hd44780lcd
I found tutorial about connecting HD44780 display to Raspberry Pi.
In this tutorial there is no contrast potentiometer. Vo is connected to ground.
Tutorial author says:
In order to control the contrast you can adjust the voltage presented
to Pin 3. This must be between 0 and 5V. I tied this pin to ground.
Is this common and correct way to use this display?
I never seen that before (Vo connected to GND).
I found the problem. The power dissipation of the module was higher than what is written in the data sheet and it caused voltage drop. By using a stronger power supply (LM7805 + TIP2955 ) the contrast is ok now.
Your LCD's LED typically accepts 4.2~4.6V. It should be self regulating, so no further resistor needed. You have 11V or 5V available. Below are the three options available. First is use a Adjustable regulator from 11V. The Second is use a fixed 5V regulator and then a regular silicon Diode (1n4001 or similar) to bring it down another ~0.7V. In either mode, the regulator wastes 1 Watt of heat, a heatsink might be recommended (attach the regulator to the module's metal casing is one method).
Or as mention, tap off the already existing 5V regulator, and just throw on the diode. 0.160A is not exactly a large load, it should be fine.
simulate this circuit – Schematic created using CircuitLab
Best Answer
Yes, it works and quite common. It's 0V to VCC, inclusive. Ground is 0V. So that works. You can also use a pair of resistors to make a voltage divider for a fixed contrast outside of just Ground. Only draw back is that you can't adjust the contrast, but unless you are taking the display to very different lighting environments all the time, who cares.