NHD‐5.0‐800480TF‐34 Controller Board Back Light (B/L Enable)

[MidknighTrain]

The datasheet for this controller board can be found here:
http://www.newhavendisplay.com/specs/NHD-5.0-800480TF-34%20Controller%20Board.pdf

I'm having trouble getting the back light to turn on. After looking more carefully at the board, pin 3 (B/L Enable) on the 34-pin MPU side isn't connected to pin 2 on the 40-pin LCD side (there isn't any pathway leading out from pin 3). I'm pretty new to doing embedded programming and stuff, and I was wondering how I can turn on the back light for the display? Is it possible using this controller board? The display I'm using is the NHD-5.0-800480TF-ATXL#-CTP if that info is needed.

Also, according to this datasheet here for the LCD, http://www.newhavendisplay.com/specs/NHD-5.0-800480TF-ATXL-CTP.pdf, it says that the back light requires 60 mA @ 19.2 V, but on the other one for the controller board, it says 20 mA @ 23.1 V instead. Does this means that either or can be used, or....what? Sorry I'm a little confused at this part.

Thanks

[Saurabh_B]

Hello,

The backlight enable pin is an external signal that allows you to turn the backlight on or off.
It is normally tied high and will allow the backlight to remain running once VDD and VSS have been applied to the controller.

I did just confirm that this controller board will power the backlight, however it is normally black. Once power is applied to the backlight and the internal drivers of the display; the screen will flash for a fration of a second and go black.

[MidknighTrain]

Hi Saurabh_B,

I'm not quite following. Does this means that the B/L Enable pin should be connected to a GPIO pin on my microcontroller to be toggled HIGH or LOW to control the backlight? The datasheet says the B/L Enable pin should be connected to a power supply. But if I do connect it to an appropriate power supply, how would power go from that pin, which is pin 3 on J3 molex adapter, to pin 2 on J1 molex adapter? I do not see a pathway connecting the two pins. Or are they somehow connected and can't be seen externally?

[Saurabh_B]

The backlight enable pin is not directly connected to pin 2 of the TFT. The Controller itself has a built in voltage booster, which is tied to VDD.

The backlight enable pin can be tied to a GPIO or be left floating for the backlight to power on.

[MidknighTrain]

Hi Saurabh_B,

I've just tried to power on the LCD and the backlight, but nothing happened, not even the flickering that you were talking about. I connected VDD to 3.3V, GND to GND, B/L Enable signal to a GPIO pin, and also the DISP signal also to a GPIO pin. I tried driving both of these signals HIGH, and got nothing. Also tried just leaving each one (and both) floating as well, but nothing also.

Thanks

[Saurabh_B]

Did you try to power this display on with 19.2V at all?

[MidknighTrain]

Hi Saurabh_B,

No I did not. I only provided it with 3.3V. I wasn't sure if I should connect VDD to 19.2V since the datasheet says it can only handle ~3.3V. But if that's how the controller is setup to provide appropriate power to both backlight and VDD at the same time using 19.2V, then I will try to do as you said.

Thanks

[Saurabh_B]

Do not apply 19V to the board.

What is the current allowance for the VDD pin you are applying?

[MidknighTrain]

Hi Saurabh_B,

If I'm using the multimeter correctly (sorry I've never used one before), the launchpad I'm using is providing ~600mA @ 3.3V.

Thanks

[MidknighTrain]

Hi Saurabh_B,

I found out the mistake that I made, and I'm terribly sorry for wasting your time. I misread the direction of the pin on the FPC adapter breakout board, so I was connecting pin 33 (thinking that it was pin 2) to VDD instead of the actual pin 2.

Thanks

[Saurabh_B]

Thats good to hear, luckily the last 2 pins are no connects, so you shouldn't have anything short out on the board.

[MidknighTrain]

ISSUE RESOLVED. PLEASE IGNORE THIS MESSAGE.

Hello Saurabh_B,

Sorry for reopening this issue, but I just have one question. Is it possible to turn off the back light using this controller? I tried connecting the B/L Enable pin to a GPIO and toggling it on and off, but that didn't have any effect. I'm hoping not to leave the back light on the entire time, as currently it is always on as soon as I supply VDD.

Thomas