Hello.
I just wonder if i can use a higer value potmeter than 10K on the contrast ?
i have broken the one i have , and have only 100K and 1k left , but dont want to use 1k
I don’t see why not. You will have to turn it a lot slower and it will get really dim before you reach the stop on the pot…
I’ve always found that the contrast pots have lousy range when wired to ground and 5V.
I find that wiring them 2 terminal style from the contrast pin to ground works out better.
Yes, you need a 10K because there are 5 resistors that are on the PCB with the Hitachi chips.
The value of your pot is determined by that.
Yes, you need a 10K because there are 5 resistors that are on the PCB with the Hitachi chips.Yes, you need a 10K because there are 5 resistors that are on the PCB with the Hitachi chips.
What makes you say that? There is only one resistor (variable) for the contrast. You don’t even need a pot. You can use a couple of resistors in replacement of the pot…
You could use a fixed resistor, but those LCDs are very sensitive to temperature, supply voltage and viewing angle.
That’s why many devices have either a front panel pot or software control of the contrast.
Check out the [Hitachi HD44780U spec sheet.
The driving waveforms for the LCD come from a ladder of resistors using up to 6 different voltage levels.
Hitachi does not specify anywhere what value to use for the 5 resistors.
The value is chosen by the LCD makers who use the Hitachi controller.
I measured a board once and it was 2.2K for each resistor.
The board came with an external 10K trimmer thrown in.
By adjusting this between the extremes of conceivably useful values I came up with a range.
A 2.5K trimmer would work better covering the range.
Note: This is all using the trimmer as a variable resistance to ground (no Vcc connection).](https://www.sparkfun.com/datasheets/LCD/HD44780.pdf)