My son and I are new to Arduino and very much enjoying the fun projects. That said, we wired the breadboard for Hello World (and downloaded the Hello World sketch) but the LCD screen is very, very dim - even with the potentiometer's contrast turned to "max". We are using the LCD screen and potentiometer that came with the Arduino UNO kit. I won't post any code as the sketch works, it's just that the LCD screen is dim (at best).
I see no backlight. Pin 15 of the LCD needs to go to ground, I think. In the photo, pin 15 does not seem to be connected to anything.
There may or may not be a current limit resistor installed on the backlight. To be on the safe side you could put a 220 or more resistor from pin 15 to ground.
floresta:
I'm anxiously waiting to hear from Paul__B.
(Inside joke - you'll figure it out when he shows up.)
All right I'll bite!
There are a couple of wiring mistakes here, and my correction to whatever Ky66le was using as a reference.
It was presumably intended that the 1k resistor was to connect from the ground (blue trace) bus - as it presently is - to pin 15 of the LCD module which is indeed at this point, column 9. The resistor presently goes to one end of the potentiometer. So move the resistor over from the potentiometer to column 9 but as per Bill's correction, swap the green and red wires over on pins 15 and 16 of the LCD.
But the end of the potentiometer to which the resistor was connected, should connect to ground. So connect it to ground and all should work.
Now the corrections.
The 1k resistor will give a reasonable backlight brightness. If you want it brighter, check resistor "R8" on the back of the LCD display. It will almost certainly be "101" which is 100 Ohms. It is vaguely possible that "R9" is 100 Ohms instead and "R8" is zero. Now if one or other is in fact, 100 Ohms, then this is already limiting the backlight current and for maximum brightness, you can connect pin 15 16 of the LCD directly to ground without the 1k resistor.
Secondly, connecting one end of the potentiometer to 5 V is a longstanding mistake in the designs that people unknowingly copy from one amateur project to another. Do not connect the potentiometer to 5 V, connect one end to ground and if it is a 10k potentiometer, you can actually connect both ends to ground. This will make it a lot easier to adjust the contrast on the LCD (not to be confused with controlling the brightness of the backlight).
The backlight is not working, it is the negative blue STN lcd, it is necessary work with backlight, input 3V or 5V to the backlight (it is up to the datasheet) between pin 15 and pin 16, do not over drive the backlight voltage, otherwise the backlight would be burned soon.
kathy166:
The backlight is not working, it is the negative blue STN lcd, it is necessary work with backlight, input 3V or 5V to the backlight (it is up to the datasheet) between pin 15 and pin 16, do not over drive the backlight voltage, otherwise the backlight would be burned soon.
Correct, but also in order for it to work, power and ground must be connected properly.
i.e. It will not work when the backlight power connections are wired up backwards.
