Problems with LCD

So I just recieved a new package with electronic components. But I am having trouble with PC 1602-H (16x2 LCD). The characters that are displayed are very hard to see (if I turn off the backlight I can't see anything). I connected everything as allways (this is not my first LCD) and double checked with schematic in the playground. I turned the contrast adjustment trimmer all the way I can and only then I can see something (what is displayed is correct) but just barely. Which is strange since I am using a 10k-ohm trimmer.

Another strange thing that while I was playing with the wires (GND and +5V on arduino) the display came to normal contrast for a few seconds and then went back. Any ideas with what is wrong?

I am using Arduino Duemilanove with Atmega8 (I replaced the 168 with 8 because that one died).

I have one LCD that's also hard to see without a backlight. I realized it's probably for outdoor use only. When I took it together with a temperature circuit on a breadboard outside in the sun, it became easier to read.

Besides, your LCD may be designed to be read at an angle. Try look at it at different tilt angles and adjust it.

I don't think that that is the case. Because then the contrast adjustment would have to be on the max (or min ;D) to actualy see anything. And as I said it worked like it should for a few seconds.

Can you provide a datasheet for the LCD in question? Or a link to a product page for it at the vendor you got it from?

Can you post a schematic and your code?

Here is the product page and there is also a link to a datasheet in the bottom (which is realy bad). Here is a link to another (important) part of the datasheet:

Code and the schematic is the same as used here:

EDIT: Strange thing. Sometimes if I pull the ground and connect it again I get random characters that are normaly visible.

EDIT2: Did a little more research. It uses the ST7066U controller. Datasheet here:

Found my problem:

The reason you require a minus voltage with the "H" suffix lcd's, is the fact that they are rated for higher temperatures. The other model numbers work fine with just gnd and 5V. Been using Powertip lcd's since I discovered pics, quite happy with them. But I did have the same problem once, fortunately my vendor is quite clued up, and pointed out the difference.

Picked up a hair dryer and attacked the LCD with it :P. And yes suddenly the characters were visible. So now the only way to get a normal display is to heat it or somehow get negative voltage. Any ideas how to do that?

Just did a little fast test - connected a 1.5V (+ to GND and - to contrast adjust) and .... the whole thing works- or it did until the trimmer started producing smoke. But anyway back to important questions - how to produce negative voltage without some complicated circuits or ICs?