Sharp Carousel R-380L Servis Kılavuzu - Sayfa 18

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Sharp Carousel R-380L Servis Kılavuzu
R380L(W)
CHAPTER 9.
R380L(W)
TOUCH CONTROL PANEL ASSEMBLY

[1] OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following units.
(1) Key Unit
(2) Control Unit (The Control Unit consists of Power Unit and LSI Unit).
The principal functions of these units and the signals communicated among them are explained below.
1. Key Unit
The key unit is composed of a matrix, signals generated in the LSI are sent to the key unit through P00-P07.When a key pad is touched, a signal is
completed through the key unit and passed back to the LSI through P68- P71 to perform the function that was requested.
2. Control Unit
Control unit consists of LSI, reset circuit, indicator circuit, power source circuit, relay circuit, buzzer circuit, synchronizing signal circuit, absolute
humidity sensor circuit and back light circuit.
1) Reset Circuit
This circuit generates a signal which resets the LSI to the initial state when power is supplied.
2) Indicator Circuit
This circuit consists of 25 segments and 4 common electrodes using a Liquid Crystal Display.
3) Power Source Circuit
This circuit generates voltages necessary in the control unit from the AC line voltage.In addition, the synchronizing signal is available in order to
compose a basic standard time in the clock circuit.
4) Relay Circuit
A circuit to drive the magnetron, fan motor, turntable motor and light the oven lamp.
5) Buzzer Circuit
The buzzer is responsive to signals from the LSI to emit audible sounds (key touch sound and completion sound).
6) Synchronizing Signal Circuit
The power source synchronizing signal is available in order to compose a basic standard time in the clockcircuit.It accompanies a very small error
because it works on commercial frequency.
7) 2nd. Interlock Relay Control Switch
A switch to "tell" the LSI if the door is open or closed.
8) Back Light Circuit
A circuit to drive the back light (Light emitting diodesLD1- LD4).

9) Absolute Humidity Sensor Circuit

This circuit detects moisture of the cooking food to allow its automatic cooking.
[2] 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.
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.
Ventilation opening for sensing
9 – 1
Service Manual
Thermistors
Sensing part
Sensing part
(Open vessel)
(Closed vessel)