R-351NW
9 - 1
CHAPTER 9. TOUCH CONTROL PANEL ASSEMBLY
Symbol
Voltage
Application
VSS
-5V
LSI(IC1)
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 clock circuit. It accompanies a
very small error because it works on commercial frequency.
7)
Door Sensing 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 diodes LD1- LD3).
[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 CPU 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 P52 – P57. When a key pad is
touched, a signal is completed through the key unit and passed back to the LSI through AN2 – AN5 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
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 14 segments and 3 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 avail-
able in order to compose a basic standard time in the clock circuit.
[2] SERVICING FOR TOUCH CONTROL PANEL
1. Precautions for Handling Electronic Components
This unit uses CMOS LSI in the integral part of the circuits. When handling these parts, the following precautions should be strictly
followed. CMOS LSI have extremely high impedance at its input and output terminals. For this reason, it is easily in
fl
uenced by the
surrounding high voltage power source, static electricity charge in clothes, etc., and sometimes it is not fully protected by the built-in
protection circuit.
In order to protect CMOS LSI.
1) When storing and transporting, thoroughly wrap them in aluminium foil. Also wrap PW boards containing them in aluminium foil.
2) When soldering, ground the technician as shown in the
fi
gure and use grounded soldering iron and work table.
approx. 1M ohm
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