MULTIPLEXED_BRIGHTNESS_CONTROL

Published:2009/7/1 22:03:00 Author:May | From:SeekIC

Developed for use with single-chip digital clocks in which several displays are multiplexed. Provides automatic brightness control by using variable duty cycle and switching it on and off in synchronism with display of time. Uses 555 timer in monostable mode, triggered by multiplex oscillator to determine off time of display.When ambient light is bright, resistance of ORP12 photocell is low and display is on most of time. Set 470K pot to give low light output without mistriggering under dark conditions.Timer can also drive decimal point directly and give matched brightness.-M. G. Martin, Automatic Display-Brightness Control, Wireless World, April 1976, p 61.



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