Electronics > Projects, Designs, and Technical Stuff

Need help making LCD display backlight dimmer

(1/5) > >>

Hello all,

I am using one of these displays and the dimmest setting is still too bright. 


Unfortunately the unit I have, what I believe is the backlight driver is unmarked.  The other chips are video processor (center) and dc-dc converter (left).  I believe the backlight driver is on the upper right. 

I have attached a higher resolution image of the board.  EDIT: Good grief there is a improperly soldered resistor in there. The one pictured is not in use it is a spare but ill have to attend to that resistor. 

Is there any way to dim this with hardware?  I did look up some backlight driver datasheets and I think some of them set brightness with a voltage reference range.   I was hoping it would be as simple as a resistor change but I don't think ill be that lucky.  I guess a filter in front of the panel is a last resort.

Not regarding your question, but is the capacitor right next to the quartz misplaced on purpose, or is this a case of tombstone effect?

What do you expect providing a blurry image? Most of the parts are unreadable.

The adafruit page you linked to has a link to the datasheet for the TFT, which shows that the controller has a built-in boost controller for the backlight.  The shitty application schematic shows that it only needs an external transistor, diode, inductor, and current sense resistor.  Should be pretty straightforward to trace that out and swap the current sense resistor for a higher value, which will give a lower current. 

The unmarked IC looks to be connected to the serial interface on the panel, so I would guess based on the datasheet and adafruit description that it's a little MCU to handle the one-button setting of backlight value via serial commands to the internal boost controller.

the dtasheet show you the needed voltage for driving the led backlight ...  you can build an current limitted driver,  like lm317 circuits  etc ...

Or you have to reverse engenier the pcb circuit to see  wich kind of control they have used, in the datashhet you see at least 2 ways of doing so,  probe the vled pins to see if its a pwm or dc control voltage ??

Adafruit could send you the schematics if you ask them ??


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version