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Simple negative voltage generator (up to -16V)
http://forum.lcdinfo.com/viewtopic.php?f=6&t=659
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Author:  mihneavoda [ Mon May 17, 2004 15:38 ]
Post subject:  Simple negative voltage generator (up to -16V)

Last week I needed help with Powertip PG128128A LCD but nobody bothered to answer for about three days.Anyway, the problem was the contrast voltage which had to be around -12V.So...I made a lightly modified charge pump.It has an output of about -16V from a +5V input, a maximum current of 10mA (beyond this point voltage drops significantly) and fits on a piece of 6*4cm of test board.Anyone having problems with the contrast circuit feel free to use this schematic.R3 is a 10k pot for manual contrast adjustment.
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Author:  Henri [ Tue May 18, 2004 18:03 ]
Post subject:  Re: Simple negative voltage generator (up to -16V)

Thanks for the schematic.

mihneavoda wrote:
Last week I needed help with Powertip PG128128A LCD but nobody bothered to answer for about three days.

Did you ask about it in this forum ? I just tried to look around but didn't see anything like that.
Anyway it's not that strange in a forum like this that you won't get answer immediately. I for example haven't had time to be here in the last four days. Sometimes posts can be also missed and then noticed weeks later...
But looks like you solved your problem yourself :)

Author:  csaba911 [ Sun Jun 13, 2004 9:03 ]
Post subject:  -8 Volt up to 2mA

Here is a very simple circuit I made up from leftover parts.
Using a SMD RS232 driver and a few CAP form a dead CD-ROM.

The output will drop to 4 volt at 1.5mA, but for my lcd all I need is -3v 1.5mA.

Maybe some one can use it.!!

STEVE


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Author:  croc4 [ Sat Nov 13, 2004 2:58 ]
Post subject: 

what is the value of the caps you used?

Author:  csaba911 [ Fri Oct 07, 2005 7:33 ]
Post subject: 

2.2uf

Author:  Clyff [ Mon May 23, 2011 12:54 ]
Post subject:  Re: Simple negative voltage generator (up to -16V)

the scheme is detailed:) it's great
extracting audio from YouTube

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