R-891M - Sharp Home Appliance Service Manual (repair manual). Page 8

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891M -

OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following units.

(1) Switch Unit
(2) Control Unit (The Control Unit consists of Power

Unit and Display Unit).

The principal functions of these units and the signals
communicated among them are explained below.

Switch Unit
The switch unit is composed of a matrix, signals
generated in the LSI are sent to the switch unit through
P41, P42, P43 and P44.
When a switch button is touched, a signal is completed
through the switch unit and passed back to the LSI
through P91, P93, P94, P95 and P40 to perform the
function that was requested.

Control Unit
Control unit consists of LSI, IC, ACL circuit, indicator
circuit, LCD driver, power source circuit, relay circuit,
buzzer circuit, synchronizing signal circuit, switch unit
circuit and back light circuit.

This is a microcomputer, responsible for controlling
the entire control unit.

This is a read only memory IC, responsible for giving
IC1 the all programmes.

This is a memory IC.
This memorizes the contrast of LCD.

This is an amplifier IC.
This IC controls the contrast of LCD signal.

This IC drives the LCD.

This IC generates a signal which resets the LSI to
the initial state when power is supplied.

This circuit consists of 100 x 65 dots using a Liquid
Crystal Display.

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

-5.0V

LSI(IC1)

A circuit to drive the magnetron, fan motor, turntable
motor, convec. motor, heater and  light the oven
lamp.

The buzzer is responsive to signals from the LSI to
emit audible sounds (key touch sound and
completion sound).

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.

A switch to “tell” the LSI if the door is open or closed.

A circuit to drive the back light (Light emitting diodes
LD1- LD6 and Lamps LMP1, LMP2).

The switch circuit is composed of a matrix, signals
generated in the LSI are sent to the switch circuit
through PB6, PB7, P91, P93, P94, P95 and P40.
When a switch button is touched, a signal is
completed through the switch circuit and passed
back to the LSI through P41, P42, P43 and P44.

The temperature in the oven cavity is sensed by the
thermistor.
Tte variation of resistance according to sensed
temperature is detected by the temperature
measurement circuit and the result applied to LSI.
The result of detecting is given to LSI controlling the
relay and display.