LCD/Powering question

I'm almost certainly doing something wrong here but I can't find a good answer anywhere. I wired up the LCD and have a row of blocks and an empty row. Nothing I do seems to change what it is displaying.

What's more is that I have to have USB plugged in for it to get power. Just plugging in the 12V power to the RAMPS board doesn't appear to give the rest of the system any power. Ideas?

Sounds like the contrast is set to high/low.

I always add a trim pot on the contrast wiring to make it adjustable. You can read more about it in this thread [forums.reprap.org] as well as a few other threads.

Also if your screen came with J3 soldered over on the back you will need to de-solder it to make it operate correctly.

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I'm having a weird problem with my LCD as well. I wired it up according to the forum post referenced previously but when I plug in the four pin connector to LCD 1 (aux 2 on RAMPS) and plug USB cable in, the arduino does not power up. I simply unplug this four pin connector, leaving everything else alone, and plug USB in and arduino powers up normally. Could this be the result of a short somewhere in my LCD wiring or do I need to change a power setting somewhere? The J3 jumper is not connected on my LCD.

That's definitely indicative of a short. If Sublime doesn't get back to you I'll take pics of mine at home which is working now (won't be until later tonight PST). Definitely check out [forums.reprap.org] as it helped me a bunch. I had to do a little bit of back and forth but I got it sorted.

The only thing other than a short that I can think of is the + and - being backwards. They come out of the ramps in the opposite order than they come out of the LCD so it is easy to get them backwards.

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Thanks maik! I'll take a picture of mine and post it tonight as well to compare.

So... I realized that my ground and 5v wires were flipped on the connector to the RAMPS so I switched those to what they should be and now the display is somewhat working. I can see text but unfortunately no backlight. The trimpot nearest D4, D5, D6 and D7 doesn't change anything when I turn it. My wiring looks like this:

[www.flickr.com]

The white wire in the center is the 5v leading to the left foot of the trimpot on the right side (it's a little unclear in this photograph) and I had to connect it on top as there was no room beneath.

The RAMPS connection looks like this:

[www.flickr.com]

The LCD is a 1602A. I'll keep playing with it, but if anything jumps out to anyone, I'd really appreciate any suggestions you might have. Thanks!

It looks like it is missing the jumper wire between 1, 5 and 16 which will give your backlight a ground and it also holds pin 5 low.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver

Thanks a ton Sublime! After looking at the wiring again, I suspected that but I'm quite new to this so I wasn't sure...

EDIT: Works great now, backlight and all.

Edited 1 time(s). Last edit at 08/22/2013 02:44AM by Nick101.

Good to hear.

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FFF Settings Calculator	Gcode post processors	Geometric Object Deposition Tool Blog
Tantillus.org	Mini Printable Lathe	How NOT to install a Pololu driver