It's a de-facto standard. I've got catalogs from Epson, Seiko, Sharp, etc, all of which use the pinout that apparently agrees with the O/P's LCD, and, among other things, these all refer to the voltage on pin 3 as negative. I didn't say that no LCD's use a positive contrast bias, nor did I say that no LCD's use a different pinout. I just stated the obvious from looking at the pinouts used by what appears to be a majority of LCD module suppliers.

Nowhere have I stated that there are no LCD's that use positive bias. Nowhere have I said that all LCD's use the same pinout. I simply stated that, from a preponderance of evidence as shown in suppliers' catalogs (even OPTREX) that these are conventional. The one OPTREX LCD that I've got in house uses a negative 5-volt bias, i.e. one has to adjust the contrast pot to the most negative voltage available. The fact that YOU, Erik, prefer the ones with positive bias doesn't change the fact that some use negative bias. If I were to go out and buy LCD's, I'd prefer the single-supply types too. I've even got some that don't require a negative bias, but they generate it on their PCB.

Why are you trying to start another "food fight?" Don't you have enough to do?

RE