R-741M (serv.man2) - Sharp Home Appliance Service Manual (repair manual). Page 7

7

741M -

OUTLINE OF TOUCH CONTROL PANEL

The touch control section consists of the following circuits as
shown in the touch control panel circuit.

The principal functions of these circuits and their related
signals are explained below.

Signals generated in the LSI are sent to the tact switches
through SEG0, SEG1, SEG2, and SEG3.
When a tact switch is touched, a signal is completed through
the tact switch and passed back to the LSI through P20 and
P23 to perform the function that was requested.

Control unit consists of LSI, ACL circuit, indicator circuit,
power source circuit, relay circuit, buzzer circuit, synchroniz-
ing signal circuit and back light circuit.

This LSI controls the tact switch strobe signal, relay
driving signal for oven function and indicator signal.

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

This circuit consists of 4-digits, 12-segments and 3-
common electrodes using a Liquid Crystal Display.

This circuit generates voltage necessary in the control
unit from the AC line voltage.

Symbol

Voltage

Application

VC

- 5V

LSI(IC1)

To drive the magnetron, grill heater, fan motor, turntable
motor and  light the oven lamp.

The buzzer is responsive to signals from the LSI to emit
audible sounds (tact switch 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
LED1-LED4)