3. Automatic Control of LCD ContrastThe control panel controller PCB is equipped with a mechanism capable of auto-matically adjusting the LCD contrast according to changes in temperature.A thermistor (TH911) is mounted on the control panel controller PCB to monitor thetemperature inside the control panel unit. The changes in the resistance of the thermis-tor caused by changes in temperature are used to vary the voltage supplied to the LCDassembly to maintain a specific contrast of the LCD display at all times.The LCD contrast may be varied by adjusting the display contrast knob on the con-trol panel to suit the user`s preference.Figure 7-103If the temperature around the control panel rises, the resistance of the thermistor willlower, thereby increasing the voltage (Vo) supplied to the LCD unit.If the temperature around the control panel lowers, on the other hand, the resistanceof the thermistor rises, thereby decreasing the voltage (Vo) supplied to the LCD unit.OV-24V+5VDC/DCConverterLCD unitThermistor(TH911)VR911VoVo: Voltage supplied to LCD unitCHAPTER 7 EXTERNALS/AUXILIARY MECHANISMS7-4 COPYRIGHT © 1997 CANON INC. CANON NP6560/NP6360/NP6260 REV. 0 NOV. 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
