LED Spacing For Making Name

[bostonman]

I'm thinking of making a circuit that flashes individual LEDs in sequence to spell a name; we can call it ABCDE for purposes of discussion.

At the moment I'm exploring options to drive it (I know a 4017 is the choice, but not sure if I can get more resolution/channels using an FPGA).

Anyway, I'm curious how far apart to space the LEDs so it's not blurry, and brightness. I'm thinking tiny surface mount so they are somewhat invisible when off, and then clearly spells ABCDE when on. Also, how big should I make each letter to avoid using many LEDs (I'd be soldering by hand) to fill each letter, but not so small that the letters are not clear.

I've seen through-hole LED projects, but, when off, the LEDs make it appear too obvious with little surprise to the naked eye when lit.

[bidrohini]

As far as I know, there is no thumb rule for spacing. Many LED strips have 1/4" distance between the LEDs. Some have a bit more. I think it's better to make a small prototype first. The following links may help you.

https://www.theengineeringprojects.com/2022/03/introduction-to-led-pcb.html

https://www.sea.com.ua/en/led-lighting-solutions/
 

[Psi]

There's a chip that will do this all itself for a  5x24 display.
It even has internal boost circuit so you can drive it from 2.7-5V but still drive any voltage LED.

255 brightness steps per led
4 way scrolling
etc..

I've used it with tiny white LEDs and it was bright enough that you could put a diffuser over the top and make it invisible but still see text clearly

https://www.digikey.co.nz/en/products/detail/stmicroelectronics/STLED524/4928003

[Martian Tech]

It's not clear from your description exactly what you are trying to do, but it sounds expensive and time-consuming.  How about just using an available display like this:
https://www.ebay.com/itm/222425118866

[Watth]

What about programmable LEDs?

[bostonman]

It's not clear from your description exactly what you are trying to do, but it sounds expensive and time-consuming.

It's an idea I had to have the LEDs aligned in cursive lettering to spell a name. Each LED would start illuminating slowly and the speed would increase until the name is clearly visible (maybe making all the LEDs full on at the end).

At the same time, I'm thinking it's not worth it because the person receiving the gift wouldn't know whether I put the effort into aligning individual LEDs or just an LCD.

[james_s]

Nobody can tell you how big to make it, that's entirely your decision. You could use tiny 0402 LEDs or you could use 10mm LEDs or even power LEDs inside some kind diffuser and make the letters many feet tall. There is no rule on how close together to put the LEDs either, but the closer they are, the smoother any animation will be. If you put the LEDs behind a diffuser such as some kind of translucent tubing then that will blend the light and you can get away with wider spacing. It totally depends on the look you're going for, your budget and how much effort it's worth to you.

[bostonman]

Nobody can tell you how big to make it, that's entirely your decision.

You're absolutely correct. I believe initially I stated that I wanted small surface mount (but didn't indicate 0402).

Whether I do the project or not, I guess I began thinking about brightness and angle of light. If the LEDs produce very wide angles of light, then it would bleed over making it look less crisp.

Guess that was the basic question I was seeking, but, either way, you're correct, nobody can tell me what look to go with.

[themadhippy]

Hows about  addressable leds,not only would it make the fading easier,but you could have each letter in a different colour

[bostonman]

That's interesting, I'll have to research them.

[Le_Bassiste]

Anyway, I'm curious how far apart to space the LEDs so it's not blurry, and brightness. I'm thinking tiny surface mount so they are somewhat invisible when off, and then clearly spells ABCDE when on. Also, how big should I make each letter to avoid using many LEDs (I'd be soldering by hand) to fill each letter, but not so small that the letters are not clear.

as a rule of thumb, angular resolution of the human eye is approx. 0.5 .. 1 arc-minute.  you can use that to determine required LED-distance vs. viewing distance.
(1 arc-minute = 0,017°)

[Infraviolet]

My guess is the main trick would be to use some sort of difusser material, some sort of translucent plate infront of the layer where the LEDs are mounted, this will make the exact LED pattern invisible when they are off, but each will glow with a softened wide-area glow when turned on.

If you're making it as small as possible my guess would be that the text height might take 5 LEDs, and the width of each character might be 3 LEDs, they wouldn't be a nice font but I think they would be recognisable as letters, think of old figure eight type displays for 0-9 digits, but then a few more to make the full alphabet of letters feasible. This will be a lot easier with a diffuser to turn point-source LEDs in to area glows.

[ledtester]

...
Anyway, I'm curious how far apart to space the LEDs so it's not blurry, and brightness. I'm thinking tiny surface mount so they are somewhat invisible when off, and then clearly spells ABCDE when on. Also, how big should I make each letter to avoid using many LEDs (I'd be soldering by hand) to fill each letter, but not so small that the letters are not clear.

I've seen through-hole LED projects, but, when off, the LEDs make it appear too obvious with little surprise to the naked eye when lit.

You might get some ideas from looking at the design of "LED name tags", e.g.:

https://www.aliexpress.us/item/3256804533014689.html

They use a dense matrix of SMD LEDs.

[mariush]

There's drivers that can control big matrixes of leds like for example Lumissil IS31FL3729  : https://eu.mouser.com/new/lumissil/lumissil-is31fl3729-matrix-led-drivers/
It can do 16 x 8  or 15x9 arrangements (or in theory whatever vertical height you want, it's up to 16 channels) and you can have 256 levels of brightness , and lots of features as you can read above.

Or for example this big boy with up to 39 x 9 matrix, IS31FL3741A : https://eu.mouser.com/ProductDetail/Lumissil/IS31FL3741A-QFLS4-TR
This one can also be configured to work in RGB mode, 13 rgb x 9... see datasheet : https://eu.mouser.com/datasheet/2/198/IS31FL3741A_DS-1839558.pdf

Then it's just a matter of using a small microcontroller to determine what digits or what lines must be visible and split that info across multiple such drivers, if you need to use more than one.
 
You don't have to arrange the actual leds in a dot matrix arrangement, you could use one of this drivers to drive the leds that are spread on curvy letters, you just have to be aware in your program where in the dot matrix each led maps to.

but for fast development and if pcb space is not an issue, you could just have those  shift register style linear led drivers that are available in DIP packages so they're easy to prototype... they're like shift registers but let you set the max current through leds using a single resistor) and some have ways of giving them extra commands by shifting bits into them while a pin is set high or something like that.
So every time you'd want to update the leds, you'd just shift  8 x number of chips you end up using and all leds get updated at same time.

[Zero999]

I''m not sure exactly what you're trying to do.

The minimum number of LEDs to give the full ASCII character set (this consists of common symbols and all the numbers, Latin capital and lower case letters) properly is 5x7 = 35. There are modules available from Digikey, Mouser, Farnell, RS etc.

https://uk.farnell.com/multicomp/703-0193/display-dot-green-1-2-5x7-cc/dp/2112219