LED Video Panel from Maker Faire questions

Paul, I have some questions about the LED video panel project.

I'm curious if you used any inline fuses?

The junction box that the power supplies are connected to, what is going on in there?

What is the clear box for?

For the power that you are running to the strips are you using several spades under one post?

Is there anything you would do differently the next time around?

Thank you,
-Ron

For anyone else coming to this thread, it's about this LED video panel we built for Freescale in May 2014.

http://community.arm.com/groups/embedded/blog/2014/05/23/led-video-panel-at-maker-faire-2014

takedown said:

I'm curious if you used any inline fuses?

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No, but now that you mention it, that does sound like such a good idea. Those six power supplies are rated for a combined total of 240 amps of current.

The junction box that the power supplies are connected to, what is going on in there?

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120 AC comes in, hot goes through a switch, and then feeds out to the 2 sides, powering up 3 power supplies on each side. It's really very simple.

What is the clear box for?

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Spare parts.

Really, we made this thing for Freescale to take to Maker Faire and other shows. The box has a spare for every part, plus some tools and other supplies they might need. Apparently something did go wrong at some point when they took it to another show, maybe in Detroit, but they were able to get it back up and running by swapping out a part.

For the power that you are running to the strips are you using several spades under one post?

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The wires are merely tinned and wedged under the screw terminals. Yes, several go to each post.

Is there anything you would do differently the next time around?

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It actually went really well. Aside from charging 5X as much (we only billed them for materials, since they've been pretty helpful us on several occasions) and not trying to cram the entire build into only 3 weeks, I'd probably do it about the same.

Paul,
I've got a hopefully simple question. Do you have a sketch on how its wired up?

Specifically I'm wondering on power, I read that making long runs isn't the way to do it.
Also how you've got one micro controller done.
Sorry if I've missed a link somewhere.

I ask as I'm looking to create a small forest of hanging wires, each about 1.5M long, to make a 3D lighting space you can walk through.
So my task is how to get the power and control signal to each drop and if I space them apart too much how much of an issue this might create.

I'm struggling with the electrical side of this very cool project you posted.

If you haven't done so, you might want to look at the Octows2811 (http://www.pjrc.com/store/octo28_adaptor.html), which uses cat6 cables for the data transmission, and you use separate power/ground wires to power each strip. I would suspect one issue might be the time it takes to send the data through the separate strips (ws2812b's have fairly strict timing controls). I've heard of some people using RS-485 between the microprocessor and the LED strip.

AussieFred said:

Paul,
I've got a hopefully simple question. Do you have a sketch on how its wired up?

Specifically I'm wondering on power, I read that making long runs isn't the way to do it.

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You can see the wiring on the back side at 0:28 in the video. Both sides look pretty much the same, with 48 pairs of #20 wire (one pair per strip) from those the 3 power supplies on each side.

That LED board was build almost 1 year ago. I took those photos & video and wrote that blog at the time. Display was delivered to Freescale at Maker Faire. I no longer have it. I'm not planning to produce any more documentation regarding that particular project.

Adding Stereo Out???

Hi Paul!

First, thank you so much for this sharing this project! It has been extremely valuable for adapting your code to one I am currently working on. One question has now come up that I can't figure out:

I am basically trying to do a similar project with synced audio and LED playback, but it needs to have good quality STEREO audio output..

As far as I can tell the PJRC audio board does not work along with the OctoWS2811 library, so I decided to try the optical Spdif method.

I have gotten as far as to get everything mostly working that way, but when the spdif out is called up in the sketch, the LEDs begin to glitch while playing the content. I am guessing this is the Spdif timing interrupting the Octo timing? Also I cannot figure out configuring the add audio portion to add a stereo file..

I am hoping you may have some ideas/suggestions or another way to get a way to get a good stereo output while streaming to LEDs.. I am very close to being able to realize my project otherwise. I will be using only a relatively small amount of pixels (around 400). Just need to get them synced up with good stereo sound!!

Thanks so much for any help!!

Sachismo said:

I have gotten as far as to get everything mostly working that way, but when the spdif out is called up in the sketch, the LEDs begin to glitch while playing the content. I am guessing this is the Spdif timing interrupting the Octo timing?

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My guess is perhaps this is a DMA priority problem? The WS2812s require tight timing, so maybe the audio DMA is running at a higher priority, causing the OctoWS2811 DMA to wait too long?

The DMA hardware does support 2 level DMA preemption, where a higher priority DMA interrupts a lower priority one. None of the existing code ever uses this feature, and until now it's never seemed like it'd ever be needed.

Also I cannot figure out configuring the add audio portion to add a stereo file..

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The code is all designed to adding a mono sound track. Of course it could be modified to add twice as much data, and code on the Teensy side will need to pull twice as much and feed it into the play queue objects.

Thanks Paul!! At least it still seems like it's possible!

Would the DMA interrupt settings need to be done at a library level, or could this be done within the sketch code?? Any further pointers on how to move forward with that would be greatly appreciated..

As for the stereo issue, I think I am understanding a little better now. I would probably need to embed 2 separate mono RAW streams and then read them out into 2 separate queue objects correct??