LCD Backlight Brightness

Question

I've gotten to the point in my build where I am working with some LCDs. I have them working and display information and I am now working on the backlight brightness. I connected the backlight +5v to the brightness control 0 as a PWM device and I got the results I was hoping for. I can control the backlight brightness with the rotary encoder I have setup.

My question, what would the power draw be like with this setup if I had multiple LCDs. I am using multiplexers and DM13A chips connected to an external power supply so the draw from other items in the cockpit shouldn't be to high. Would an external PWM driver be a better option for this?

Is there a way to connect all this up to BUS #1 and BUS #2 on the arduino to turn the LCD backlight on and off as well?

Great software and great work! Many thanks.

Answer 1

Conrad,

If you use the external (slave) SimVimLCD driver, you can use the  pins A5,A6,A7on the slave board as PWM control for the backlight (you can see that when selecting the LCD slave table in the configurator).

These outputs are PWM signal that depend on the Bus1,2,3 voltage and when a bus you need is off the screens are off too.
Also, the first output is controlled by  the Avionics Master. I'm going to remove the bus 3 and add something else.

Yes, it better to use additional driver for several displays.

Regarding the current consumption - you need to estimate it yourself, each display type  can have different backlight current and the LEDs connected to the  LED drivers may consume a lot of power when all them are in ON state.

https://realsimcontrol.com/simcom/index.php/4998/external-power
Vlad

Comments

Hi Vlad,

Thanks for the answer! I am currently using an external power supply, thanks!

If you're going to remove bus 3, may I suggest you consider replacing it with brightness control that can be connected to a brightness knob?

Again thanks for your hard work!

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Now, (in new upcoming soon update) I have added more reliable power control for the LCD board.
The pin #19 / A5  is used as  voltage output for electric bus 1.  When the bus voltage drops, the LCD backlight brightness decreases (until completely dimmed).

Also, now you can link any previously assigned BRT knob to the LCD board. And the backlight will be adjusted by the knob along with the bus voltage. The pin output A5 is a PWM signal for the backlight (+input) - can be used directly for 2-3 LCD or  through the FET booster..

See the configurator (click the LCD board.)
The new version is going to be released (soon).

Vlad

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Great work as always! I look forward to the next version.