Help finding really big 7-segment LCDs - Page 1
Forum section: electronics / beginners

author: AndrewM
author_rank: Contributor
timestamp: September 30, 2020, 01:14:52 am
content: Where would I find really big 7-segment LCD displays in low quantities? I'm thinking 5-8cm height numbers, but I'm not too picky as long as it's really big. I need 4 digits per display, but I can make do with using multiple parts to make that up, and extra digits aren't really a problem if I have to go to 6 or 8 or whatever.I've tried searching all the usual suppliers, but they seem to top out at about ~2cm character size. Same goes for digging through aliexpress and amazon and ebay.I don't really think most LCD manufacturers would be interested, given that I only need a few of these things for a prototype run of ~5 units.Is it worth trying to hack a big LCD clock? (eg:https://www.amazon.ca/LAWOHO-Temperature-Multi-function-Backlight-Automatic/dp/B0774CTG1Q/)

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 30, 2020, 01:51:40 am
content: 5cm is not "very big".This is getting big:https://hackaday.com/2020/07/12/7-segment-display-is-no-small-feat/On hackaday you can also find other home-built big displays. Just search that site a bit.Velleman is a company that sells some parts and kits. Among their assortment is:https://www.velleman.eu/products/view/?id=353344I have not looked at prices though.7-segment displays are easily commercially available upto around 10cm, although the bigger displays are less common. I've seen them on Aliexpress for example.Here an example from ebay:https://www.ebay.de/itm/Big-10cm-4-inch-RED-7-segment-LED-display-common-Cathode-EU-seller/324311214994Futurlec has some displays, but the price looks a bit ridiculous to me:https://futurlec.com/Single_7_Segment.shtmlThese are 70mm:https://www.jaycar.com.au/super-large-seven-segment-display/p/ZD1850Also:The bigger displays often have multiple LED's in series, so if you go to for example digikey, and then sort on "forward voltage", you see some 13 cm high display's:https://www.digikey.com/products/en/optoelectronics/display-modules-led-character-and-numeric/92?FV=-8%7C92&quantity=0&ColumnSort=-319&page=1&k=7+segment&pageSize=25&pkeyword=7+segmentAnd you'll find that other bigger resellers will have similar displays. If you could not find them, its more because of your search skills then of their eagerness to sell stuff.About one out of 4 links here seems to be over 5cm:https://html.duckduckgo.com/html?q=7+segment+big

author: ledtester
author_rank: Super Contributor
timestamp: September 30, 2020, 02:13:29 am
content: The OP is looking for LCDs.

author: AndrewM
author_rank: Contributor
timestamp: September 30, 2020, 06:43:31 am
content: Thanks for the suggestions, but I've looked at that stuff and none of it will work for me.I specifically need LCD. It's for use outdoors and needs to be visible in direct sun, and I have a fairly tight power budget for this

author: james_s
author_rank: Super Contributor
timestamp: September 30, 2020, 07:16:58 am
content: Would this work for you?http://www.e-paper-display.com/products_detail/productId=141.html

author: greenpossum
author_rank: Frequent Contributor
timestamp: September 30, 2020, 07:27:34 am
content: Would flip displays work? Not cheap though.

author: AndrewM
author_rank: Contributor
timestamp: September 30, 2020, 02:42:51 pm
content: Quote from: james_s on September 30, 2020, 07:16:58 amMaybe. The problem with e-paper is the low-temperature performance.. This needs to work outdoors in all weather in Canada. Ideally it works at temps down to -30C. That product might work, most e-paper I was looking at earlier had an operating temperature limit of 0C or so. I'll send that place an email, maybe they'll sell me 25 of those or so.Quote from: greenpossum on September 30, 2020, 07:27:34 amMaybe. Would be even more expensive once I take into account durability requirements. This thing might get kicked around a little and I'd like it to keep working.

author: Cerebus
author_rank: Super Contributor
timestamp: September 30, 2020, 03:02:33 pm
content: Finding LCDs that will work across the whole 'outdoor Canada, eh' temperature range is going to be a problem I would think, let alone just finding big ones. Either you are going to need heating for low temperatures (there goes your power budget) or you're going to have to re-think your choice of display technology.

author: Benta
author_rank: Super Contributor
timestamp: September 30, 2020, 05:45:37 pm
content: LCDs at -30 C? Good luck!

author: james_s
author_rank: Super Contributor
timestamp: September 30, 2020, 06:41:58 pm
content: Quote from: AndrewM on September 30, 2020, 02:42:51 pmThe link I posted is not e-paper, it is LCD. Ignore the fact that the website is e-paper, you can buy the same LCD modules elsewhere, just look based on the part number. For what it's worth, LCD tends to not perform well at low temperatures either however they are cheap enough that you could buy a few to evaluate.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: September 30, 2020, 06:52:04 pm
content: Oops.All those 3 letter abbreviations make me dizzy.Sorry for the noise.

author: ogden
author_rank: Super Contributor
timestamp: September 30, 2020, 07:06:28 pm
content: You may consider electromechanical 7-digit display

author: floobydust
author_rank: Super Contributor
timestamp: September 30, 2020, 07:27:41 pm
content: It's ok I went after LED displays too lol. Big LCD digits are extremely rare. I've seen them once in a Russian digital clock for sale on eBay and 4"https://www.opticsplanet.com/sports-radar-remote-large-lcd-display.html.OP, outdoors low temperature (-30C) LCD fluid requires higher drive voltage, so a +/-5V supply used. If you want reflective LCD outdoors, they are useless at night or in the shade. Straight sun cooks them and they get too hot and go black. The large segments have pretty high capacitance so drive current is also higher.It all depends on your power budget. You won't do this with a 3V coin cell for example.Green LED displays are very efficient nowadays and a proper filter and polarizer can work in straight sun. Flip-dot displays take a huge amount of current, many amps to flip.

author: Jwillis
author_rank: Super Contributor
timestamp: September 30, 2020, 09:08:29 pm
content: LUMEXhttps://www.mouser.com/datasheet/2/244/LCD-S101D22TR-1134315.pdfI think is 36 X 56 mm orhttps://www.mouser.com/datasheet/2/244/LCD-S101D14TR-1132149.pdfIs 19 X 34 mm slantedhttps://www.mouser.com/datasheet/2/244/LCD-S101D40SR-1776302.pdf101 mm height

author: JustMeHere
author_rank: Frequent Contributor
timestamp: September 30, 2020, 10:31:42 pm
content: This one is 5 cmhttps://m.aliexpress.com/item/32770071469.html?_randl_currency=USD&_randl_shipto=US&src=google&albch=shopping&acnt=494-037-6276&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shopping&aff_platform=google&aff_short_key=UneMJZVf&gclsrc=aw.ds&&albagn=888888&albcp=9594035441&albag=102695258807&trgt=296904913880&crea=en32770071469&netw=u&device=m&albpg=296904913880&albpd=en32770071469&gclid=CjwKCAjw2dD7BRASEiwAWCtCb3QHyiSAF-5PaW0aJsE4QJku6Z0JQDavvpoxf73LiPcvrUXjL6B0NBoCCpMQAvD_BwE

author: AndrewM
author_rank: Contributor
timestamp: October 01, 2020, 05:11:45 pm
content: Quote from: floobydust on September 30, 2020, 07:27:41 pmAnyone have an estimate on what my ballpark power draw would be for a ~10cm tall green LED 7-segment display with 5 digits?I could go that route I guess, and just make the thing a little thicker to stick more batteries in it.

author: james_s
author_rank: Super Contributor
timestamp: October 01, 2020, 05:18:05 pm
content: It depends on how hard you drive the displays. Some types of modern green LEDs are very efficient, they can be readable at 1mA or less per segment under normal room lighting. In direct sunlight you will probably need to push them pretty close to the 20mA max per segment.

author: floobydust
author_rank: Super Contributor
timestamp: October 02, 2020, 03:46:58 am
content: 4" LED 7-segment displaysare a common size datasheetLD40011AUWshows InGaN pure green is the most efficient followed by white. Each segment is 5 LED's in series so full 20mA at 15-17V, per segment (~10V for red) which is high voltage and you would need a boost converter depending on your battery pack.Not all segments are always lit, but an '8' is 140mA at 16V. If you multiplex an LED display, only one digit is ever on at a time. You're just scanning the 5 digits and letting the human eye fill the gaps.I would estimate 2.5W for full display power which can light up a room. You can save power by dimming the display if it's less than full sun with a good filter. Even 1/10 power or 0.25W is decent. You see these displays on Lotto signs at gas stations and easily visible 75 ft away.

author: Cerebus
author_rank: Super Contributor
timestamp: October 02, 2020, 01:53:17 pm
content: It's worth noting that human visual sensitivity is highest in the green (peaks at 555 nm) than anywhere else. So as well as green LEDs giving you the biggest bang for your buck in terms of converting electricity in optical power, they also give you higherperceivedintensity than other colours - a double win.

author: james_s
author_rank: Super Contributor
timestamp: October 02, 2020, 09:19:51 pm
content: What I would probably do is buy one or two each of several different types of display you are considering and then run some tests under conditions as close to actual operating conditions as you can find. You can hardwire them for static display or use an arduino or something for quick prototyping. That will allow you to take real world measurements and experiment with drive current and other factors.