geezer88
Senior Member
I have been playing with a four line LCD that I picked up in a surplus store. It came with no documentation, but an online search of the sticker information turned up this:
http://www.varitronix.com/Product/character/VL-FS-MDLS20464BD-09.pdf
Yep, that's the one. I wired it all up and nothing happened. That's when I wrote up this touch sensor article for debugging:
http://www.picaxeforum.co.uk/showthread.php?t=18295
Using that technique I verified that the code and the Picaxe were working as expected.
Some more online searching found a reference to needing a minus power supply connection to the contrast pin (V0) on some LCDs. Well, applying -3 volts with an auxiliary battery did the trick. All works fine.
Now that is quite inconvenient to need a bipolar power supply, especially for a battery operated application. So the point of this thread is to watch out for surplus devices, or you may find life more complicated than you were expecting. I would also like to know if this need for minus voltage on the contrast pin has been found by other experimenters, or if I was just "lucky"?
tom
http://www.varitronix.com/Product/character/VL-FS-MDLS20464BD-09.pdf
Yep, that's the one. I wired it all up and nothing happened. That's when I wrote up this touch sensor article for debugging:
http://www.picaxeforum.co.uk/showthread.php?t=18295
Using that technique I verified that the code and the Picaxe were working as expected.
Some more online searching found a reference to needing a minus power supply connection to the contrast pin (V0) on some LCDs. Well, applying -3 volts with an auxiliary battery did the trick. All works fine.
Now that is quite inconvenient to need a bipolar power supply, especially for a battery operated application. So the point of this thread is to watch out for surplus devices, or you may find life more complicated than you were expecting. I would also like to know if this need for minus voltage on the contrast pin has been found by other experimenters, or if I was just "lucky"?
tom
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