hello world lcd without pot

Hi I'm following this tutorial: http://arduino.cc/en/Tutorial/LiquidCrystal and I don't how a pot how can I make the lcd work without one? thanks

you can use a fixed resistor...

Try it with pin 3 connected to GND. Most LCDs work best with about 0.5 volts on pin 3 but many work acceptably with 0 volts. At least you should be able to determine that your setup is working and you can then get a proper potentiometer.

If you have a collection of resistors you can make a fixed voltage divider (the potentiometer gives you a variable voltage divider). Try a resistance around 1K between pin 3 and GND and another around 10K between pin 3 and +5 volts. You want a ratio of about 1:10 between the two resistors and a total resistance between 5K and 20K.

Don

it is a common misunderstanding in these discussions that a potentiometer or voltage divider is required.

There is already an 11k chain (five by 2k2 or “222” SMD resistors) on the LCD board from Ve to Vcc. Paralleling this with another resistor is a complete waste of time and effort (and component). To set about half a volt on Ve, just use a 1k resistor to ground and vary it from there as necessary (compare it to a direct connection to ground to figure whether it needs to be less or more).

The only reason a 10k potentiometer was ever used is that it was presumably on hand when the first person wrote the datasheet which has been blindly copied innumerable times since. As so often happens.

Paul__B, I didn't know that, thanks.

What about PWM output with a RC filter to the Vo ? So it is possible to adjust it with the sketch. That could be useful when the display is used in a cold and a hot environment.

Peter_n:
What about PWM output with a RC filter to the Vo ? So it is possible to adjust it with the sketch. That could be useful when the display is used in a cold and a hot environment.

A very cold and/ or hot environment. That is about the only reason you might have for wanting to adjust what is otherwise a “set and forget” function, otherwise a waste of components and code space. :smiley: