Sharp R-204EWA Service Manual - Page 20

R-204EWA TOUCH CONTROL PANEL ASSEMBLY 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. Key Unit The key unit is composed of a matrix, signals generated in the LSI are sent to the key unit through R00, R01, R03, R20 and R21. When a key pad is touched, a signal is completed through the key unit and passed back to the LSI through R23, K00, K01 and K02 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 and synchronizing signal 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 4-digits, 12-segments and 3common 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 VC Voltage Application -5V LSI(IC1) 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 audible 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 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. 18