ADMIN EDIT: If you're not familiar working with mains power don't even consider this option, please. Anyway in some situations this can be a good option.
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There are many ways to get -8v for the LCD display. Some ppl use the computer PSU (-12v and a pot), some use a charge pump (expensive and complicated).
A simple way that worked for me was to use a mains transformer (2 tailed), a bridge recitfier, a +5v volatge reulator (LM7805) and a -9v volatage regulator(LM7909). You will also need some caps to smooth out the voltages a bit. All easily accessible from any good electronics shop.
The 2 talied transformer has two 12vAC leads and a ground(0v). Connect the 2 12vAC lead to the AC pins on the bridge rectifier. Using the 0v from the tranformer you should now have +12 and -12v between the 0v and the + and - pins on the rectifier respectively.
Use some caps (about 1000uF) to smooth out voltages as they will be unipolar sine waves from the recifier ( ie. vvvvv as opposed to ------- if you get what I mean).
Now use the +5 voltage reg on the +ve side (ie input from rectifier, GND from transformer, and output will be +5v) and -9v regulator on the -ve side (ie input from -ve side, GND from transformer, and output will be -9v).
This should now give you very smooth +5v, and -9v.
Use a pot to adjust the -9v for the display.
Worked a treat for me and much cheaper than charge pump and no risk of killing my hard drives or motherboard.
Good luck.
P.S. If you have no idea what a bridge rectifier is or how a voltage regulator works then you shouldn't be trying to make your own LCD display!! Quickly unplug your soldering iron and put it in a safe place where you will never be able to find it again. And don't plain with mains power.
Here is an ASCII picture....cut and paste and change to fixed pitch font (e.g. courier) to see the pic properly:
Code:
--- --12vAC---------------/\~
)( / \
)( / \
240)( /bridge\
AC ) ---0v----+ -< rect'r >+
or )( | | \ / |
110)( | | \ / |
AC )( | | \ / |
--- --12vAC--)-------)----\/~ |
| | |
| | |
0V -12V +12V
| | |
+--+||--+----------)---- -12v--[LM7909]---------> -9v
| 1000uF | |
+----------||+-----+---- +12v-----)---[LM7805]--> +5v
| 1000uF | |
+----------------------- 0v ------+-------+-----> GND
)( / \
)( / \
240)( /bridge\
AC ) ---0v----+ -< rect'r >+
or )( | | \ / |
110)( | | \ / |
AC )( | | \ / |
--- --12vAC--)-------)----\/~ |
| | |
| | |
0V -12V +12V
| | |
+--+||--+----------)---- -12v--[LM7909]---------> -9v
| 1000uF | |
+----------||+-----+---- +12v-----)---[LM7805]--> +5v
| 1000uF | |
+----------------------- 0v ------+-------+-----> GND
Hope this works for you. And usual disclaimer: anything goes wrong or you kill you LCD or yourself it is NOT my fault.
You may need some sort of heat sink.
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