Mr modnaR Posted August 13, 2006 Report Share Posted August 13, 2006 hello all, i've just returned from my holiday to find a lovely package waiting to be torn open and the contents constructed! ;Dnow, the problem is: i've made up the first core, and it works fine, i've uploaded MIOS and the SID application, however, i cannot adjust the backlight with the left hand pot. the other adjusts the contrast just fine. what can i have done wrong? i have checked the pins of the pot with my multi meter, but there is no voltage any direction. any ideas? thanks.also an unrelated (i think) problem, i have an lcd from SmashTV which works fine (apart from the backlight being on full power). however i also have an LCD from crystalfontz, but that backlight does not work at all. i applied the backlight voltage in reverse, and it worked! is this unrelated to the adjustment problem, or could it be related?cheers in advance. Quote Link to comment Share on other sites More sharing options...
Altitude Posted August 13, 2006 Report Share Posted August 13, 2006 the brightness pot does work, but on my LCDs, it barely registers (this is true for the smash LCD) Quote Link to comment Share on other sites More sharing options...
TK. Posted August 13, 2006 Report Share Posted August 13, 2006 Maybe it works better with a 50k pot instead of a 10k pot, could somebody try this out?i applied the backlight voltage in reverse, and it worked! is this unrelated to the adjustment problem, or could it be related?The backlight has a polarity, it's a LED - therefore this is not relatedBest Regards, Thorsten. Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted August 13, 2006 Author Report Share Posted August 13, 2006 the brightness pot does work, but on my LCDs, it barely registers (this is true for the smash LCD)i measured the output to the LCD though (B+ and B-) and there was no change in voltage. strange. Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted August 13, 2006 Author Report Share Posted August 13, 2006 Maybe it works better with a 50k pot instead of a 10k pot, could somebody try this out?i'll try this out.The backlight has a polarity, it's a LED - therefore this is not relatedBest Regards, Thorsten.yes i understand this, i just couldn't understand why they would be different if they both are compatible with the hitachi standard. i guess it's just the other pins that have to comply, not the backlight. ah well, i'll just have to switch them round. Quote Link to comment Share on other sites More sharing options...
Jaicen Posted August 14, 2006 Report Share Posted August 14, 2006 You won't register a change in voltage with the brightness control, it's acting as a current limiter. LED's don't really respond well to changes in voltage, more current usually = more brightness. As TK said, i'd put in a bigger pot, maybe get hold of a 100K multi-turn pot, i'm sure that'll solve your problem. Quote Link to comment Share on other sites More sharing options...
stryd_one Posted August 14, 2006 Report Share Posted August 14, 2006 Yeh the HD44780 standard does not include the backlight, that's left up to the manufacturer - although I never could figure out why they use strange voltages sometimes ??? Quote Link to comment Share on other sites More sharing options...
Mr modnaR Posted August 14, 2006 Author Report Share Posted August 14, 2006 You won't register a change in voltage with the brightness control, it's acting as a current limiter. LED's don't really respond well to changes in voltage, more current usually = more brightness. As TK said, i'd put in a bigger pot, maybe get hold of a 100K multi-turn pot, i'm sure that'll solve your problem. ahh i see. thanks for the tip. Quote Link to comment Share on other sites More sharing options...
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