Character LCD contrast not changing

Other Hardware Displays
1

Hello,

I am working with a JHD539M1 16x4 character LCD and have wired it as such.

1600×1200 218 KB

I have not connected the backlight since that messes up my camera shot, but as you can see the contrast is on full. But it remains that way at every position of the pot. I have checked and the pin 3 is changing voltage from 0 to 5v easily as i change the position of the pot. But for every position the 2nd and 4th lines remain black.

BTW, I am using this tutorial Wiring a Character LCD | Character LCDs | Adafruit Learning System. It says not to go forward without getting the pot to work, hence the question.
(sorry for the lack of colors, will upload new pic in an hour)

2

Hello,

Sorry, let me get my glasses: everything seems to fuzzy.

3

But for every position the 2nd and 4th lines remain black.

Actually your display is upside down as is the display in the Adafruit tutorial until you get a little further on. I guess you already know that since you mention that the 2nd and 4th lines are blank.

Having boxes only on the first and third lines is normal, the question is really 'can you adjust how dark those boxes are'.

Your display appears to be quite normal if the pot is giving you a voltage at or near 0 on pin three. As you raise the voltage the boxes should quickly fade away giving a blank display when you near 5 volts. If your display exhibits that characteristic then everything is OK for you to proceed.

Don

4

Can you let us see how you have it wired.

As said, your display is upside down in the picture we can see and that means that those pins on the left are NOT 1,2,3.

The pins should be at the top right of the display, numbered 1-16, and labelled along the lines of Vss, Vdd, Vo for the supply and contrast.

Can you confirm if these are the pins you're connected to, rather than A,K and D7 at the other end?

5

As said, your display is upside down in the picture we can see and that means that those pins on the left are NOT 1,2,3.

When you visualize the device in the correct orientation the pins are in the more or less normal location, at the upper left. Also, pin 1 is normally near the edge of the display, where his connections are, so that means that he appears to be using the correct pins.

Don