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Cfah0802a-ymc-jp

toofastdave1

New member
Hello,

I purchased 2 of the CFAH0802A-YMC-JP LCD's and have them hooked to a PIC microcontroller for operation. My problem is I can't get the contrast of the LCD to go above barely being able to read it. The yellow is so dimly lit, you can barely see it. I followed the schematics as stated in the manual, but no luck. The only way you can read it is if you turn the backlight on and then it's really bright! Problem there is it eats the battery quick...
Anyone have any suggestions? I have 2 that do the exact same thing. They look nothing like the picture on the webpage when lit with no backlight....

I see the jumpers (RA & RK) on the back of the PCB are not covered in the manual, what are they for? Can you solder resistors in line to keep the backlight on or should you use the adjstable method??

JUST FOR INFO: If a moderator is reading this, the links for registering are backwards. The over 13 age limit links to the under 13 webpage.

Thanks!
Dave
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Last edited:

CF Tech

Administrator
You must have a current limiting resistor in series with the backlight LEDs:

https://forum.crystalfontz.com/showthread.php?
threadid=62

For the contrast, please use about 1 volt at pin 3 (Vo) for starters. Usually, you put the ends of a 10K pot to Vcc (+5v) and Ground (0v), with the middle pin (the wiper) connected to pin 3 (Vo).

For small production (orders of more than 100 units) we can load a backlight current limiting resistor on the LCD (4-6 week lead time applies). For smaller prototype runs, please use an external Rlimit and optionally a pot to change the brightness.
 

toofastdave1

New member
I am using an adjustable resistor between VCC and VSS. The display just doesn't seem to want to go above barely visible. The only time you can really see it is when you turn the backlight on. Is this normal?

Dave
 

CF Tech

Administrator
Negative mode displays are very difficult to read without the backlight on. That is why there are no "backlight off" photos for them. :)
 

toofastdave1

New member
Ohhh Ok

That says it all... I guess the backlight will have to be constant on or pulsed to make the letters brighter... or just use a different LCD... I thought they looked cool, that's why I got em... but if they burn up too much juice, they won't work...

Any reason the jumpers on the back weren't covered in the manual...?? I see RA and RK are the inline resistor place holders, what about JF??

Thank you!
Dave
 

CF Tech

Administrator
By default, the display basically emulates the "industry standard", which is no backlight current limiting resistors installed.

For special order (100+ units, 4-6 weeks) we can factory load the resistors to your specification (ie: please install resistors to drive backlight from pins 1 & 2 at 50mA) which can save you components and connections in your production runs.
 
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