KR870003977Y1 - Control circuit of an electronic range - Google Patents

Abstract

No content.

Description

Microwave Control Circuit

1 is a specific circuit of the microwave control circuit according to the present invention.

2 is a schematic cross-sectional view of a microwave oven in which an absolute humidity sensor is attached to the exhaust port.

3 is a graph showing a relationship between a cooking time during sensor cooking and an output voltage of an operational amplifier.

4A is a relation diagram illustrating a voltage range per unit bit according to a reference voltage.

4b is a voltage response on a unit bit programmed in a microcomputer.

5 is a flowchart of a corresponding time program in time cooking.

6 is an exemplary diagram for explaining a time or temperature setting of a type B variable resistor.

* Explanation of symbols for main parts of the drawings

1 sensor unit 2 reference voltage control unit

3: microcomputer 8: absolute humidity sensor

The present invention relates to a cooking control circuit in a microwave oven, and more particularly, to a circuit that can control cooking according to time or temperature while automatically controlling cooking using absolute humidity.

In a conventional microwave oven, a method of setting a time or temperature by a user and ending cooking when the set time or temperature is reached has been used.

In this time or temperature cooking, for example, if the user wants to heat food for 10 minutes, the number key attached to the operation panel had to be pressed in the order of “1”, “0”, “0”, “0” and temperature. Similarly, in setting, there was an inconvenience in the operation of pressing the numeric keys, and in addition, there was a defect in which the user had no choice other than setting the time or temperature in order to prepare for the purpose.

Accordingly, an object of the present invention is to provide a microwave control circuit capable of both automatic cooking using a sensor and time cooking and temperature cooking.

Still another object of the present invention is to provide a microwave control circuit which can set the time cooking and the temperature cooking of a microwave oven using a variable resistor without using a separate numeric key.

Another object of the present invention is to change the degree of cooking according to the purpose by differently setting the reference voltage of the analog-to-digital (A / D) converter for automatic cooking using a sensor and for cooking time or temperature. The present invention provides a microwave control circuit.

Another object of the present invention to provide a microwave control circuit that can easily detect the failure of the sensor.

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

1 is a specific control circuit diagram of the microwave oven according to the present invention.

In the drawing, the sensor unit 1 is connected to the sensor unit power supply V _BT and the current limiting resistor Rs, and is connected to the exposure type dummyster TH ₁ and the sealed type duster TH ₂ sealed with dry air. ) Is connected to point C in parallel with series resistors R ₁ and R ₂ to ground D point, A point is non-inverting terminal of op amp IC ₁ , B point is inverting op amp IC ₁ through resistor R ₃ It is connected to the terminal and its output terminal is inverted feedback through the resistor R ₄ , and the output voltage Vo ₁ of the discrete op amp IC ₁ is input to the analog input terminal AN ₁ of the microcomputer 3.

The diodes D _l and D ₂ are used to prevent the voltage levels at points B and A from being higher than the voltage Vcc + 0.6 volts. The resistors R ₃ and R ₄ are the amplification resistors of the operational amplifier IC1.

The reference voltage controller _{2 has} a non-inverting terminal (+) of comparator IC ₂ connected to the point A of the sensor unit, an inverting terminal (-) connected to an emitter of transistor Q ₁ , and a resistor R _{5 at} the output terminal of comparator IC ₂ . connected to the power supply Vcc and also connected via the base of transistor Q ₁ via the resistor R _6.

The base of transistor Q ₁ is connected to a Zener diode D ₂ is grounded through a resistance sensor supply unit through the power source V R _{7 BT} and is connected to the collector of transistor Q ₂ through the resistor B _8.

In addition, the emitter of transistor Q ₁ is connected to the high reference voltage input terminal RH of the microcomputer 3 and grounded through the anti-ripple capacitor C ₁ and grounded through the B type variable resistor Rv, and the middle tap of the B type variable resistor. It is connected to the analog input terminal of the AN ₂ Computer 3 to the dyke.

On the other hand, the emitter of the transistor Q ₂ is connected to the power supply Vcc and the base is connected to the output terminal OUT ₁ of the microcomputer 3 through the resistor R ₉ , and this output terminal is connected to the power supply Vcc through the resistor R ₁₀ to the microcomputer 3. Pull up the output from.

On the other hand, the microcomputer low reference voltage input terminal RL is grounded to zero. Here, the high and low reference voltage input terminals RH and RL are reference voltage input terminals of the A / D converter built in the microcomputer 3. The interface unit 4 receives a signal output from the microcomputer 3 to turn on and off the magnetron 6 that generates microwaves, and outputs a number to the display device unit 5 that indicates cooking time or cooking temperature. It also serves to transmit a command to the microcomputer 3 by inputting an operation signal of the key input unit 7.

On the other hand, the absolute humidity sensor 8 of the sensor unit 1 is attached to the exhaust port 10 as shown in the front sectional view of the microwave oven of FIG.

In addition, the B type variable resistor Rv is attached to the operation panel of the key input unit 7 so that the user can adjust the rotation.

Suppose that the user of the microwave oven now places the cooking food 11 on the countertop 12 as shown in FIG. 2, selects the automatic cooking key of the key input unit 7, and presses the start key to perform automatic cooking. .

The absolute humidity sensor (8), consisting of an exposed dummy dust TH ₁ through which external air can freely enter the power supply and a sealed dummy dust TH ₂ sealed in dry air with an absolute humidity of 0, provides a current limit from the sensor power supply V _BT . The current flows through the melt resistance Rs, and the dummy dusts TH ₁ and TH ₂ constituting the absolute performance sensor 8 become self-heating and are heated to about 200 ° C to 300 ° C.

At this time, the B point of the absolute humidity sensor and the A point between the resistors R _l and R ₂ are to be in equilibrium.

In other words, at the initial stage of sensor cooking, the voltage V _BD between the B and D points and the voltage V _AD between the A and D points are adjusted equally.

As shown in FIG. 2, when the magnetron 6 oscillates and releases microwaves into the cooked food, water vapor is generated in the food 11 after a predetermined time, and the water vapor is discharged to the outside through the exhaust port. Is absorbed by the absolute humidity sensor (8). At this time, moisture is adsorbed to the exposed dummy duster TH ₁ constituting the absolute humidity sensor 8, and the adsorbed moisture vaporizes by heating of the exposed dummy dust TH ₁ , and its temperature decreases. TH ₂ is completely airtight with dry air, so its temperature does not change.

Therefore, the resistance of the surface-type more Mr TH ₁ having characteristics that the temperature and resistance inversely proportional are increases voltage V _AD between point B and point D, the voltage V _BD, and a point A and a point D between is causing the potential difference between the voltage V _BD and V _AD are respectively input and amplified to the inverting terminal (-) and the non-inverting terminal (+) of the operational amplifier IC ₁ , and the output voltage Vo ₁ is expressed by the following equation.

In the initial cooking As can be seen this expression chulryeon voltage Vo of ₁ V _AD = V op amp IC _{1 BD} so it can be seen that the V _AD. In the food 11 and will continue to give off water vapor The water vapor resistance of the surface-type more Mr TH ₁ is vaporized adsorbed on the exposed further Mr TH ₁ on the countertop 12, the cooking time more flows are fades As a result, the potential difference V _AD -V _BD between the points A and B also becomes larger.

Therefore, the output voltage Vo _l of the operational amplifier IC ₁ increases.

However, when it comes to jongrojeom of cooking becomes the amount of water vapor discharged from the predetermined food (11) so to transfer constant of water vapor that is vaporized in the adsorption Exposed more misses TH -V ₁ site V _{AD BD} are staying in a certain point the operational amplifier IC there is the output voltage Vo reaches the _first predetermined value, also in this case ₁ is the end point of cooking.

Therefore, if the type of food is the same, the output level is constant regardless of the size or quantity of the food, large or small, or large or small.

Law of Energy Ball = Magnetron Output Energy = Energy Emitted by Water Vapor

This is because it detects and amplifies the absolute humidity emitted from food.

Such a characteristic is shown in FIG. Curve (a) in the figure is a large amount of cooked food and the curve (b) is a relationship curve of the output voltage Vo _l of the operational amplifier according to the cooking time when the amount of cooked food is small. Where V _RH and V _RL are the high and low reference voltages of the microcomputer 3, and the terminal voltages of the terminal RH of the microcomputer 3 of FIG. 1 are input to the RL.

Therefore, the reference voltage range of the A / D converter built in the microcomputer 3 is at the minimum point V _RL = 0 and the maximum point V _RH , and this reference voltage V _RH must be A when automatic cooking using absolute humidity sensor. It must be larger than the output voltage of the operational amplifier IC ₁ at the end of cooking because it is larger than the voltage V _AD at the point.

Therefore, an inverting terminal of the comparator IC ₂ (-) voltage inputted to the V _RH is due to greater than the voltage V _AD, which input to the non-inverting input terminal the comparator IC ₂ outputs are to be in the low state and the output terminal OUT ₁ of the Micro Computer (3) Turn transistor Q ₂ off by setting the output of the signal to high.

In this state, the reference voltage V _RH is determined by the values of the resistors R ₅ , R ₆ , and R ₇ , and does not depend on the breakdown voltage of the zener diode DZ, that is, V _DZ divided by the resistors R ₆ , R ₇ here as Zener diode (DZ) the breakdown voltage less than a set at a constant value of V _RH by controlling the transistor (Q ₁₎ in a conductive state, in the Zener diode state ignore the fine current flowing to the (DZ) the transistor (Q ₁₎ This results in the current flowing through the resistor (R ₇ ) minus the current flowing through the resistor (R ₇ ) from the current flowing through the resistor (R ₆ ) .This base current is multiplied by the amplification degree (hfe) of the transistor (Q ₁ ) to determine the emitter current. _{Allow the} V _RH value to be set.

This is the reference voltage of the A / D converter of the microcomputer 3 during the automatic cooking. When V _RH is reduced as shown in Fig. 4a, the degree of cooking is improved, but this reference voltage V _RH is Similarly, in automatic use of the sensor, the potential of the point A must be higher than that of V _AD , and smaller than when the absolute humidity sensor 8 is disconnected.

That is, the values of the resistors R ₁ and R ₂ are set to satisfy the following equation.

Where (R ₁ + R ₂ ) // (R _TH1 + R _TH2 ) is the parallel synthesis resistance of the resistance values (R ₁ + R ₂ ) and (R _TH1 + R _TH2 ), and R _TH1 and R _TH2 are _{dummy spurs} TH Resistance values of ₁ and TH ₂ . Therefore, FIG. 4A illustrates that the degree of cooking is improved when the reference voltage V _RH is reduced. 4A shows the relationship between the reference voltage of the A / D converter of the microcomputer 3 and one bit per hexadecimal display. It can be seen that the voltage range per bit decreases as the reference voltage V _RH decreases.

I.e., in a reference voltage V to 5 volts, and, _RH2 if the reference voltage V _RH1 to 3 volts hexadecimal 38 and a small reference voltage V _RH1 than 39 the reference voltage V _RH2 in one bit as shown in claim 4a Fig. It can be seen that the incremented voltage range is smaller (ΔV ₁ <ΔV ₇ ). For example, if the counter of the A / D converter of the microcomputer 3 is composed of 8 bits, it can be represented as ² hexadecimal bits (16 ² = 256) with 256 memory in decimal number, and from 0 to 255 in decimal address. I can remember it.

Therefore, the standard full range V _RH -V _RL is The 8-bit binary display and the 2-bit hexadecimal display corresponding to the addresses 0 to 255 in the present invention are divided into = × (V _RL = 0 in the present invention) and the corresponding analog voltages are shown in FIG. 4B.

Therefore, each incremented voltage range ΔV ₁ is about 11mV and ΔV ₂ is about 19mV.

On the other hand, since the reference voltage V _RH is set to be smaller than the value of V _AD when the absolute humidity sensor 8 is disconnected as described above, when the absolute humidity sensor 8 starts the microwave when disconnected, A / D conversion is performed before cooking starts. Results in a maximum of FF so that the microcomputer 3 can easily detect a sensor failure. That is, V _RH becomes (V _DE -on) V as the output Vo ₂ of IC ₂ goes high, but is smaller than V _AD .

On the other hand, when the user wants to cook time or temperature, press the start key of the key control unit 7 and press the key of time or temperature so that the output of the output terminal OUT ₁ of the microcomputer 3 goes low and the transistor Q ₂ Is turned on and the power supply voltage Vcc is energized regardless of the high or low state of the output voltage Vo ₂ of the comparator IC ₂ through the resistor R ₈ so that the zener voltage V _DZ and the transistor (Q1) of the zener diode are turned on. V _RH is always V _D2 -0.7 = V _RH2 due to meter-to-meter voltage of 0.7 volts at the base of

Therefore, this value can be selected to a value different from the above-mentioned reference voltage V _RH using the sensor, and thus cooking can be made according to the user's desired use by varying the cooking degree according to the cooking purpose.

When the user sets the cooking time or the cooking temperature, the cooking time or the cooking temperature can be set by rotating the B-type variable resistor Rv of the key control unit 7. Such a time setting or the temperature setting is performed by the microcomputer 3. You can cook in the program.

5 is a flowchart of a cooking example that is programmed by performing the case of time. When the internal counter of the A / D converter of the microcomputer 3 is composed of 8 bits, it corresponds to 2 ⁸ = 256 in decimal and 2 bits (16 ² = 256) in hexadecimal.

Therefore, the time response corresponding to the decimal digit index can be stored in the memory RAM, and the voltage V _RL distributed from the B type variable resistor to the intermediate tap can be spread to the decimal address as shown in FIG. 4 (b). When the time conversion ratio corresponding to the number is output to the display device, the time can be set by rotating with a B type variable resistor. Decimal index and hexadecimal display and time conversion table according to the example is as follows.

The order of the fifth-degree time conversion program when "the voltage value that is the mode of the cooking time by rotating a B-type variable resistor input to the analog input terminal AN ₂ of Micro Computer (3) V _RV referred to as follows:

The reference voltage range V _RH -V _RL of the microcomputer 3 is divided into 256 intervals of 255 intervals, one of which is set to X, and the voltage value of V _RV is divided by the division value of X to A.

Output the decimal address corresponding to A to the display device ”.

Therefore, when the time is output to the display device and the user presses the ignition key, the time indicated on the display device is reduced by one second while the microcomputer 3 oscillates the magnetron 6 through the interface unit 4. When it reaches zero, time cooking ends.

In the case of temperature cooking, as described above, the temperature to be cooked can be set, and in order to actually cook, a temperature sensing element and an associated circuit are required. Only setting method is illustrated.

On the other hand, even when there is a difference in the reference voltage V _RH in the control circuit of FIG. 1 during the time or temperature cooking, there is no time or temperature setting error.

FIG. 6 shows the type B variable resistor RV, where A is the grounded point, B is the point connected to the reference voltage input terminal RH of the microcomputer 3, and the scale indicates point C. The length between A and C If the length between a, c and B is b, the division X in FIG. And the voltage V _RV inputted to the analog input terminal AN ₂ of the microcomputer 3 is Becomes

The decimal number A is It can be seen that it is independent of the reference voltage V _RH .

As described above, the present invention can adjust the reference voltage input to the A / D converter at the time of cooking the sensor and at the time of cooking or temperature cooking, thereby not only changing the cooking degree according to the purpose but also determining whether the sensor is abnormal. In addition, the time and temperature setting is not performed by the numeric keys, but the simple operation of the variable resistor has the advantage of easy operation.

Claims (1)

In the control device of a microwave oven using a microcomputer, the absolute humidity sensor (8) and the resistance (R _l ), (R ₂ ) is composed of a bridge, the midpoint and resistance (R ₁ ) of the absolute humidity sensor (8). , The sensor unit 1 and the resistors R ₁ and (R ₂ ) connected to the operational amplifier IC _{1 with} the midpoint of (R ₂ ) connected to an analog input terminal AN ₁ of the microcomputer. ₂₎ of the middle point and the input of the transistor (Q ₁₎ emitter a comparator (IC ₂₎ of the terminal and connected to the transistor output terminal of the comparator _{(IC 2) (Q 1)} , (Q 2) and a Zener diode (DZ) And a reference voltage generating circuit composed of resistors (R ₅ ) and (R ₁₀ ), and inputting the reference voltage to the reference voltage terminal (RH) of the microcomputer (3) for time cooking or temperature cooking and cooking using the sensor. Connect the reference voltage control unit 2 and the variable resistor VR configured to set the reference voltage differently from the reference voltage terminal RH. The middle tap is connected to the analog input terminal (AN ₂ ) of the microcomputer 3 to set the cooking time or cooking temperature to the variable resistor RV, and the reference voltage V _RH can be changed according to the cooking mode. Microwave oven control circuit characterized by the configuration which makes it possible to change the resolution degree.