My 32x RGB LED board

[allanw]

My 32x RGB LED board that I've been working on for a while. I made the LED holes too small so I had to surface-mount solder each one individually, which took forever.

It uses one TLC5947 per 24 channels, which does 12-bit PWM on each individual channel. All the MCU has to do is shift in 12 bits per channel, and send a latch signal. The PWM clock signal is generated by the TLC5947's, which makes it a lot easier to use than the TLC5940's. They can also be chained together. Here's a video of it in action:



If anyone wants some I might make a big PCB order and sell the boards for $5 each or something.

At full brightness it'll draw about 2A of current. The TLC5947's get pretty toasty when running them at 5V, but they work just fine at 4V and dissipate much less power.

Any ideas for improvements? I was thinking about adding space for an I2C accelerometer and gyro so that it could be waved around and have it do things based on orientation/acceleration.

edit: Here's a link to my blog post about it: http://electronoblog.allanw.org/2010/10/tlc5947-32x-rgb-led-board/

[migsantiago]

Nice job.

You could implement it on a motor or something in order to make a propeller colored clock.

[Simon]

will your next versions implement a better mechanical system whereby if you plug them together you get a continuous row of leds instead of a gap between boards ? what sort of software does it require ? will you supply that to whoever buys the boards ?

[JohnS_AZ]

I would certainly take a few.

Do you have a schematic available?  [edit] Never mind, dumb question. It's the driver and leds.
You might want to add some holes for mounting the board.

( BTW ... awesome on the Monk theme.  )

[allanw]

I wrote some software for the Arduino and it's pretty simple. You can just do bit toggling and the 16MHz atmega can update at approximately 250Hz. With floating point math it drops down to 100Hz. I'm going to try using hardware SPI instead which will be much faster. Note that the driver chips are continuously doing their own PWM and there is no flickering.

Simon, yeah, I screwed up the edge connectors too close to the edge. In the next batch of boards I'll make it so that there is no gap when they're connected. Mounting holes are also a good idea.

Actually, the original intent was for this to be a propeller clock but I was never able to figure out how to provide power to the thing while rotating... I've looked at other projects but it seemed complicated to have to modify a motor and I don't know how to really do that.

Also, does anyone have any recommendations for board-to-board edge connectors that preferably lock?

[Simon]

Also, does anyone have any recommendations for board-to-board edge connectors that preferably lock?

well locking no but your standard headers would be good enough as they are thick to carry the power and if the boards are screwed down they can't move anyway, even with locking plugs/sockets I'm guessing that a board that long moving around will have significant leverage so would still be prone to come loose maybe

[ByKa]

It's fantastic!

Can I buying this completted board (with LED's and with TLC5947's)?

ByKa form Hungary.

[allanw]

I made a revision to the board that adds mounting holes, gapless daisy chaining, and a header for external power connection. Then I put in an order for 50x PCB's! Once they arrive in two to three weeks I'll be selling them. Details here:

http://electronoblog.allanw.org/rgb-stick/

Any comments? Pricing seem fair to you guys? I don't want to just purchase cheapo RGB LED's from Ebay and end up with sketchy ones, explaining the price raise. And then I realized my assembly time costs money too

[EEVblog]

And it's got a Flying Spaghetti Monster - AWESOME!

Dave.

[EEVblog]

By coincidence, I'm working on this RGB display design today:







8x8 x 4 RGB displays can be cascaded in horizontal and vertical directions to form larger displays.

Dave.

[Mechatrommer]

i bought similar to this 8x8 led, except its not RGB, its only R. will wait until i'm free, then i will move to this moving/animated text project for my car. nice to have those pictures posted.

[allanw]

That looks pretty good. I'm jealous now Will you be selling bare PCB's/kits?

What's the purpose of cutting out the board in the middle?

Hope yours is a lot cheaper than Sparkfun's $60 single RGB LED matrix/controller board.

[EEVblog]

That looks pretty good. I'm jealous now Will you be selling bare PCB's/kits?

No, it's for a trade show demo.

What's the purpose of cutting out the board in the middle?

Wank factor.
It's got extra GOLD wank on the bottom too, but removed that in the photo to protect the innocent.

Hope yours is a lot cheaper than Sparkfun's $60 single RGB LED matrix/controller board.

It could be, the RGB module is only about $5 or something.

Dave.

[allanw]

It could be, the RGB module is only about $5 or something.

Dave.

Really? The cheapest I've seen was $20. What's the source, if you don't mind sharing?

[JohnS_AZ]

@allanw 

Your board looks great. Pricing is a sticky issue, and one I struggle with a bit. On the one hand $65 feels a little steep, and a little hard to swallow for newcomers who can't scrape together $50 for a decent DMM. On the other hand, if someone asked ME to build those boards for them I'd certainly charge more than that. It's a really tough tightrope to walk; balancing higher price/higher margin/lower volume vs. lower price/lower margin/higher volume. "Price point analysis" seems to me to be equal parts science, art, and wild ass guesses.

I might offer a few suggestions ...

- offer the kit with the cheap eBay LEDs to get the cost down. You might even toss in a couple spares.
- offer a "premium LED" upgrade.
- invert the list on your web page. Put the least expensive option at the top, and the priciest at the bottom.

BTW... offering it as a semi-kit (with the SMT stuff soldered) is a GREAT idea.
(I'm really curious to know how you solder the thermal pad down. )

[allanw]

I found that having a slightly large via would allow you to directly use the soldering iron to flow solder onto the underside of the chip. You just solder on the pins like normal then do the thermal pad. I'm not 100% sure that all of the thermal pad gets the solder though.

I may end up just getting a hot air gun for $100, but my room already has enough electronics, heh.

[JohnS_AZ]

Ahhh.  That's pretty smart. I was guessing some sort of hot-plate reflow process.

[Zad]

The cheapest I can see at the moment are US $122.50 inc P&P for 10 here. http://cgi.ebay.co.uk/Lot-10-RGB-Full-Color-8-8-Dot-Matrix-LED-Display-2-4-/190435228552

I love the reassuring data sheet:
"APPEARANCE: EVRY PART SHOULD BE FINISHED NOT TO EXIST RUST FLAW CRACK AND BAD PLATIONG"

Bless 'em. Note that "should" has very little weight, it needs to be "must" to have any contractual worth.

[Zad]

I have this ongoing project (not really deserving of the name as it has taken 4 years so far) to make one of those Christmas light nets which can be programmed to display text/graphics. Rather than use a standard array, I thought it might be interesting to use an interleaved quincunx array, which in theory gives double the vertical and horizontal resolution. This is a prototype I made to play around with rather than having a huge wall sized thing.



Oh boy, that lot took some soldering!

[Mechatrommer]

I have this ongoing project (not really deserving of the name as it has taken 4 years so far) to make one of those Christmas light nets which can be programmed to display text/graphics.

thats a "hardcore"

[Simon]

I have this ongoing project (not really deserving of the name as it has taken 4 years so far) to make one of those Christmas light nets which can be programmed to display text/graphics. Rather than use a standard array, I thought it might be interesting to use an interleaved quincunx array, which in theory gives double the vertical and horizontal resolution. This is a prototype I made to play around with rather than having a huge wall sized thing.



Oh boy, that lot took some soldering!

reminds me of my 225 UV led exposure box, I feel your achievement, took me eight hours to place and solder

[allanw]

When a board is heavily populated or reworked (say with the help of a hot air gun.....), you often find that the board curves. Two questions:

1) Why does it curve? Is this due to the copper side being unable to return to its original dimensions due to the introduction of added material within the copper plane while heated? Is there some change in the epoxy layer? It seems to happen when many components are (re-) soldered.

2) How do you prevent it? Would a brace/frame during the soldering prevent this effect from taking place?

.o:0|O|0:o.

Were you intending to make a new topic or something?

I think a board warps because the thermal expansion rate of materials on the board is different. When you only heat up one part of the board it'll warp in that area. That said, I haven't ever had problems with this and I've applied way too much heat to FR-4's before. Is your board particularly thin?

You can try using a pre-heater. Either a skillet or hot plate or one of the expensive dedicated PCB preheater units. It bakes the entire board at a nice temperature so that there's less thermal shock when you solder.

[EEVblog]

I have this ongoing project (not really deserving of the name as it has taken 4 years so far) to make one of those Christmas light nets which can be programmed to display text/graphics.

thats a "hardcore"

Nah, THIS is hardcore!
19008 LED's





1.5kg of leftover pins!








Dave.

[Mechatrommer]

thats a "hardcore"

Nah, THIS is hardcore!
19008 LED's
Dave.

Nah! thats different. Thats NUTS!
unless they make money out of it (sell)
looks like they are building score board or something, drag nerds? sporting? soccer? whatever.

ps: to avoid some misunderstanding to others, sometime i refer "hardcore" as somebody who build "passionately" from scratch even if its already readily available easily in the market. the above picture could be a hardcore! after completion, they will have full grasp of the device "working how to's principle". most of the time, its a good thing, given that you have plenty amount of free time and money to invest. Cheers

[Zad]

Jeez that's mad! Any idea what it does, presumably a text/graphic panel? The web site behind it is just an Altair kit forum. A friend of mine built an interactive LED table from 12 or so kit panels, the same panels as this: