Choosing a screen for hand-held device - Page 1
Forum section: electronics / projects

author: JohnSL
author_rank: Regular Contributor
timestamp: April 10, 2017, 12:44:54 am
content: Hi,I'm in the process of choosing a display for a hand-held device that will be battery operated. I've been looking at LCD, TFT, and OLED displays, but I've been having a hard to understanding power characteristics of these different displays.For my device, I'm planning on using a rechargable LiFePO4 battery, and the other power hungry element will be an ESP8266. I've been looking at 700 mA/hr batteries, and I'm hoping to get an "operating" time of about 7 hours. This time will include a certain percentage of idle time for the WiFi, and also for the screen. So I think this is certainly possible (but will require real-world testing, of course).I'm guessing that I'll want to turn off the backlight or the screen to help conserve power, so one of the features I'm also looking for is whether the screen is readable without backlight or not. Also, I'm going to have a very lower power sleep mode, so I want to make sure I can disable the screen in this mode. Ideally, the current drawn in sleep will be micro amps.Finally, for size I'm looking for something around 1.5 to 2 inches. And it's OK if it's character instead of graphic. I should also point out that this is not a high volume or high price product (perhaps 10K units per year if I'm lucky).I realize this question is a little open ended at the moment. What technology would you use? Or are there other options you would suggest I look into?Thanks,-- John

author: DaJMasta
author_rank: Super Contributor
timestamp: April 10, 2017, 01:32:56 am
content: A character display is ok? Sounds like color isn't a priority... if you want low power consumption and readability in sunlight, how about a traditional LCD screen? If you're making enough of your product it shouldn't be any trouble getting custom symbols or whatnot as elements (like handheld multimeters do). If you don't mind the added expense and reduced update speed, eink displays could be a viable alternative - much lower power consumption (it will maintain the display without power) and higher contrast than your typical LCD modules.

author: JohnSL
author_rank: Regular Contributor
timestamp: April 10, 2017, 02:05:45 am
content: Thanks blueskull and DaJMasta. The device will be used inside, so only overhead lights for use when the display is not backlit.And yes, a character display is fine. I'd prefer a graphical display to give me more control over what's shown, but a character display would work as well. The size is limited by the width of the device to about 2 inches. Height is less of an issue, which is why I did't provide an aspect ratio.So a couple of questions. What are the costs like to get a custom display? There are some parts of the display that will have dedicated functions (elements on/off or numbers). But I also need generic text for part of the display, to handle a menu system.eInk would be fine for this application, as I don't need fast updates. However, there seem to be very few out there, and I'd be concerned about the long-term availability of them. Perhaps I've simply not looked in the correct places for these displays.

author: ebclr
author_rank: Super Contributor
timestamp: April 10, 2017, 02:28:02 am
content: If price is not an issue e-paper work with extremely low powerhttp://www.ebay.com/itm/E-ink-E-paper-display-IPS-2-04-inch-GDE021A1-172x72-/151818409532?hash=item235915163c:g:UB8AAOSwQPlV-NWN