KR20020034582A - Key device for microwave oven using change of capacitance thereof - Google Patents

Abstract

PURPOSE: A key system for a microwave oven using the variation of capacitance is provided to improve the convenience of a user by being capable of operating the key system by light contact. CONSTITUTION: A key(18) is protruded into the outside of a microwave oven, and is made of a metal forming an inductive electrode to contact a human body. An oscillator(30) varies an oscillation frequency by coupling inductive capacitance induced from the key with internal capacitance. A controller(40) determines whether the key is input by comparing a count value of the oscillation frequency in non-contact with a count value of the frequency output from the oscillator(30).

Description

Key device for microwave oven using change of capacitance

The present invention relates to a key device of a microwave oven using a change in capacitance.

In the prior art with respect to the switch, tex switches and membrane switches are representative. However, in the case of the tec switch, when used for a long time, wear phenomenon may occur due to mechanical friction, corrosion due to external moisture, and inconvenience in cleaning.

Membrane switches are sensitive to heat, require constant pressure on keystrokes, and can be damaged by sharp objects. In addition, the manufacturing is complicated and difficult disadvantages.

The prior art for switches using capacitives is disclosed in publication 10-1999-0059958. The switch is a switch intended to be used in the elevator as the invention to detect the change in the distance caused by the pressure change of the capacitance of the condenser to operate the switch is simple and the switch is pressed even in the instantaneous or continuous pressure on the piezoelectric element As it can be recognized that the result of the operation, the life and reliability of the switch are improved. However, the switch does not move out of the frame of the push switch because the switch operates only when the distance is changed.

An object of the present invention is to improve the disadvantages of the existing mechanical switch to enhance the image of the product in the key of the microwave oven and to facilitate the user's convenience.

The present invention provides a switch that overcomes such mechanical operation and operates by simply touching it with a permittivity of the human body without using pressure.

According to the present invention, a key made of a metal plate to form an induction electrode portion protruding out of the microwave oven to contact the human body to detect the capacitance by using the dielectric constant of the human body; An oscillator in which an induced capacitance input from the key is combined with an internal capacitance of an oscillator to vary an oscillation frequency; And a controller for counting an output frequency of the oscillator based on a clock frequency and comparing the oscillation frequency stored in a memory with a counted value of an oscillation frequency in a non-contact manner to determine whether a current microwave oven is pressed. A key device for a microwave oven is provided.

In addition, in a microwave oven having a plurality of function keys and a microcomputer for performing a function corresponding to each key, a method of performing a control algorithm for determining whether a key is input by an output frequency generated by a capacitance induced in a key Measuring the output frequency from the key after power up; Storing the output frequency as an initial frequency; Re-measuring the output frequency to determine if the current key has been touched; Determining whether a current frequency is equal to the initial frequency; If the current frequency and the initial frequency is determined to be different from the control unit of the microwave oven comprising the step of performing a key value designation subroutine includes a key device operation method.

The key device using the change of capacitance according to the present invention is a 100% electronic key device, there is no mechanical wear phenomenon, and because the non-dielectric materials such as glass or acrylic can be added to the front of the key, it is possible to have a colorful appearance design and easy cleaning. There is this. In addition, since the operation can be performed only by light contact, user convenience is improved.

1 is a schematic perspective view of a conventional microwave oven.

2 is a block diagram illustrating the concept of the present invention.

FIG. 3 is a configuration diagram showing FIG. 2 in more detail.

4 is a timing diagram showing a change in oscillation frequency in an oscillator.

5 is a flowchart illustrating a control algorithm of the controller in the key device of the present invention.

6 is a flowchart illustrating an algorithm for counting frequencies.

* Explanation of symbols on main parts of the drawings

14: Display 16: Keypad

18: key 30: oscillator

31: oscillator internal capacitance 32: oscillator internal resistance

40: control unit (microcom) 41: memory

42: clock generator

Referring to Figure 1, a schematic perspective view of a conventional microwave oven is shown. The microwave oven 10 includes a door 12, a display unit 14, and a keypad 16. The keypad 16 is provided with a plurality of operable keys 18. The present invention relates to a key device of a microwave oven.

The key device of the microwave oven according to the present invention, as shown in Fig. 2, is composed of a key 18, an oscillator 30, and a control unit 40, the key 18 is made of a metal plate and the user's finger and Made to be in contact Each key 18 is provided with a corresponding oscillator, respectively. The metal plate of the key 18 is connected to the input terminal of the oscillator 30 by a conducting wire, and the oscillation frequency output terminal of the oscillator 30 is connected to the input terminal of the controller (microcomputer) 40. The oscillator 30 and the control unit 40 receive power from the power supply unit 20.

Referring to the detailed circuit of FIG. 3, when power is applied from the power supply unit 20 to the oscillator 30, an intrinsic oscillation frequency as shown in FIG. 4B is output by the internal capacitance 31. The output oscillation frequency is input to the controller 40 and the oscillation frequency count value is stored in the memory 41. At this time, when the finger of the human body contacts the key 18, the output frequency of the oscillator is changed as shown in FIG.

The calculation of the output frequency is calculated as a combination of the internal capacitance of the oscillator and the capacitance induced in the key 18.

Oscillation frequency at non-contact (f) ≒ 1.44 / (Rx / Cx)

Oscillation frequency at contact (f) ≒ 1.44 / (Rx ・ (Cx + Ca))

Where Cx is the oscillator internal capacitance 31 and Ca is the capacitance derived from the key 18. Rx is the oscillator internal resistance.

The changed output frequency is input to the input port of the controller 40, and in the controller MICOM, the clock frequency as shown in FIG. 4A is generated by the clock generator 42 provided therein and counted by the clock frequency. Therefore, it is determined whether a key is pressed by comparing with the oscillation frequency (b) of the non-contacting oscillator which is already stored.

The waveform diagram of FIG. 4 shows that the pulse width of the oscillation frequency (C) during human contact changes more significantly with respect to the oscillation frequency (B) when not in contact.

Referring to the flowchart of FIG. 5, an algorithm for controlling a key device operation by a controller of a microwave oven is illustrated. In step S1, the controller 40 measures the output frequency from the key after power is applied. The process of measuring the output frequency is shown in FIG. 6 and refers to the description of FIG. 6. In step S2, the output frequency is stored as an initial frequency. Then in step 3 the output frequency is remeasured to determine if the current key has been touched. In step 4, it is determined whether the current frequency and the initial frequency are the same. If it is determined in step 5 that the current frequency and the initial frequency are different, a key value designation subroutine is performed. The pulse width of the oscillation frequency is wider at the time of contact than at the non-contact.

Key counter value on contact> Key counter value on non-contact

Becomes In step 5, the keystroke flag is set and the current key counter value is zeroed before the key value assignment subroutine is executed. In order for the key value designating subroutine to perform an operation corresponding to each key, a corresponding operation of each key is programmed in the control unit. In other words, when the key input is confirmed, the program corresponding to the key is executed.

Referring to FIG. 6, a method of measuring the output frequency is illustrated. The controller processes the frequency value as a counter value by the system clock. In step 10, the key scan interrupt is determined by the microcomputer's system clock (Fig. 4A). The key scan interrupter is applied and it is determined whether the input port is high in step 20. If the pulse applied to the input port goes from low to high, the key counter is increased by one in step S30 and the key counter is terminated when it falls from high to low.

The present invention overcomes the disadvantage of operating a constant pressure, which is a disadvantage of the mechanical switch because it uses a key device using a capacitance in the microwave as described above, the non-electric material to the metal plate key By gluing, the exterior decoration can be advanced and the risk of key wear and corrosion can be significantly reduced. In addition, the user's convenience is increased because a part of the human body is able to input a key even if only a slight contact with the induction electrode.

Claims (2)

A key made of a metal plate protruding out of the microwave oven to form an induction electrode part for contacting the human body; An oscillator in which an induced capacitance input from the key is combined with an internal capacitance of an oscillator to vary an oscillation frequency; And A control unit for determining whether a key is input to a current microwave oven by counting an output frequency of the oscillator based on a clock frequency and comparing the counted value of an oscillation frequency at the time of non-contact stored in a memory. Key device. In a microwave oven having a plurality of function keys and a microcomputer for performing a function corresponding to each key, a method of performing a control algorithm for determining whether a key is pressed or not based on an output frequency generated by a capacitance induced in a key includes: Measuring an output frequency from the key after applying power; Storing the output frequency as an initial frequency; Re-measuring the output frequency to determine if the current key has been touched; Determining whether the current frequency is equal to the initial frequency; And performing a key value designation subroutine if it is determined that the current frequency is different from the initial frequency.