Sharp Carousel R-380E, Руководство по обслуживанию

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R-380E
19
(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.
(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, 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.
(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
ABSOLUTE HUMIDITY SENSOR CIRCUIT
than the detector circuit starts to function and the LSI
observes the initial voltage available at its AIN5 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 R98 ~ R102. Changing
the resistance values results in that there is the same
potential at both F-3 terminal of the absolute humidity
sensor and AIN4 terminal of the LSI. The voltage of AIN5
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 AIN5 terminal of the LSI.
Then the LSI observes that voltage at AIN5 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 AIN5
terminal 16 seconds after the unit has been put in the
Sensor Cooking mode, if it is not possible to balance 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
ventilation opening for sensing
Sensing part
(Open vessel) Sensing part
(Closed vessel)
Thermistors
SW1
SW2
SW3
SW4
SW5
P20
P21
P22
P23
P24
LSI
(IC1)
AIN4
AIN5
620k
300k
150k
75k
37.4k
26
23
22
50
49
24
25
15k
15k
4.7k 1 2 3 4
8 7 6 5
0.01uF
0.1uF 0.01uF
VA : -15V VA : -15V
R90 330
C
90
C
91
C
93
C92
S
F-2
1.8k
IC2
F-1
F-3
C
3.57k
3.32k
VC : -5V
0.1 uF
C. Thermistor in
closed vessel
S. Thermistor in
open vessel
R98
R99
R96
R91
360k
R93
R92
R94 R95
D90
R100
R101
R102
R97
C
S
R3
R1
R2
+
Operational
amplifier
Output
voltage
S : Thermistor
open vessel
C : Thermistor
closed vessel
2 Absolute humidity (g/m )
O
utput voltage
Absolute humidity vs,
output voltage characteristic
The relation between signals and LCD are as follows:
LSI signal LCD LSI signal LCD LSI signal LCD
(Pin No.) segment (Pin No.) segment (Pin No.) segment
SEG 39 (103) .......... SEG 1 SEG 25 (117) .......... SEG 15 SEG 12 (130) ........ SEG 28
SEG 38 (104) .......... SEG 2 SEG 24 (118) .......... SEG 16 SEG 11 (131) ........ SEG 29
SEG 37 (105) .......... SEG 3 SEG 23 (119) .......... SEG 17 SEG 10 (132) ........ SEG 30
SEG 36 (106) .......... SEG 4 SEG 22 (120) .......... SEG 18 SEG 9 (133) ........ SEG 31
SEG 35 (107) .......... SEG 5 SEG 21 (121) .......... SEG 19 SEG 8 (134) ........ SEG 32
SEG 34 (108) .......... SEG 6 SEG 20 (122) .......... SEG 20 SEG 7 (135) ........ SEG 33
SEG 33 (109) .......... SEG 7 SEG 19 (123) .......... SEG 21 SEG 6 (136) ........ SEG 34
SEG 32 (110) .......... SEG 8 SEG 18 (124) .......... SEG 22 SEG 5 (137) ........ SEG 35
SEG 31 (111) .......... SEG 9 SEG 17 (125) .......... SEG 23 SEG 4 (138) ........ SEG 36
SEG 30 (112) .......... SEG 10 SEG 16 (126) .......... SEG 24 SEG 3 (139) ........ SEG 37
SEG 29 (113) .......... SEG 11 SEG 15 (127) .......... SEG 25 SEG 2 (140) ........ SEG 38
SEG 28 (114) .......... SEG 12 SEG 14 (128) .......... SEG 26 SEG 1 (141) ........ SEG 39
SEG 27 (115) .......... SEG 13 SEG 13 (129) .......... SEG 27 SEG 0 (142) ........ SEG 40
SEG 26 (116) .......... SEG 14
143 COM7 OUT Common data signal : COM9. Connected to LCD signal COM9.
144 COM6 OUT Common data signal : COM10. Connected to LCD signal COM10.
Pin No. Signal I/O Description