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From: "Helmut Sennewald"
Subject: Re: LCD backlight Dimmer circuit
Date: Sun, 29 Sep 2002 03:25:18 +0200
X-Newsreader: Microsoft Outlook Express 6.00.2800.1106
"Richard Soennichsen" schrieb im Newsbeitrag
> I need to dim an LCD backlight when an external 12V is applied as a
> I have come up with many circuits that brighten the backlight but cannot
> find that "elegant" solution for dimming. The backlight can be considered
> an LED with a fixed resitor. The circuit has to effectively lower the
> voltage to the resistor or perhaps bypass the resistor and supply a lower
> voltage. Both low and high sides are available. Anyone? Thanks
sometimes ago I designed this circuit.
It uses a LDR(light dependant resistor) to control the backlght
depending on the ambient light. If it is darker, the backlight
intensity(current) is reduced.
The description of the circuit is in the middle of this page:
R1(P2) set the max. current. P3 trimmed for minimum brightness.
P1 shifts the sensitivity. P2 is for contrast.
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