MPGuino lcd help?

[gascort]

I just hooked up my Spiffie Mpguino tonight to the car.
I tested it yesterday using my computer's USB power supply and it worked fine.
Tonight, the screen powers up and I can tell it has text displayed, but something's messed up with the contrast - all the lcd "pixels" are dark, and the actual text pixels are lighter than the rest. It's like the lcd has too much power, and I can't make it low enough to see, like when you replace the batteries in a graphing calculator and you have to adjust it down, but I can't.
I tried flipping through the contrast settings with the center button, but it didn't make them readable.
Did I wire something backwards in order to get the screen to display negative?
I'm going to plug it back in to the computer and see if that way still works.
Any ideas?

[Nevyn]

Couple questions for you (I'll try to help what I can):

You have the kit version, that came with the display?

Each 'character' is a block of 5x8 pixels. Are the blocks black (ON), and the letters white (OFF); or are they just varying levels of on (one black, and the other blackER)?

[gascort]

Originally Posted by Nevyn

You have the kit version, that came with the display?

Each 'character' is a block of 5x8 pixels. Are the blocks black (ON), and the letters white (OFF); or are they just varying levels of on (one black, and the other blackER)?

Yes, I have the kit, and the included display.

The latter; the background of each 'character' is black, and the text is slightly less black. If it were not lit, I would be able to read the negative image, I think.

I tried with the computer USB again; works just fine.
When plugged into the car, I scrolled through the contrast settings. Every 3rd or 4th time the lcd backlight turned off and I just saw solid dark 'characters' across the screen.
Thank you for the help!

[McTimson]

Make sure the voltage regulator is hooked up properly. I had a similar problem, and it turned out to be the voltage regulator wired up backwards. When hooked up to the 5V from the USB, it worked fine, but 12V from the car messed with the voltage too much.

[gascort]

crap... I'm not sure I know what component did that. I'm not new to diodes and resistors and capacitors, but the other 3-4 things on there I just plopped in place and soldered up.
time to look.

BTW, I had my wife plug it in and press buttons on the way home tonight. She said it got stuck on one screen and started smelling hot, so we unplugged it. Hope it still works!

Any advice on how to remove stuff once it's been installed on the MPGuino?

[gascort]

Originally Posted by McTimson

Make sure the voltage regulator is hooked up properly. I had a similar problem, and it turned out to be the voltage regulator wired up backwards. When hooked up to the 5V from the USB, it worked fine, but 12V from the car messed with the voltage too much.

You are a genius. I broke the 7805 off, glued it in place (just to make sure, since it wasn't through the board anymore), re-soldered it, and it works like a charm!
Thanks a lot, bud. Now to log some miles to calibrate!