Xem Posted June 9, 2009 Report Share Posted June 9, 2009 hello.. i wired my lcd and i works very well..but the backlight get so hot.. i verified the problem.. i noticed that the P1 should regulate the current on it..turning it do not change the lum of the led.. the volts at the a-k is always the same (5,2v)Is this normal? what should i do?--ps.. wops.. i forgot to say what i'm speaking about.. the project o built is the mb-6582 Quote Link to comment Share on other sites More sharing options...
Wilba Posted June 10, 2009 Report Share Posted June 10, 2009 Post a link to where you got the LCD, or a datasheet, etc.It's possible it's an edge-lit backlight and needs much less current than what the Core module provides. Quote Link to comment Share on other sites More sharing options...
Xem Posted June 10, 2009 Author Report Share Posted June 10, 2009 http://docs-europe.electrocomponents.com/webdocs/06dd/0900766b806dda1c.pdf Quote Link to comment Share on other sites More sharing options...
Wilba Posted June 10, 2009 Report Share Posted June 10, 2009 OK, I have this exact model (with low-power amber LED backlight).See page 3.Only the "yellow-green" LED backlight model has a current draw of around 280mA, all the others only have a single LED on the side and draw much less, 20-25mA. Therefore it's likely you are supplying this LED with too much current. Luckily, these models are quite easy to replace the LED, if you have to.To reduce the current supplied by the Core backlight circuit (in this case MB-6582), insert a 47K resistor in series with R4 (either between R4 and T1 or between R4 and P1). See attachment. Quote Link to comment Share on other sites More sharing options...
Xem Posted June 10, 2009 Author Report Share Posted June 10, 2009 i'll replace R4 whit that resistor.. thank you..the led was on for less then 1 minute.. i hope it has not get damaged Quote Link to comment Share on other sites More sharing options...
Wilba Posted June 10, 2009 Report Share Posted June 10, 2009 Note, do not REPLACE, you ADD this 47K resistor. Quote Link to comment Share on other sites More sharing options...
Xem Posted June 11, 2009 Author Report Share Posted June 11, 2009 why? is it so different 47k or 48k? Quote Link to comment Share on other sites More sharing options...
Wilba Posted June 11, 2009 Report Share Posted June 11, 2009 Adding instead of replacing lets you short it out if you change your LCD and go back to just R4 of 1K. It also means you don't have to desolder the resistor and potentially damage the pads.But you are right, 47K or 48K won't have much difference. Quote Link to comment Share on other sites More sharing options...
Xem Posted August 26, 2009 Author Report Share Posted August 26, 2009 hello, do you remember this topic?so.. i started to use my mb6582, yesterday the backlight of the lcd id dead..i tested the volt on the led and i have 5 volt..=(do you have any idea? i remember that noting was getting hot anymore... Quote Link to comment Share on other sites More sharing options...
Wilba Posted August 27, 2009 Report Share Posted August 27, 2009 I think the LED was still getting too much current.I've done some more tests with this display and I think R4 needs to be more like 80K to limit LED current to 25mA.With around 47K the LED was probably getting 40mA-50mA which will eventually burn out a LED over time.I'm sorry I suggested the wrong value... I was using 47K myself thinking it was OK, but a real test with a current meter proves this resistor is too small a value.I have one of these displays with low-power amber LED backlight if you're interested, I can sell it to you VERY cheap. The LED can be replaced with another colour LED, if you prefer white, for example. Quote Link to comment Share on other sites More sharing options...
Xem Posted August 27, 2009 Author Report Share Posted August 27, 2009 umh.. no problem.. i'll try to replace it and then i'll tell you if i want the display.. Quote Link to comment Share on other sites More sharing options...
Xem Posted September 28, 2009 Author Report Share Posted September 28, 2009 just to let know.. i replaced the led.. it was easy.. è now throw it are flowing 0.02 mA, and it seems right.. Quote Link to comment Share on other sites More sharing options...
Wilba Posted September 29, 2009 Report Share Posted September 29, 2009 Good to hear, Xem! Quote Link to comment Share on other sites More sharing options...
GuitarNut Posted February 10, 2011 Report Share Posted February 10, 2011 I think the LED was still getting too much current. I've done some more tests with this display and I think R4 needs to be more like 80K to limit LED current to 25mA. With around 47K the LED was probably getting 40mA-50mA which will eventually burn out a LED over time. I'm sorry I suggested the wrong value... I was using 47K myself thinking it was OK, but a real test with a current meter proves this resistor is too small a value. I have one of these displays with low-power amber LED backlight if you're interested, I can sell it to you VERY cheap. The LED can be replaced with another colour LED, if you prefer white, for example. I have a similar problem, unknown LCD no datasheet. LCD works but Backlight trimpot has no effect (full on all the time) I Like the "adding resistor to calm it down" idea. It seems like adding the resistor to the side of the LCD light would be easier and I wouldnt be damaging my cores traces. The back of the LCD LED connectors show "K" and "A" which one would I put the resistor on? Thanks for any help This was my first post GuitarNut Quote Link to comment Share on other sites More sharing options...
nILS Posted February 10, 2011 Report Share Posted February 10, 2011 The back of the LCD LED connectors show "K" and "A" which one would I put the resistor on? Doesn't matter. Quote Link to comment Share on other sites More sharing options...
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