Hmmm that might be a dumb question but is it possible to remove the pot on a HD44780 LCD screen and put a resistor instead?
Hmmm that might be a dumb question but is it possible to remove the pot on a HD44780 LCD screen and put a resistor instead?
It's possible, but why. Lighting conditions change. Power levels change. Being able to adjust the brightness is usually a good thing.
edit: actually ---> what pluggy said.
I have a HD44780 running fine with 2 resistors as a voltage divider (which is what the pot is in reality) after I measured an actual pots setting when I had it working. A 1k and a 4k7 worked for me so the LCD received ~1 volt, your mileage will probably vary.......
PaulS:
Hmmm that might be a dumb question but is it possible to remove the pot on a HD44780 LCD screen and put a resistor instead?
It's possible, but why. Lighting conditions change. Power levels change. Being able to adjust the brightness is usually a good thing.
After the flak you give some noobs Paul 
, I would think you'd a least read the title. (Its for contrast, not brightness, it only tends to work at one setting).
After the flak you give some noobs Paul smiley-wink , I would think you'd a least read the title. (Its for contrast, not brightness, it only tends to work at one setting).
I did read the title. On my LCD, I need to fiddle with brightness and contrast. Yes, the range of resistances for contrast is relatively small, but trim pots are not much bigger than a pair of resistors. If space is a concern, a big pot is not necessary, and the adjustability is retained.
I only had a big pot available for testing and I was too cheap to buy a small one......
It does need to be a pair of resistors in the case of the contrast setting.
PaulS:
Hmmm that might be a dumb question but is it possible to remove the pot on a HD44780 LCD screen and put a resistor instead?
It's possible, but why. Lighting conditions change. Power levels change. Being able to adjust the brightness is usually a good thing.
Because I have it turned all the way down already so there isn't much point in my circuit I guess? (correct me if I'm wrong, I only know so much about electronics)
You can use a led and resistor on 1 pin to read ambient light and adjust your LCD automatically. You can even use the same led to provide light and have it seem to adjust itself. So no, you don't need no stinking turn pot and yet still your LCD be as bright as it should.
GoForSmoke:
You can use a led and resistor on 1 pin to read ambient light and adjust your LCD automatically. You can even use the same led to provide light and have it seem to adjust itself. So no, you don't need no stinking turn pot and yet still your LCD be as bright as it should.
A LED? You mean a light sensor?
A led is also a light sensor. 
pretty much any semiconductor is light sensitive (cut open a big can type transistor one day) but to what degree of usefulness and speed is widely varied
Because I have it turned all the way down already so there isn't much point in my circuit I guess? (correct me if I'm wrong, I only know so much about electronics)
If your LCD works well with the potentiometer turned all the way down then you don't need any resistors at all. Just connect pin 3 to GND.
Don
Then take it into a place that's not as brightly lit.
Then take it into a place that's not as brightly lit.
If you are implying that my answer only applies to dimly lit situations then you are wrong. If his LCD works acceptably with 0 Volts applied to pin 3 via a potentiometer then it will also work with 0 Volts applied to pin 3 via a jumper to ground. I know this for a fact, I have been doing it for more than 20 years with my displays.
Don
Yes, electrically it "works".
However the human eye has this tendency to open up more in darker settings than in brighter ones. A light-emitting display that is comfortable to the eyes in a bright setting will not be as comfortable in a darker setting to normal human beings. To that end it is good to be able to adjust the brightness of the display for viewer comfort. It is also good from a battery-saving viewpoint.
Background & Objective: This project began as an effort to create a smart backlighting system for television remote controls. A low-power capacitive proximity sensor detects active handling which in turn controls the backlight. To save battery life, the backlight should not be turned on in bright conditions. But adding a separate light sensor would require a new mechanical design for the remote, adding considerable cost. Our solution was to use the backlight LED itself as the light sensor. We developed a simple microprocessor interface technique that uses one additional digital I/O pin, but no other additional components compared to those need to simply light the LED. Since the circuit draws only microwatts of power, it has a minimal impact on battery life.
Hmmmm, and for their purposes it's better to shut the backlight off in bright conditions.
To that end it is good to be able to adjust the brightness of the display for viewer comfort.
According to the original post and according to the topic heading this thread is about the contrast and not about the brightness.
You have an unattributed quote in your previous post which has nothing to do with this thread.
Don
EDIT: I found it - your quote is from one of your unexplained and irrelevant links in Reply # 12.
floresta:
To that end it is good to be able to adjust the brightness of the display for viewer comfort.
According to the original post and according to the topic heading this thread is about the contrast and not about the brightness.
You have an unattributed quote in your previous post which has nothing to do with this thread.
Don
EDIT: I found it - your quote is from one of your unexplained and irrelevant links in Reply # 12.
In Your Rather Pedantic Opinion.
hpf777:
I hope you have found your answer among all the smoke. It is in replies 3 and 13.
Don