I am planing to create kind of a display with LEDs. Round or square, the board's expected size could be around 30 x 30 cm. LEDs' position is not expected to change; just the programing of the driver. Number of LEDs expected to be, most probably, around 64, laid in straight lines. Accuracy of the LEDs' location IS important.

At least for the first attempt (not sure if there would be a second) what is the best advisable technique? a cardboard piece, soldering wires to connect them to drivers and micro in charge, a PCB ( have to order it custom made and locally, it is expensive), or...?

Used to use veroboard in the last years, I realized that here it would be unusable because of the exact location of each LED they cannot provide. Discarded it already.

I am open to suggestions. The size of this and long runs of traces/wires, is of concern.

Help / suggestions, appreciated.

 

Make a PCB for the LEDs and use an overlay to align them during assembly.

Search for assembly of 8x8x8 LED cubes to get some ideas for aligning.

I want to make a scrolling LED sign and am still working on ideas for making sub arrays and joining them together.

 

Make a PCB for the LEDs and use an overlay to align them during assembly.

Not sure I understand that. Do you mean a full 30x30 PCB?

 

SMT can be laid down very accurately. For through hole LEDs you can make a fixture out of aluminum or Delrin that has at least a sub-array of holes sized to align the LEDs while soldering. Outfits like Bivar have all kinds of LED mounting stuff, too. Maybe you could use their light pipes in a precision-drilled array on a sub-panel. That way, LED alignment isn't as important.
Good luck.

 

If you use standard round 5 mm LED's you can mount them in tight fitting holes in a piece of plastic.
I use a 0.200" drill and it works perfect.

Vectorboard with 0.1" holes can be used, just stand the leads off a bit so the leads can bend to your exact positions, you will never be more than
0.1" off. Place the LED's in the holes, slide the board down over it, so it's all in perfect alignment.

Break them up into groups, so you can remove and fix them without tearing the whole thing apart.

Long runs are a non issue here- the LED's aren't going to care.

 

Do you mean a full 30x30 PCB?

Yes. You could cut down on cost by working out a method to make smaller boards, e.g. 15x15 cm, and connecting them edge to edge. You could use right angle male/female headers (my current thinking for my case), or card edge (but expensive connectors).

I did a 5x7 LED matrix to test my hardware and software for my scrolling LED display project. I used 3mm LEDs, because I have thousands on hand, mounted in female header strips that were, in turn, hand wired on perf board. I aligned the LEDs by hand, but would have created a jig if that turned out to be too difficult.

 

Yes. You could cut down on cost by working out a method to make smaller boards, e.g. 15x15 cm, and connecting them edge to edge. You could use right angle male/female headers (my current thinking for my case), or card edge (but expensive connectors).

I did a 5x7 LED matrix to test my hardware and software for my scrolling LED display project. I used 3mm LEDs, because I have thousands on hand, mounted in female header strips that were, in turn, hand wired on perf board. I aligned the LEDs by hand, but would have created a jig if that turned out to be too difficult.

Aha, bringing size down to reasonable cost per board with several boards. Worth to try on the drawing board. Paper, ruler, pencil...and eraser to see with what I come out.

 

SMT can be laid down very accurately. For through hole LEDs you can make a fixture out of aluminum or Delrin that has at least a sub-array of holes sized to align the LEDs while soldering. Outfits like Bivar have all kinds of LED mounting stuff, too. Maybe you could use their light pipes in a precision-drilled array on a sub-panel. That way, LED alignment isn't as important.
Good luck.

Have to explore those SMD. Never used one yet.

Have to explore the rest of your suggestions.

Gracias John.

 

A couple of suggestions:

If you can, drive each LED with its own latch and driver because multiplexing makes the image subject to artifacts, especially if the viewer is walking or riding.

If you have to multiplex use the highest refresh rate you can manage. Also, it is helpful to scan vertically using whole rows because saccadic movement (of the eye) which is responsible for many artifacts when the viewer is not moving is faster in the horizontal direction.

If you are using RGB drive all three color channels simultaneously. Driving separate fields can result in some very annoying color artifacts.

 

How many boards ?
I have used Sensacell's suggestion twice before with corrigated cardboard 3 ft. X 5 ft. 250 lights, & .02 in. tin plate backed with cork sheet, about 10 in. X 7 in., 98- 3 mm R, G LEDs.; electronics both on separate boards. No problem with accuracy. of layout or punching.
A sketch of LED layout would be helpful.

 

You need to describe what you are looking for in a bit more detail.
Do you mean something like this?
https://www.adafruit.com/product/2278

 

Regular grids are of NO use to me. In one line, LEDs are not equidistant.

Lines are not parallel to each other.

 

I am planing to create kind of a display with LEDs. Round or square, the board's expected size could be around 30 x 30 cm. LEDs' position is not expected to change; just the programing of the driver. Number of LEDs expected to be, most probably, around 64, laid in straight lines. Accuracy of the LEDs' location IS important.

At least for the first attempt (not sure if there would be a second) what is the best advisable technique? a cardboard piece, soldering wires to connect them to drivers and micro in charge, a PCB ( have to order it custom made and locally, it is expensive), or...?

Used to use veroboard in the last years, I realized that here it would be unusable because of the exact location of each LED they cannot provide. Discarded it already.

I am open to suggestions. The size of this and long runs of traces/wires, is of concern.

Help / suggestions, appreciated.

Hello Agustín. Have you looked at the way I print and etch PCB's? It might come in useful for your purposes.

 

Regular grids are of NO use to me. In one line, LEDs are not equidistant.

Lines are not parallel to each other.

I recently made a project for someone with 108 LEDs all well aligned on a 110 cm x 30 cm. All had to be positioned perfectly. I printed letter sized pages and taped them to a sheet of plywood, marked the position of each with a scribe, drilled an appropriately sized hole (5/32 allowed just the dome of the LED to fit snugly). Then I did point to point wiring on the back with all wires going back to a PCB.

Luckily, my LEDs were in groups of three to make segments, so I could solder those in series.
I ended up with "characters" of 9-segments.

It worked out very well. You are correct that even a small, 1mm, positioning error is easily noticed.

Note: the high brightness (GaN) red LEDs are are so bright they saturate the camera and look yellow/orange on video.

 

I recently made a project for someone with 108 LEDs all well aligned on a 110 cm x 30 cm. All had to be positioned perfectly. I printed letter sized pages and taped them to a sheet of plywood, marked the position of each with a scribe, drilled an appropriately sized hole (5/32 allowed just the dome of the LED to fit snugly). Then I did point to point wiring on the back with all wires going back to a PCB.

Luckily, my LEDs were in groups of three to make segments, so I could solder those in series.
I ended up with "characters" of 9-segments.

It worked out very well.

Note: the high brightness (GaN) red LEDs are are so bright they saturate the camera and look yellow/orange on video.

I'm getting a "This video is private" message when I try to play it on YouTube

 

I'm getting a "This video is private" message when I try to play it on YouTube

Try again

 

Try again

Nice! ... that looks like one of those old Star-Trek alien control panels with alien characters!

 

Nice! ... that looks like one of those old Star-Trek alien control panels with alien characters!

The person I made it for wanted it a wall-sized version of this...
(He is adding the doo-dads to make it look more "accurate"

 

The person I made it for wanted it a wall-sized version of this...
(He is adding the doo-dads to make it look more "accurate"

Now I get it! ... no wonder those characters looked strangely familiar! ... how did you implement the sequence? plain old gates, or did you use an MCU? ... what's he gonna do with it? display it in his man-cave? ... and what about the best part of that scene? The laugh, I mean... is your friend going to include it in whatever he's planning? ... sorry to bombard you with so many questions... but that thing is just soooooo cool!!!

 

Now I get it! ... no wonder those characters looked strangely familiar! ... how did you implement the sequence? plain old gates, or did you use an MCU? ... what's he gonna do with it? display it in his man-cave? ... and what about the best part of that scene? The laugh, I mean... is your friend going to include it in whatever he's planning? ... sorry to bombard you with so many questions... but that thing is just soooooo cool!!!

I put a description of how it works on the YouTube post - click the arrow in upper right of video and then click the link it gives you.

All of the sound effects and display control are a single PIC18F46K80 (it was the only PIC I had in my bin with dual channel PWM so I could (more easily) make much more complex (richer sounding) audio.

In the 80-step countdown mode, each digit is hard-coded into the firmware. Once the countdown completes, it reverts back to a "display mode" where characters are randomly generated and change slowly with no sound - kind of artistic effect for the museum.

Like in the movie, The user has to supply the laugh.