My LCD needs -14V I have connected it to the -12V supply and even with the contrast pot turn fully up I can only just see that the display is on. Bearing in mind that I have only connected the power so far so I don't know what I should expect to see. Is this because the voltage isn't correct or becasue I won't see anything until I connect the parallel cable up and get some s/w running ?
With just power you should just see a row of dark squares, (or light squares if it is inverted) you may need the full -14v to bias it, so check out some dc-dc converters and see if you can find a cheap one.
One easy trick is to take two 9V batteries and wire them with the positive side to ground, and negative side toward your -17V supply (your pot) and then use the middle wiper of the pot to get your contrast voltage.
You haven't said what type of LCD you have. With graphic types, you won't see anything no matter where the contrast pot is set to. With alphanumeric types you will see alternate rows of solid squares.
Sorry it is a graphic so I guess I'll have to get the iron out and wire up the parallel cable before I even know if its working.
