Sharp R-930AW Absolute Humidity Sensor Circuit, Structure of Absolute Humidity Sensor

Page 27

R-930AK

R-930AW

Pin No.

Signal

I/O

Description

48

P10

OUT

Segment data signal.

 

 

 

Signal similar to P23.

 

 

 

Key strobe signal.

 

 

 

Signal applied to touch-key section. A pulse signal is input to P24-P27 terminal while

 

 

 

one of G-5 line keys on key matrix is touched.

 

 

 

 

49-53

P07-P03

OUT

Segment data signal.

 

 

 

Signal similar to P23.

54-56

P02-P00

OUT

Digit selection signal.

 

 

 

Signal similar to P55.

 

 

 

 

57-59

P37-P35

OUT

Digit selection signal.

 

 

 

Signal similar to P55.

 

 

 

 

60-64

P34-P30

OUT

Used for initial balancing of the bridge circuit (absolute humidity sensor).

 

 

 

 

ABSOLUTE HUMIDITY SENSOR CIRCUIT

(1)Structure of Absolute Humidity Sensor

The absolute humidity sensor includes two thermistors as shown in the illustration. One thermistor is housed in the closed vessel filled with dry air while another in the open vessel. Each sensor is provided with the protective cover made of metal mesh to be protected from the external airflow.

 

 

Sensing part

Sensing part

 

 

(Open vessel)

(Closed vessel)

 

Sensing part

Thermistor

Thermistor

 

(Open vessel)

Ventilation

 

element

element

openings

Sensing part

 

Sensor

 

 

case

 

(Closed vessel)

 

View of sensor case removed

Cross section view

(2)Operational Principle of Absolute Humidity Sensor The figure below shows the basic structure of an absolute humidity sensor. A bridge circuit is formed by two thermistors and two resistors (R1 and R2).

The output of the bridge circuit is to be amplified by the operational amplifier.

Each thermistor is supplied with a current to keep it heated at about 150˚C (302˚F), the resultant heat is dissipated in the air and if the two thermistors are placed in different humidity conditions they show different degrees of heat conductivity leading to a potential difference between them causing an output voltage from the bridge circuit, the intensity of which is increased as the absolute humidity of the air increases. Since the output is very minute, it is amplified by the operational amplifier.

 

 

 

 

Absolute humidity vs,

C

 

Operational

output voltage characterist

R1

amplifier

voltage

 

 

 

Output

 

R2

+

voltage

Output

S

-

S : Thermistor

 

 

 

 

 

 

 

R3

 

 

open vessel

 

 

 

C : Thermistor

 

 

 

 

closed vessel

 

 

 

 

 

Absolute humidity (g/m 2)

(3)Detector Circuit of Absolute Humidity Sensor Circuit This detector circuit is used to detect the output voltage of the absolute humidity circuit to allow the LSI to control sensor cooking of the unit. When the unit is set in the sensor cooking mode, 16 seconds clearing cycle occurs

than the detector circuit starts to function and the LSI observes the initial voltage available at its AN6 terminal. With this voltage given, the switches SW1 to SW5 in the LSI are turned on in such a way as to change the resistance values in parallel with R50-1. Changing the resistance values results in that there is the same potential at both F-3 terminal of the absolute humidity sensor and AN7 terminal of the LSI. The voltage of AN6 terminal will indicate about -2.5V. This initial balancing is set up about 16 seconds after the unit is put in the Sensor Cooking mode. As the sensor cooking proceeds, the food is heated to generate moisture by which the resistance balance of the bridge circuit is deviated to increase the voltage available at AN6 terminal of the LSI. Then the LSI observes that voltage at AN6 terminal and compares it with its initial value, and when the comparison rate reaches the preset value (fixed for each menu to be cooked), the LSI causes the unit to stop sensor cooking; thereafter, the unit goes in the next operation automatically.

When the LSI starts to detect the initial voltage at AN6 terminal 16 seconds after the unit has been put in the Sensor Cooking mode, if it is not possible to balance, of the bridge circuit due to disconnection of the absolute humidity sensor, ERROR will appear on the display and the cooking is stopped.

1) Absolute humidity sensor circuit

 

 

IC2(IZA495DR)

 

 

 

SW1

 

 

 

 

 

 

4

64

 

 

 

 

 

 

P30

 

 

 

 

620k

 

 

 

 

 

 

 

 

5

63

SW2

 

 

 

 

 

 

P31

 

 

 

 

300k

 

 

 

 

 

 

 

 

6

62

SW3

 

 

 

 

 

 

P32

 

 

 

 

150k

 

 

 

 

 

 

 

 

7

61

SW4

 

 

 

 

75k

 

 

 

P33

C. Thermistor in

 

 

 

8

60

SW5

 

 

37.4k

 

 

 

P34

closed vesssl

 

 

 

 

 

 

S. Thermistor in

 

 

 

 

 

 

 

open vessel

 

 

 

 

3

5

AN7

 

 

 

47k

F

F

 

 

 

 

 

F

 

 

 

 

 

 

 

 

 

 

 

0.01

0.015

 

LSI

F-1

11

 

 

0.01

 

C

 

 

 

 

 

 

 

(IC1)

 

 

 

 

 

 

 

 

F-3

3.57k

 

+

 

10k

 

 

 

 

 

 

2

6

 

 

 

 

 

 

S

 

 

0.1 F

 

 

47k

 

AN6

3.32k

-

 

 

 

 

F-2

1.8k

 

 

 

 

 

10

 

 

360k

 

 

 

 

 

 

 

 

 

 

R51

9

 

 

 

 

 

 

 

 

12

 

1

 

 

 

 

 

 

 

 

 

VA : -15V

 

VA : -15V

VC : -5V

 

 

25

Image 27
Contents Convection Microwave Oven Table of Contents930AK 930AW Before Servicing Microwave Measurement Procedure RequirementsLeakage test Foreword Sharp PLAZA, MahwahConvection Microwave Oven 930AK / R-930AWGrounding Instructions SpecificationGeneral Information DescriptionTouch Control Panel Oven DiagramOFF Condition Power Level P-0 to P-90 CookingOperation Description of Operating SequencePreheating Condition Convection Cooking ConditionAutomatic MIX Cooking Condition Sensor Cooking ConditionCooking Sequence Fire Sensing Feature Microwave ModeCompu BROIL/ Compu ROAST/ Compu Bake Compu Defrost CookingFigure O-1. Oven Schematic-OFF Condition Schematic DiagramFigure O-4. Oven Schematic-Convection Cooking Condition Description and Function of Components Damper OPEN-CLOSE Mechanism Troubleshooting GuideHeating Element Convection Cooking SystemPossible Cause Defective Parts Test Procedure ProblemHigh Voltage Rectifier Test Test ProceduresProcedure Component Test Letter Magnetron Assembly Test Power Transformer TestTemperature Fuse Test Procedure Component Test LetterSecondary Interlock Switch Test Monitor SwitchThermal CUT-OUT Test Test Procedures Component Test LetterDamper Switch Test Checking Temperature in the Convection ModeOuter Case Switch Test Touch Control Panel Assembly TestKEY Unit Test Weight 1ST Stage 2ND Stage 3RD Stage 4TH Stage Level Time Relay TestCompu Defrost Test Water load cooking test Occurrence Cause or CorrectionAH Sensor Test Checking the initial sensor cooking conditionR1,R2 22Ω ± R3 4.3kΩ ± 5% 1/4W Test Procedures Letter Component TestTesting Method for AH Sensor AND/OR Control Unit Checking Control UnitThermistor Touch Control Panel AssemblyLSIIZA797DR Description of LSITOR Key strobe signal Signal similar to P27Segment data signals Segment data signalStructure of Absolute Humidity Sensor Absolute Humidity Sensor CircuitServicing Outer Case Removal Component Replacement and Adjustment ProcedureOuter Case Switches Replacement Power Transformer RemovalHigh Voltage Capacitor Removal High Voltage Rectifier Assembly RemovalPositive Lock Connector NO-CASE Type Removal Magnetron RemovalFAN Motor Removal Damper Assembly RemovalTurntable Motor Removal Oven Lamp and Lamp Socket RemovalControl Unit and KEY Unit Control Panel Assembly and Control Unit RemovalAfter adjustment, make sure of the following Door Replacement and AdjustmentAfter adjustment, check the following Door AdjustmentFigure C-5. Door Replacement and adjustment Door DisassemblyFigure S-1. Pictorial Diagram Control Panel CircuitDIP Electrical Parts Cabinet PartsControl Panel Parts VSDTA123ES/-3 Oven PartsDoor Parts MiscellaneousScrews Nuts and Washers Description HOW to Order Replacement PartsPacking and Accessories Model NumberOven Control Panel Parts Door Parts Miscellaneous 930AK 930AW
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R-930AW specifications

The Sharp R-930 series of microwave ovens, including the R-930AK, R-930AW, and R-930CS models, represent a blend of advanced technology and user-centric design. These units are well-suited for modern kitchens, offering convenience, versatility, and efficiency that meet the needs of busy households.

One of the standout features of the R-930 series is the powerful Inverter Technology. Unlike traditional microwaves that rely on pulsing power to cook food at lower settings, Inverter Technology delivers a steady stream of cooking power. This results in more even heating, improved texture, and better overall cooking results for delicate dishes like custards and sauces.

The spacious interior of these models provides ample room for cooking a variety of dishes simultaneously. The R-930 series is designed with a turntable that ensures uniform cooking by rotating food as it heats. Additionally, these microwaves often come with a variety of pre-programmed settings for popular dishes, making it easier for users to prepare meals with minimal effort. These presets take the guesswork out of cooking and help ensure consistent results every time.

The R-930AK and R-930AW models are particularly noted for their sleek and modern aesthetic, available in stylish black and white exteriors, respectively. Both models also feature user-friendly controls, which include a digital display and intuitive buttons, ensuring that even those new to microwave cooking can navigate settings with ease.

Another characteristic that distinguishes the R-930CS is its advanced sensor cooking technology. This feature monitors the cooking process and automatically adjusts power levels and cooking times to achieve optimal results. This takes the hassle out of determining how long to cook various foods, especially those that require specific attention to avoid overcooking or undercooking.

The Sharp R-930 series also emphasizes safety and convenience. Child safety locks are integrated into the design to prevent unauthorized use, making it a practical choice for families with young children. Moreover, the easy-clean interior ensures that spills and splatters can be quickly wiped away, maintaining hygiene and preserving the appliance's appearance.

In summary, the Sharp R-930AK, R-930AW, and R-930CS models are proficient microwave ovens equipped with innovative technologies and thoughtful features that cater to a variety of cooking needs. With their combination of inverter cooking technology, spacious interiors, sleek designs, and user-friendly controls, these models are ideal choices for anyone looking to enhance their culinary capabilities in a fast-paced world.