Touch Control Panel - Sharp R-4H56 Service Manual

R-4H56
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 the signals com-
municated among them are explained below.
Key Unit
The key unit is composed of a matrix, signals generated in
the LSI are sent to the key unit through B2,B3,B5, B6,B7,G0
and G1. When a key pad is touched, a signal is completed
through the key unit and passed back to the LSI through H0
- H3 to perform the function that was requested.
Control U nit
Control; unit consists of LSI, power source circuit, synchro-
nizing signal circuit, ACL circuit, buzzer circuit, temperature
measurement circuit, reheat sensor circuit and indicator
circuit.
1) LSI
This LSI controls the temperature measurement signal,
reheat sensor signal, key strobe signal, relay driving
signal for oven function and indicator signal.
2) Power Source Circuit
This circuit generates voltage necessary in the control
unit.
Symbol Voltage
VC -5.2V
VP -25V
VF1 3Vac
VF2
TOUCH CONTROL PANEL ASSEMBLY
OUTLINE OF TOIUCH CONTROL PANEL
Application
LSI(IC1), ACL circuit
Fluorescent display tube : Grid
and anode voltage
Filament of fluorescent display
tube
(VF1 to VF2 voltage)
3) 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.
4) ACL Circuit
A circuit to generate a signal which resets the LSI to the
initial state when power is supplied.
5) Buzzer Circuit
The buzzer is responds to signals from the LSI to emit
noticing sounds (key touch sound and completion sound).
6) Reheat Sensor Circuit
This circuit detects moisture of a food which is cooking
to allow its automatic cooking.
7) Stop Switch
A switch to "tell" the LSI if the door is open or closed.
8) Relay Circuit
To drive the magnetron, fan motor, turntable motor and
light the oven lamp.
9) Indicator Circuit
Indicator element is a Fluorescent Display.
Basically, a Fluorescent Display is triode having a
cathode, a grid and an anode. Usually, the cathode of a
Fluorescent Display is directly heated and the filament
serves as cathode.
The Fluorescent Display has 6-digits, 13-segments are
used for displaying figures.
10) Weight Sensor Circuit
The circuit measures the weight of food by piezo-electric
device.
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