I am using this LCD:
Plus I am using an Arduino. I am trying to hook this up but without a 10K pot. How is this possible? Every tutorial I found involved the 10K potentiometer
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You could start by using the variable resistor to find the sweet spot for the screen contrast, then use a multimeter to measure the resistance at that point, that should give you a good value for a fixed resistor. Otherwise you could look at using a digital potentiometer chip that could set the screen contrast and could be controlled by the Arduino
I have tried various solutions, those work:
You can connect V0 pin to GND using just a resistor 2k-3k works fine for all LCDs I tested.
You can also control the contrast from your arduino PWM, just connect PWM pin directly to V0 pin and set PWM to between 60 to 120, to prevent flickering you need to change timer prescaler from default 64 to 1 or 8. If you are using pin 3 (timer 2) using this command:
TCCR2B = TCCR2B & 0b11111000 | 0b01;
No other components are necessary.
If you can't change the prescaler and don't like he flickering you can build a low pass filter using a capacitor and a resistor. Connect 10uF capacitor to GND and V0, then connect 470 ohm resistor between PWM pin and V0. Set PWM between 60 and 120
Use potenciometer, you don't need 10k, Just anything above 5k will work fine, Even 1M will work.
I see good reasons for wanting to connect LCD without potentiometer or even fixed resistors at all: when you just want to test a new piece; when you're in hurry, in place lacking anything but wires, or when you just don't want to bother with the question how to connect that resistor so it wasn't fragile, ugly, etc.
If you don't connect that LCD terminal (V0), you don't see anything.
If you connect V0 to GND, you still will be able to see if it works and discern characters (they would be very blurry though, looking from an angle helps).
If you connect V0 to +5V, you don't see anything.
Connecting V0 to GND via 1-1.5K resistor, as mentioned above, gives pretty good contrast.
If you use 5K, you get "inverted" effect (when characters are darker than background, contrast is not ideal in this case though).
I also get the same effect when powering my (enhanced) Arduino and LCD from 3.3V (and putting V0 directly to GND).
My LCD is marked J1602A and is few-bucks from eBay.
The same as leppie's answer, but a 1K resistor to ground. Something in that range should do the trick, depends on the lighting of the environment where you're using it.