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hardware control of 634 brightness

wellfooled

New member
As I'm using the 634 LCD in an embedded system, there is no keyboard/mouse, meaning no easy s/w adjustment of brightness. Is it possible for me to safely install a potentiometer through either the backlight's 5V or the GRD to control the brightness manually? If so, any recommendations on ohms, wattages?
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CF Tech

Administrator
The 634's backlight is rated at 525mA to 650mA.

The "A" pin connects directly to "+5v(LED)" of J2.

The K pin is connected through R10||R12 through Q1 to ground.

The easiest way would be to vary the voltage on "+5v(LED)" down from +5v.

You could combine this with a "maximum brightness" by setting the backlight brightness and storing it in the EEPROM.

Probably a 5W 100 ohm pot would work fine, Digi-Key CT2154 for example.
 
USB LCD Displays - Graphic and Character LCDs with a Keypad
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