The Cyber-Spy.Com Usenet Archive Feeds Directly From The Open And Publicly Available Newsgroup Sci.Electronics.Design
This Group And Thousands Of Others Are Available On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic, Opinions Or Content Posted To This Or Any Other Newsgroup. This Web Archive Of The Newsgroup And Posts Are For Informational Purposes Only.
Message-ID: <3D973D48.AD85F343@texas.net>
From: John Fields
Organization: Austin Instruments,Inc.
X-Mailer: Mozilla 4.01 [en] (Win95; U)
Newsgroups: sci.electronics.design,sci.electronics.misc
Subject: Re: LCD backlight Dimmer circuit
References:
NNTP-Posting-Date: Sun, 29 Sep 2002 13:21:40 CDT
X-DMCA-Notifications: http://www.giganews.com/info/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.1
Date: Sun, 29 Sep 2002 18:21:40 GMT
Richard Soennichsen wrote:
>
> I need to dim an LCD backlight when an external 12V is applied as a signal.
> 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
---
Assuming your LED supply voltage is 12V and your 12V signal goes to 0V
(or at least a couple of volts below 12V) for full brightness,
+12 +12
| |
| |
E |
12OFF>---[R]---B PNP |
C |
| |
[R] [R]
| |
+-----+
|
[LED]
|
GND
---
John Fields
Professional circuit designer
http://www.austininstruments.com
Go Back To The Cyber-Spy.Com Usenet Web Archive Index Of The sci.electronics.design Newsgroup
|