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CFAG12864B-TMI-V Backlight Problem

KE4NYV

New member
I just received one of these graphic LCDs and started to write some PIC code for it. I noticed that when I first hooked it up the backlight was fairly bright, but not alarmingly bright, as to indicate too much voltage. After a day of experimenting, the backlight appears only about half as bright now. I did'nt chnage anything in wiring and it has been tied to 5VDC all along.

Has anyone else seen this? Did I just get a faulty LCD?

Thanks,
Jason.
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CF Tech

Administrator
Connecting it directly to 5v will kill it.

There is some text here on connecting backlights, but you definitely need a dropping resistor. For 5v and 60ma:

RLED = (5v - 3.5v) / 0.060A = 25 ohms
 

KE4NYV

New member
Damn, well theres a first for me and CF LCDs. Never have had one die like that until now with 5VDC.

Just saw your PM, I'll go take care of that now.

Thanks.
 

CF Tech

Administrator
The yellow LEDs should also have a dropping resistor, but they are more tolerant to the abuse of having +5v hooked directly across them.

So if it was a yellow backlight that you had hooked up that way before, that might explain why you were able to get away with using no dropping resistor.
 

KE4NYV

New member
OK, well I keep a stock of 2W 39 Ohm resistor for things like this, so I'll give that a try with the replacement I have comming.

Thanks,
 
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