Hi all, so i've spent the last few evenings wiring up a 16x2 LCD, this is the first time i've tried something like this, so i was a bit wary of it working. Wired it all up to parallel, as it runs off 5v, i thought lets just hack up a USB cable for the 5v and the ground... simple. That all worked well, i got the test signal when i first plugged it in, i loaded up lcd smartie, and selected HD44780, selected 16x2, left it on the default screen of scrolling "Smartie 2.45" or somethign like that... It worked, success, i could see it scrolling away, brilliant, but... it was like the contrast was all out of whack.... each lcd module (square that makes up a letter or digit) was, say, 90% white, and the character being displayed was 100% white, so you could only jsut see it.... I double checked the grounding on pin3. It was wired properly into the 0v line of the USB port like all the other grounds on the LCD... it was all fine I adjusted the contrast slider in LCDSmartie, but nothing changed on the LCD. I disconneted pin 3 incase it was like, backwards, and it was actually max contrast with no connection... but that displayed nothing on the LCD at all, no white, no characters, nothing. So i go to connect the ground back up to pin 3, i do so, but when it comes back on all there is is solid white... no characters or anything now... what happened, did i break it? HELP dragon2309
You need to buy a preset potentiometer and connect its centre pin to pin 3 on the LCD, then its two outside pins to pins 1 and 2 on the LCD. Then you can adjust the preset to set the contrast.
damn, you beat me in my reply to my own thread, i had a brainwave shortly after posting this, and connected up a 4.7k linear pot i had in my components box, contrast is fine now, thanks for the reply
You got yours working, but if anyone else has the contrast pot between 5v and gnd, and the contrast still wont adjust correctly, you may need a negitive voltage, but that is typically for high temperature range LCDs
Oh right, that does sound a little silly, and not entirely logical either... Ah well, good idea still providing the info for future users searching. *EDIT* - NOTE TO SELF: Don't solder +5v lines whent he device is live... In short you get windows shouting at you saying theres power surges on USB hubs, lol, yeh, ell, perhaps not the smartest thign to do... Still works fine though. Windows cut the power to the port, had to reset it.
