench or a metal rim of a desk. In this case, the neutral wire is found, but the neutral wire is misinterpreted as being found due to the interference or influence of the wrong voltage. Therefore, the automatic switching is not performed. Therefore, the user is exposed to harmful electromagnetic waves.

In addition, by installing a probe terminal that can be touched by a finger, etc. in the temperature controller, when the human body is touched, the neutral wire and the shield plate are directly connected by comparing the connection between the neutral wire and the shield plate or the hot wire and the shield plate due to the change in capacitance. If there is a check device configured to make the lamp turn on, there is a problem that the user should check the lighting state of the lamp by directly touching the transducer by hand whenever the user plugs the power plug of the mat into the power outlet. If not, the plug must be plugged in the opposite direction, and then a part of the body must be contacted with the probe terminal to check again, which causes troublesome procedures.

Therefore, the present invention automatically detects the neutral wire, ground or virtual ground regardless of the distribution method or the insertion direction of the power plug, such as a one-wire grounding zone or a neutral grounding zone, when using an electric mat. ) Is to provide automatic shielding device for harmful electromagnetic waves of electric mats.

In order to achieve the above object, a clock signal for supplying a clock signal of AC 60 Hz to a clock terminal of a binary counter, a switch for supplying or blocking the clock signal to a binary counter, and a ring counter according to the input of a clock signal. While the binary counter for outputting the status signal, the display unit for displaying the operation state of the binary counter, and the output of both ends of the binary counter is all 'H', the ground counter is not found, so reset the binary counter. An initializing unit for renewing the ring counter, a driver for amplifying the output signal of the binary counter unit with a signal of a large force, and one of an AC1 power source, an AC2 power source, a ground wire, or a virtual ground depending on the output state of the binary counter unit; It consists of a transition that finds support and connects to the shield.

In addition, when the display unit and the touch unit are connected in series to one end of the shield plate and the shield plate is connected to a hot power source, when the human body having the ground potential contacts the touch unit, the display unit is turned on by the potential difference so that the shield plate is grounded safely. Make it easy to check.

In addition, the shielding plate is automatically grounded without the need for changing the power plug, regardless of other power distribution methods such as a one-wire grounding zone or a neutral grounding zone having a virtual ground.

1 is a circuit block diagram of a harmful electromagnetic wave automatic shielding device of the present invention.

2 is a circuit block diagram of another embodiment of the automatic electromagnetic wave shielding device of the present invention.

Figure 3 is a circuit diagram of one embodiment of the automatic electromagnetic wave shielding device of the present invention.

4 is a time chart of the harmful electromagnetic wave automatic shielding device of the present invention.

5 is a power distribution diagram of various ways applicable to the present invention.

<Explanation of symbols for the main parts of the drawings>

(10)-clock signal section (20)-switch section

(30)-2 binary counter (40) (50)-driver section

(60)-switching unit (70) (110)-indicator

(80)-Initiator (90)-AC1 Power

(100)-AC2 power supply (120)-Touch

(Q1 to Q3)-transistor (R)-resistance

(U1) -binary counter (SB)-shield

(PB)-Push switch (T)-Touch terminal

(PC1) (PC2)-Photocoupler (F)-Fuse

(FR)-Fuseable (C)-Capacitor

(D)-Diode (ZD)-Zener Diode

(NEON)-neon light (NTC)-NCC element

(H)-Electric Plate (PP)-Power Plug

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit block of an embodiment of the present invention, by using a binary counter without looking into a variety of power distribution scheme as shown in Figure 5 AC1 power source or AC2 power source or ground wire or a virtual power source to find one of the shielding plate and It will be connected automatically.

Looking at the circuit block, the clock signal unit 10 for supplying a clock signal of AC 60 kHz to the clock terminal of the binary counter unit 30, and the binary signal unit 30 to supply or block the clock signal The switch unit 20, a binary counter unit 30 for outputting a status signal while ring-counting in response to the input of the clock signal, and a display unit 70 for displaying the operating state of the binary counter unit 30. And an initialization unit 80 which resets the binary counter unit 30 so as to reset the ring counter when the outputs of both ends of the binary counter unit 30 are all 'H'. The driver unit 40 (50) for amplifying the output signal of the binary counter unit 30 to a signal of great power, and the AC1 power source 90 or the AC2 power source (depending on the output state of the binary counter unit 30). 100) or a grounding line or a virtual ground and one of the switching unit 60 for connecting to the shield plate (SB) to find.

The shielding plate SB shields harmful electromagnetic waves emitted while positioned above or below the heat transfer plate H of the electric mat.

2 is a circuit block of another embodiment of the present invention to check whether the shielding plate SB is grounded. The shielding plate is connected to the display unit 110 and the touch unit 120 in series at one end of the shielding plate SB. When (SB) is connected to a hot power source, when the human body having a ground potential contacts the touch unit 120, the display unit 110 is turned on by the potential difference so that the shield plate SB is not grounded. will be.

3 is a detailed circuit diagram of an exemplary embodiment of the present invention, in which a ground line GND, an AC1 power line, and an AC2 power line are respectively connected to a power plug PP having a plurality of terminals, and a temperature setting part is provided in the AC1 power line and the AC2 power line. The temperature control unit and the heat transfer plate H are connected to enable the user to adjust the temperature of the electric mat to a desired temperature, and the shielding plate SB is connected to the ground line GND through a fuse resistor FR.

The heat transfer plate (H) and the shielding plate (SB) is built in the electric mat, the temperature sensor installed on one side of the inside of the mat is connected to the temperature control unit and the heat generating temperature of the electric mat is kept constant at a set temperature, AC2 power line and The fuse F is connected in series between the temperature control part, and the switch SW which serves as temperature setting is connected between the AC1 power supply line and the temperature control part.

In addition, the AC1 and AC2 power terminals use capacitors C2, C7, C8, NTC elements NTC, rectifier diodes D1, D2, and Zener diodes ZD. Operational power is supplied to the harmful electromagnetic wave automatic shielding device of the invention electric mat.

In addition, a current limiting circuit composed of resistors R13 (R14) and capacitor C9 is connected between the AC1 power supply terminal and the light receiving element of the photocoupler PC1, and the AC2 power supply terminal and the light receiving element of the photocoupler PC2 are connected. An operation indicator light D4 having a pull-up resistor R12 connected to the AC1 terminal to which a current limiting circuit consisting of resistors R15 and R16 and a capacitor C6 are connected, and having a power switch SW connected thereto. By connecting to the operating state of the automatic electromagnetic wave shielding device of the present invention is displayed.

The current limiting circuit composed of resistors R13, R14, R15, R16 and capacitors C6, C9 connected to the light receiving element portions of the photocouplers PC1, PC2 includes photocoupler PC1 ( PC2) is composed of symmetrical circuits, and by limiting the current, AC1 power and AC2 power flows when the shield plate SB is electrically connected to the human body due to sweat or moisture (leakage or electric shock). Protect the human body.

In addition, the current limiting circuit prevents a short circuit when the photocoupler PC1 and PC2 are turned on at the same time because AC1 power and AC2 power are respectively applied to the light receiving elements of the photocoupler PC1 and PC2. do.

On the other hand, the current limiting resistor R7 and the push switch PB are connected to the AC2 power terminal and the clock terminal CK of the binary counter (ring counter U1), and the push switch PB is pressed to ON. In this case, a clock signal of 60 Hz is input to the clock terminal CK of the binary counter U1 so as to ring the counter, and the capacitor C1 is connected to the clock terminal CK of the binary counter (ring counter U1). ) And a stabilization circuit composed of a resistor (R6).

The resistor R1 is connected to the reset terminal RES and the output terminal Q6 of the binary counter U1, and a diode (B) between the reset terminal RES and the output terminal Q7 of the binary counter U1. D3) is connected, but the anode of the diode D3 is connected to the output terminal Q7 of the binary counter U1 to form a reset circuit.

In the reset circuit, if the outputs Q6 and Q7 of both ends of the binary counter U1 are all 'H', the ground power source cannot be found. At this time, the binary counter U1 is reset to make a new counter.

A counter display means composed of transistors Q3, resistors R9, R10, R11, capacitors C3, C4, and indicator light D5 is connected to the output terminal Q4 of the binary counter U1. do.

The display means is a capacitor (C4) when the push switch (PB) that the user presses to check whether the shield is turned off (OFF) so that the output of the binary counter (U1) stops in the 'H' or 'L' state Since the indicator D5 turns off when charged, the indicator D5 turns on only during the period in which the capacitor C4 is charged, even when the DC output is input from the transistor Q3, thereby indicating the counter state.

A fuse (FR), a neon lamp (NEON), a current limiting resistor (R8), and a touch electrode (T) are connected in series to the ground terminal (GND) of the power plug (PP). The output terminals of the shielding plate SB and the photocoupler PC1 and PC2 are respectively connected between the neon lamps NEON.

The fuselable resistor (FR) limits the current when the shielding plate (SB) and a hot wire are connected, and a situation in which an electric shock or an electric shock is applied through the shielding plate (SB) or the heating plate (H) and the shielding plate (S) are short-circuited. ), The safety circuit that disconnects the ground wire is fulfilled.

That is, the fuse resistor FR connected to the ground terminal GND of the power plug PP has a shielding plate SB and a heating plate H due to the peeling of the neighboring heat transfer plate H and the insulation breakdown. In the case of a short circuit, there is a risk of fire, short circuit, electric shock, etc. In this case, the fuse resistor FR is melted to protect the circuit of the electric mat and the temperature controller.

Automatic shielding device for harmful electromagnetic waves of the electric mat of the present invention is to find a ground line of the AC1, AC2 power source to ground the shield plate (SB) or to ground with a ground wire or a virtual ground.

For example, when the AC1 power source is grounded, the photocoupler PC1 is turned on, and the shield plate SB is connected to the AC1 power source and grounded.

If the AC2 power is grounded, the photocoupler PC2 is turned on and the shield plate SB is connected to the AC2 power source. Therefore, the shield plate SB becomes a ground potential to block harmful electromagnetic waves. If no ground is found, the virtual ground is found and grounded.

When a 60 kHz clock signal is inputted from the AC power supply to the clock terminal CK of the binary counter (or ring counter U1), a ring counter starts to output to the output terminal of the binary counter U1. The status signal of is output.

Further, even when the shield plate SB is connected to a hot line of the AC power source, the shield plate SB is automatically grounded by the binary counter U1 and the photo coupler PC1 and PC2.

In the present invention, even when the human body is in contact with the touch terminal T in the state that the shield plate SB is grounded, since the potential difference for turning on the neon light NEON does not occur, the neon light NEON is not turned on. .

Table 1 below is an output condition table of the binary counter U1, and FIG. 4 is an output waveform diagram of the binary counter U1.

If the Q6 and Q7 terminal outputs of the binary counter (U1) are in the 'H' state, respectively, as shown in Table 1 below, the binary counter (U1) is not necessary because ground, ground, virtual ground, and neutral lines cannot be found. ) Is initialized.

The reset circuit includes a resistor R1 and a diode D3 connected to the reset terminal RES of the binary counter U1 and the output terminals Q6 and Q7 of the binary counter U1, respectively. When the output terminals Q6 and Q7 of the binary counter U1 are each in the 'H' state, the reset terminal RES of the binary counter U1 is initialized to 'H'.

(Table 1) Output status condition table of binary counter.

Q6 of binary counter (U1) Q7 of binary counter (U2) Other 1 stroke H L Connected to AC2 power (1-wire ground) 2 stroke L H Connected to AC1 power (1-wire ground) 3 stroke L L Connected to AC1, AC2 power (virtual ground) 4 stroke H H Reset the binary counter

On the other hand, since the human body has a potential similar to or equal to the ground potential, which is the surrounding potential, when a hot potential is applied to the shielding plate SB when the human potential is viewed as the ground potential, the human body having the ground potential touches it. When the electrode T is touched, a potential difference is generated at both ends of the neon lamp NEON, and current flows.

Therefore, since the neon light NEON is turned on, it is easy to recognize that hot power is applied to the shield plate SB. In this case, when the push switch PB is pressed, the clock terminal CK of the binary counter U1 is pressed. A counter is started by inputting a clock signal of AC 60 Hz, and a signal of an 'H' or 'L' active state is output to the output terminals Q6 and Q7 of the binary counter U1.

That is, when 'H' is output to the output Q6 of the binary counter U1 and 'L' is output to the output Q7 of the binary counter U1, the transistor Q2 is turned on. Photocoupler PC2 is turned on.

Accordingly, since the AC2 power source is connected to the shield plate SB through the light receiving units of the resistors R16, R15, the capacitor C6, and the photocoupler PC2, the shield plate SB is grounded.

In the state where the shield plate SB is grounded, even when the human body is in contact with the touch terminal T, the potential difference for turning on the neon light does not occur so that the neon light is not turned on. When the push switch PB held down in the state is released (OFF), the supply of the clock signal supplied to the binary counter U1 is cut off and the counter is stopped.

Therefore, since the output state of the binary counter U1 is maintained as it is, the ground of the shielding plate SB is continuously maintained.

In addition, when 'L' is output to the output Q6 of the binary counter U1 and 'H' is output to the output Q7 of the binary counter U1, the transistor Q1 is turned on. Therefore, the photocoupler PC1 is turned on.

Accordingly, since the AC1 power source is connected to the shield plate SB through the light receiving units of the resistors R13, R14, capacitor C9, and photocoupler PC1, the shield plate SB is grounded. When the push switch PB is released (OFF), the clock signal supplied to the binary counter U1 is cut off, the counter is stopped, and the output state of the binary counter U1 is maintained. Grounding is maintained.

In addition, if the ground cannot be found by the AC1 power supply and the AC2 power supply, 'L' is output to the output (Q6) of the binary counter (U1), and 'L' is output to the output (Q7) of the binary counter (U1). In this case, since the two transistors Q1 and Q2 are turned on at the same time, the two photocouplers PC1 and PC2 are also turned on at the same time.

Accordingly, AC1 power is connected to shielding plate SB through resistors R13, R14, capacitor C9, and photocoupler PC1, and AC2 power is resistor R16, R15 and capacitor C6. And the shield plate SB through the light receiving unit of the photocoupler PC2.

At this time, since the shielding plate SB is connected to the intermediate point of the photocoupler PC1 and PC2, the ground potential (virtual ground) of the shielding plate SB is achieved because it is virtually grounded with the same potential. When the push switch PB is released (OFF), the supply of the clock signal supplied to the binary counter U1 is cut off, the counter is stopped, and the output state of the binary counter U1 is maintained. PC2) is continuously turned on, and the ground of the shield plate (SB) is also continuously maintained.

In this case, resistors R13 (R14) and capacitor C9 connected to photocoupler PC1 and resistors R15 (R16) and capacitor C6 connected to another photocoupler PC2 have the same time constant. When AC1 and AC2 power are applied to both ends of the photocoupler PC1 and PC2, the point where the light receiving element of the photocoupler PC1 and PC2 is connected becomes a virtual ground potential of 1/2 potential, The shielded plate SB is virtually grounded to block harmful electromagnetic waves.

Further, the resistors R13, R14, R15, R16 and capacitors C6, C9 connected to the light receiving element portions of the photocouplers PC1, PC2 are centered on the photocouplers PC1, PC2. It configures a symmetric circuit, and by limiting the current, if the shielding board (SB) is electrically connected to the human body due to sweat or moisture (leakage or electric shock), AC1 power and AC2 power are limited, thus protecting the human body. Since the AC1 power and the AC2 power are applied to both ends of the light receiving elements of the photocoupler PC1 and PC2, the short circuit is prevented when the photocoupler PC1 and PC2 are turned on at the same time.

Of course, in the present invention, if there is a separate ground terminal (GND) in addition to the AC1, AC2 power terminal in the power plug (PP), the ground terminal (GND) when there is a ground terminal in the outlet portion to which the power plug (PP) is coupled Grounding of the shield plate (SB) is automatically made through.

In addition, when 'H' is output to the output Q6 of the binary counter U1 and 'H' is output to the output Q7 of the binary counter U1, the ground line, the virtual ground line, the neutral line, etc. Since it is not found, the reset terminal RES of the binary counter U1 is initialized to the 'H' state by the reset circuit composed of the resistor R1 and the diode D3.

In addition, since the transistors Q1 and Q2 and the photocouplers PC1 and PC2 maintain their turn-off states, they do not affect the shield plate SB, and the shield plate SB is grounded. Since it is connected to the terminal GND, the ground state is maintained.

In the present invention, the photocoupler (PC1) (PC2) is to achieve electrical insulation while transmitting a signal, of course, while using the relay (relay), etc. instead of the photocoupler (PC1) (PC2) to achieve electrical insulation. It is desirable to be able to.

In addition, the present invention is a one-wire power ground area or a neutral power ground area, for example, single-phase two-wire wiring area, single-phase three-wire wiring area, three-phase three-wire (Y) wiring area, three-phase three-wire type (△) as shown in FIG. Wiring area, 3-phase 4-wire (Y) wiring area, 3-phase 4-wire (△) wiring area, etc. G) or the virtual ground G is automatically connected with the shield plate SB so that the ground of the shield plate SB is achieved.

In the present invention, the touch terminal T and the push switch PB may be integrally formed. That is, the touch terminal T made of a conductor such as a metal may be used as a push button of the push switch PB, and the touch terminal T may be electrically insulated from the push switch PB.

In the present invention, since a slight current flows through the current limiting resistor R8 and the neon lamp NEON connected to the touch terminal T, the electric shock of the user is prevented.

In the present invention, the grounding construction is fortunately used in the place where the electric mat is used, and when the ground line GND is connected to the earth, the shield plate SB is directly grounded to the earth via the fuseable resistor FR. No switching is necessary and there is no need to replace the power plug (PP) coupled to the power outlet.

In the present invention, some of the indicators preferably use a low power, high brightness light emitting diode (LED).

The present invention as described above has been exemplified as blocking harmful electromagnetic waves by applying to an electric mat, but is not limited to the present embodiment and the accompanying drawings, various substitutions, modifications within the scope not departing from the technical spirit of the present invention And it is possible to change, which will be apparent to those of ordinary skill in the art.

As described above, the present invention has no hassle of switching to the existing slide switch, and it is easy to use because it automatically finds and connects a ground source using a touch and a button.

In addition, it can be used in any power area, and it has an effect of fast response speed, high reliability, and excellent safety.

Claims (6)

A harmful electromagnetic shielding apparatus for an electric mat having a shielding plate, comprising: a clock signal for supplying a clock signal of AC 60 Hz to a clock terminal of a binary counter, and a switch unit for supplying or blocking the clock signal to a binary counter; A binary counter for outputting a status signal while being countered by the input of a clock signal, a display for displaying an operation state of the binary counter, and a binary counter if the outputs of both ends of the binary counter are all 'H' A driver for amplifying the output signal of the binary counter unit, and switching to find and connect at least one ground source of AC1 power source, AC2 power source, ground line, or virtual ground to the shielding plate according to the output state of the binary counter. Automatic shielding device for harmful electromagnetic waves of electric mat consisting of negative parts. The shielding device for harmful electromagnetic waves of an electric mat according to claim 1, wherein a display portion and a touch portion are connected in series to one end of the shielding plate. The binary signal counter terminal according to claim 1 or 2, wherein a means for controlling the input of the clock signal is connected to the clock signal input terminal of the binary counter, and AC1 power and AC2 power are respectively supplied to two outputs of the binary counter. Automatic shielding device for harmful electromagnetic waves of an electric mat, comprising a switching unit which connects a photocoupler to each other and finds at least one ground source among an AC1 power source, an AC2 power source, a ground wire, and a virtual ground and connects the shield plate. In a harmful electromagnetic shielding device of an electric mat having a shielding plate, a capacitor (C2) (C7) (C8), an NTC element (NTC), a rectifier diode (D1) (D2) and a zener diode (AC1, AC2) And a current limiting and bias circuit composed of resistors R13 (R14) and capacitors (C9) between the AC1 power supply terminal and the light receiving element of photocoupler PC1. A current limiting and bias circuit consisting of resistors R15 (R16) and capacitor C6 is connected between the power supply terminal and the light receiving element of photocoupler PC2, and the AC2 power supply terminal and the clock terminal of the binary counter U1 are connected. The current limiting resistor R7 and the push switch PB are connected to CK, the capacitor C1 and the resistor R6 are connected to the clock terminal CK of the binary counter U1, and the binary counter is connected. The resistor R1 is connected to the reset terminal RES of the U1 and the output terminal Q6, and between the reset terminal RES and the output terminal Q7 of the binary counter U1. Connect the anode D3, connect a fuse resistor FR, a neon lamp, a current limiting resistor R8, and a touch electrode T in series with the ground terminal GND, and connect the fuse resistor FR. And the output terminal of the shield plate SB and the photocoupler PC1 (PC2) between the &lt; RTI ID = 0.0 &gt;) &lt; / RTI &gt; and NEON, and the resistors R3 and R5 are connected to the output terminal Q6 of the binary counter U1. A drive composed of transistor Q1 is connected, a light emitting element of photocoupler PC1 is connected to the output of the drive, and resistors R2 and R4 are connected to an output terminal Q7 of binary counter U1. A device for automatically shielding harmful electromagnetic waves of an electric mat, by connecting a drive comprising a transistor (Q2) and connecting a light emitting element of a photocoupler (PC2) to an output of the drive. 5. The resistors R13 and R14 and capacitor C9 connected to the photocoupler PC1 and the resistors R15 and R16 and capacitor C6 connected to the other photocoupler PC2 are respectively. Automatic shielding harmful electromagnetic waves of the electric mat, characterized in that to have the same time constant. 5. The output terminal Q4 of the binary counter U1 is composed of a transistor Q3, resistors R9, R10, R11, capacitors C3, C4, and an indicator light D5. Automatic shielding device for harmful electromagnetic waves of the electric mat by connecting the counter display means.