12.1" Screen Power Issue?


#1

So I managed to miss the disclaimer that said the 12.1" screen would need a 12V 1A power supply. Luckily, I keep all of my extra wall-warts stowed away, just in case something like this happens. The closest three I have found are a 12V 500mA, a 12V 900mA, and a 16V 4A one (not close but the only one more capable)…

I decided to try the first two to no avail. I figured the 12V 900mA one would definitely be close enough to power the screen, but apparently not… Now, I wasn’t just going to plug in the crazy 16V 4A one, but I’m starting to think that something else may be wrong. I don’t know how the screen is supposed to “turn on” as I’ve tried all of the buttons on the breakout board for the controls and I don’t see ANY LEDs light up when I plug in the barrel of the first two power supplies.

Obviously, I’m going to run out and grab a 12V 1A power supply tomorrow and will try that, but as mentioned, I think something else might be going on considering how forgiving the RPi is with amperage and how I was only 100mA under for the screen.

I also didn’t add “hdmi_force_hotplug=1” to my RPi 2 config.txt file because the 12.1" screen is powered externally, not by the Pi, which was the reason given for the instructions for the 8" screen.

Can anyone describe the behavior of a working 12.1" screen? How do you turn it on? Does it need to have a signal to even light up and possibly light the LED in the control board? Anything would help, thank you!


#2

I have the 12.1 screen too. I bought the power adapter from pimoroni. Works perfect. The sceen comes on as soon as you flick the switch on the wall socket. You can turn it off on the bottom button of the pcb as per the pic. I would get the power supply from pimoron if i was you.


#3

Thank you so much for your help! I got it figured out. I went out and bought a new power supply that’s 12V and 1A. It works! The screen seems a bit dim overall. Even with the brightness turned up.

Do you think a higher amperage would make the screen brighter? I’m only talking about 1.3A or 1.5A.

Also, I haven’t found anyone else posting information about the OSD menu settings. There are some that I’m curious about but I have no idea what they mean and without documentation for the display board etc., it’s anyone’s guess. I’m talking about the settings like the “Mode” under the “Function” menu, set by default as “SYS3”. Any insight?


#4

Glad you got it working. At least you know it wasnt a faulty screen :)

I have my screen set at contrast 80 and brightness 80 (everything else default) I wouldn’t say it was dim looking.

Can you post a pic of the screen with some examples in games etc to compare?

One thing to note is that I put these settings in the /boot/config.txt file beforehand. (on the advice of someone else that has this screen)

  1. Uncomment hdmi_force_hotplug=1 (This forces HDMI Display for use)
  2. ADD disable_audio_dither=1 (removes static at high volumes)
  3. Uncomment config_hdmi_boost=4 (Provides more power to display)
  4. ADD max_usb_current=1 (disables power restrictions on USB so the display can work)

The screen is actually a samsung panel:

Panel Brand :
SAMSUNG

Panel Model :
LTN121XL01-N03

Panel Type :

               a-Si TFT-LCD                   , Panel 

Panel Size :
12.1 inch

                  Resolution : 
                  1024(RGB)×768 , XGA 

Display Mode :
PLS, Normally Black, Transmissive

         Active Area : 
                 245.76×184.32 mm
      
                      
         Outline : 
                 257.3×199.1 mm

Surface :
Antiglare (Haze 25%), Hard coating (3H)

Brightness :
300 cd/m² (Typ.)

Contrast Ratio :
700:1 (Typ.)

Display Colors :
262K
(6-bit)

Response Time :
30 (Typ.)(Tr+Td)

Viewing Angle :
80/80/80/80 (Typ.)(CR≥10) (L/R/U/D)

Frequency :
60Hz

Lamp Type :
9S4P WLED

Signal Interface :
LVDS (1 ch, 6-bit)

Input Voltage :
3.3V (Typ.)


#5

You mention setting your brightness at 80 etc. How do you manually set it? My screen appears rather dim too.


#6

Using the video board buttons. I cant remember the exact button combo. It wasnt difficult.


#7

Well thanks for the tip drokkeh, worked like a charm.