Page 9
MW24-1100 MICROWAVE OVEN
Theory of Operation
3-4
#814888 - Revision A - May, 2009
Touch Control Panel Assembly
The touch control section consists of the following units:
1.
Key Unit
2.
Control Unit (Control Unit consists of:)
a.
Power Unit
b.
LSI (Large Scale Integration circuit) Unit.
The principal functions of these units and the signals
communicated among them are explained below.
Key Unit
The key unit is composed of a matrix. Signals generat-
ed 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 P14, P15, P16, P17, AIN6 and AIN7 to perform
the function that was requested.
Control Unit
Control unit consists of LSI, ACL circuit, indicator circuit,
power source circuit, relay circuit, buzzer circuit, syn-
chronizing signal circuit, absolute humidity sensor cir-
cuit and back light circuit.
1.
ACL
This circuit generates a signal which resets the
LSI to the initial state when power is supplied.
2.
Indicator Circuit
This circuit consists of 40 segments and 16 com-
mon 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.
Symbol
Voltage
Application
VC
-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 avail-
able 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 LD10- LD15).
9.
Absolute Humidity Sensor Circuit
This circuit detects moisture of the cooking food
to allow its automatic cooking.