What display type to use (LCD, TFT, OLED, eInk, ...)

(continue discussion from Adafruit_mfGFX custom font need help)

@peekay123 and @ScruffR first of all thanks for all the help. I have tried as you suggested but the result is not what I was expecting for the lcd. Maybe I choose the wrong LCD for this project. @peekay123, since you play with this lcd before please correct me if I am wrong with this lcd. What I found out was, to see anything from the LCD, the so call back light LED pin must be power on all the time. This is good until its night time it glows in the dark like a flashlight. By controlling the brightness of the LED, it dims but still glows in the dark or either I can’t see anythings on the screen. I guess what I want was a regular screen that does not shine in the dark with a back light that turns on when the user want to do something. Is this not the lcd for the jobs?

As an alternative, will digole http://www.digole.com/index.php?productID=1222 do what I want or other suggestion that will not break the pockets, min 2.4" display?

All TFTs will have that “issue”, since this is the way they produce the picture - by filtering white light which shines through the actual display from behind, but don’t reflect (hardly) any ambient light - hence you can’t see anything with backlight off.
OLEDs would be actively producing light in each pixel and hence don’t need backlighting.
ePaper/eInk displays mainly rely on reflecting ambient light where some of them also feature back lighting.
And then there are so-called transflective displays which mainly work like TFTs but also allow for some ambient light to enter the display and reflect the image, but these are not common as shields.

But you can control the backlight just like that. Add a photo sensor that dims the backlight when it gets darker, have some idle timer that switches the backlight off when not in use and back on when the user interacts.
And if you choose to have a mainly black image most of the backlight will be filtered out anyway (depending on the quality of the display)

@ScruffR, photo sensor is a great idea. Thanks :smile:

What about liquid crystal display such as http://www.ebay.com/itm/2-4-Inch-TFT-Liquid-Crystal-Display-LCD-Module-Touch-Screen-For-Raspberry-Pi-GL-/122077754491?hash=item1c6c66b47b:g:z7AAAOSwHoFXqZA~? Will this have the same issue?

As said: All TFTs work that way.
But I wouldn’t call it an issue, it’s just how these things work and you need to find a way to deal with it or dismiss TFTs for your use and go for OLED or eInk.

I have one of the Honeywell Thermostat in my house. Do you know what type of screen does they used? Its monochrome but it does what I want. Sorry my knowledge of Display is limited trying to learn as I go. Thanks

I guess these are mere LCDs

A picture would help.

Yup, that’s a mere LCD. These use the reflected light mainly and only need a very dim backlight for night visibility.

@sheng, @ScruffR, the digole provides software control of the backlight so you can turn it on or off though you can’t control brightness.

You can also add a Digole universal controller to an LCD to a lower resolution LCD that can work in daylight and can be backlit at night. You get the benefits of the Digole controller but with a display that might suite your needs more.

@peekay123, will it still glow in the dark when its on without the backlight or its total dark with the backlight is off? I don’t have one on hand to play with at this point.

@sheng, TFT display require backlighting to work. The other (lower res) LCD that I linked to can work in daylight without the backlight.

@ScruffR, when you said its mere LCD, what does it mean? Can this work with P1 module?

@sheng, first, I noticed that you are getting off topic of your original post. Second, you need to learn about reflective versus transmissive LCDs. Please do a Google search or look in Wikipedia to educate yourself. Then, please start another topic regarding choosing a suitable display. Or perhaps @ScruffR can do that and move your questions over to the new topic.

1 Like

That’s a different display technology which works different to the ones mentioned above. If you want to know how they exactly work I could elaborate more, but you can probably find tons of resources yourself.
And yes, LCDs do work with P1s as well, since it doesn’t matter what display technology you use, you only need a controller the P1 can talk to :wink:

@peekay123, I guess the display @sheng has shown a picture above does allow for PWM backlight dimming (down to zero, I’d assume), too.

Consequently I’d just try to go with that display and see what’s possible with it (change of color scheme, dimming, off/on control, …)

@ScruffR, you are correct. It seems with the latest firmware the Digole TFT displays allow the user to control brightness. The nice thing about Digoles is that you can interface via UART (serial), I2C or SPI.

Done! Thanks for the heads up on the “off topic” :+1:

1 Like