Sharp R-231NW Service Manual page 21

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 P52, P53, P54, P55, P56
and P57. When a key pad is touched, a signal is completed
through the key unit and passed back to the LSI through AN2,
AN3, AN4 and 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 and synchronizing sig-
nal circuit.
1) Reset Circuit
This circuit generates a signal which resets the LSI to the ini-
tial state when power is supplied.
2) Indicator Circuit
This circuit consists of 4-digits, 12-segments and 3-common
electrodes using a Liquid Crystal Display.
3) Power Source Circuit
This circuit generates voltage 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
VSS
4) Relay 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 audi-
ble 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 accom-
panies 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.
9 - 1
Application
-5V LSI(IC1)
R-231NW