R990K(W)
9 – 1
R990K(W)
Service Manual
CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY
[1] OUTLINE OF TOUCH CONTROL PANEL
The touch control section consists of the following units as shown in
the touch control panel circuit.
(1) Key Unit (2) Control Unit
The principal functions of these units and their related signals 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 P10-P17.When a key pad is touched, a
signal is completed through the key unit and passed back to the LSI
through R24-R27to perform the function that was requested.
2. Control Unit
Control unit consists of LSI, power source circuit, synchronizing signal
circuit, ACL circuit, buzzer circuit, temperature measurement circuit,
absolute humidity sensor circuit and indicator circuit.
1) LSI
This LSI controls the temperature measurement signal, AH sensor
signal, key strobe signal, relay driving signal for oven function and
indicator signal.
2) Power Source Circuit
This circuit generates the voltages necessary for the control unit
from the AC line voltage.
3) Synchronizing Signal Circuit
The power source synchronizing signal is available in order to com-
pose a basic standard time in the clock circuit. It incorporates a
very small error because it works on commercial frequency.
4) ACL Circuit
A circuit to generate a signals which resetting the LSI to the initial
state when power is applied.
5) Buzzer Circuit
The buzzer is responds to signals from the LSI to emit noticing
sounds (key touch sound and completion sound).
6) Temperature Measurement Circuit: (OVENTHERMISTOR)
The temperature in the oven cavity is sensed by the thermistor. The
variation of resistance according to sensed temperature is detected
by the temperature measurement circuit and the result applied to
LSI. The LSI uses this information to control the relay and display
units.
7) Absolute Humidity Sensor Circuit
This circuit detects the humidity of a food which is being cooked, to
control its automatic cooking.
8) Stop Switch
A switch to inform the LSI if the door is open or closed.
9) Relay Circuit
To drive the magnetron, heating element, fan motor, convection
motor, damper motor, turntable motor and light the oven lamp.
10)Indicator Circuit
Indicator element is a Fluorescent Display.Basically, a Fluorescent
Display is triode having a cathode, a grid and an anode. Usually,
the cathode of a Fluorescent Display is directly heated and the fila-
ment serves as cathode.The Fluorescent Display has 8-digits, 16-
segments are used for displaying figures.
[2] DESCRIPTION OF LSI
The I/O signal of the LSI (IZA840DR) are detailed in the following table.
Pin No. Signal I/O Description
1 VCC IN Connected to GND.
2 VEE IN
Anode (segment) of Fluorescent Display light-up voltage: -30V.
Vp voltage of power source circuit input.
3 AVSS IN
Power source voltage: -5V.
VC voltage of power source circuit input.
4VREFIN
Reference voltage input terminal.
A reference voltage applied to the A/D converter in the LSI. Connected to GND.(0V)
5AN7IN
Used for initial balancing of the bridge circuit (absolute humidity sensor). This input is an analog input terminal
from the AH sensor circuit, and connected to the A/D coverter built into the LSI.
6AN6IN
AH sensor input.
This input is an analog input terminal from the AH sensor circuit, and connected to the A/D converter built into
the LSI.
7-9 AN5-AN3 IN Heating constant compensation terminal.
10 AN2 IN
Input signal which communicates the door open/close information to LSI.
Door closed; "H" level signal(0V).
Door opened; "L" level signal(-5V).
11 AN1 IN
Input signal which communicates the damper open/close information to LSI.
Damper opened; "H" level signal(0V:GND).
Damper closed; "L" level signal(-5V).
12 AN0 IN
Temperature measurement input: OVEN THERMISTOR.
By inputting DC voltage corresponding to the temperature detected by the thermistor, this input is converted
into temperature by the A/D converter built into the LSI.
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