My 32x RGB LED board - Page 1
Forum section: electronics / projects

author: allanw
author_rank: Frequent Contributor
timestamp: October 10, 2010, 06:05:40 am
content: 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/

author: migsantiago
author_rank: Frequent Contributor
timestamp: October 10, 2010, 02:11:41 pm
content: Nice job.You could implement it on a motor or something in order to make a propeller colored clock.

author: Simon
author_rank: Unknown
timestamp: October 10, 2010, 02:56:14 pm
content: 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 ?

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: October 10, 2010, 04:08:30 pm
content: I would certainly take a few.Do you have a schematic available?  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.)

author: allanw
author_rank: Frequent Contributor
timestamp: October 10, 2010, 07:07:17 pm
content: 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?

author: Simon
author_rank: Unknown
timestamp: October 10, 2010, 08:42:30 pm
content: Quote from: allanw on October 10, 2010, 07:07:17 pmwell 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

author: ByKa
author_rank: Newbie
timestamp: October 17, 2010, 03:31:56 pm
content: It's fantastic!Can I buying this completted board (with LED's and with TLC5947's)?ByKa form Hungary.

author: allanw
author_rank: Frequent Contributor
timestamp: November 01, 2010, 02:43:15 am
content: 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

author: EEVblog
author_rank: Unknown
timestamp: November 01, 2010, 03:56:23 am
content: And it's got a Flying Spaghetti Monster - AWESOME!Dave.

author: EEVblog
author_rank: Unknown
timestamp: November 01, 2010, 04:09:22 am
content: 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.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 01, 2010, 04:14:26 am
content: 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.

author: allanw
author_rank: Frequent Contributor
timestamp: November 01, 2010, 04:18:34 am
content: That looks pretty good. I'm jealous nowWill 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.

author: EEVblog
author_rank: Unknown
timestamp: November 01, 2010, 05:35:24 am
content: Quote from: allanw on November 01, 2010, 04:18:34 amNo, it's for a trade show demo.QuoteWank factor.It's got extra GOLD wank on the bottom too, but removed that in the photo to protect the innocent.QuoteIt could be, the RGB module is only about $5 or something.Dave.

author: allanw
author_rank: Frequent Contributor
timestamp: November 01, 2010, 05:59:26 am
content: Quote from: EEVblog on November 01, 2010, 05:35:24 amReally? The cheapest I've seen was $20. What's the source, if you don't mind sharing?

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 01, 2010, 04:13:33 pm
content: @allanwYour 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.)

author: allanw
author_rank: Frequent Contributor
timestamp: November 01, 2010, 04:53:13 pm
content: 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.

author: JohnS_AZ
author_rank: Frequent Contributor
timestamp: November 01, 2010, 05:11:20 pm
content: Ahhh. That's pretty smart. I was guessing some sort of hot-plate reflow process.

author: Zad
author_rank: Super Contributor
timestamp: November 01, 2010, 06:19:54 pm
content: 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-/190435228552I 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.

author: Zad
author_rank: Super Contributor
timestamp: November 01, 2010, 11:26:09 pm
content: 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!

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 02, 2010, 07:27:44 am
content: Quote from: Zad on November 01, 2010, 11:26:09 pmthats a "hardcore"

author: Simon
author_rank: Unknown
timestamp: November 02, 2010, 09:18:12 am
content: Quote from: Zad on November 01, 2010, 11:26:09 pmreminds me of my 225 UV led exposure box, I feel your achievement, took me eight hours to place and solder

author: allanw
author_rank: Frequent Contributor
timestamp: November 02, 2010, 04:09:34 pm
content: Quote from: .o:0|O|0:o. on November 02, 2010, 07:55:26 amWere 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.

author: EEVblog
author_rank: Unknown
timestamp: November 03, 2010, 12:09:33 am
content: Quote from: shafri on November 02, 2010, 07:27:44 amNah, THIS is hardcore!19008 LED's1.5kg of leftover pins!Dave.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 03, 2010, 06:25:20 am
content: Quote from: EEVblog on November 03, 2010, 12:09:33 amNah! 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

author: Zad
author_rank: Super Contributor
timestamp: November 04, 2010, 12:13:04 am
content: 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:

author: EEVblog
author_rank: Unknown
timestamp: November 04, 2010, 01:53:41 am
content: Quote from: Zad on November 04, 2010, 12:13:04 amThe guy bought 50,000 LEDs on ebay and wanted to do something with them.He called it the "wall of RAM", so had some idea of making it mimic the RAM contents on his Altair or something.Never saw photos or video of it actually working.It was on sci.electronics.basics quite a few years back.Dave.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 04, 2010, 02:58:17 am
content: dont know how much driver ic's they are going to need for that. looking at the LEDs alone is mad, i think the driver circuit will be just as worst.i just dont have enough time for those. so i just purchase preassembled matrix from sureelectronics ebay, totalling 1000+ leds, including the ic's and shiiping cost me about $50. i have another 100+ bare 5mm leds incl resistor that cost me somewhere near $10. not RGB though.

author: Simon
author_rank: Unknown
timestamp: November 04, 2010, 07:59:01 am
content: Quote from: Zad on November 04, 2010, 12:13:04 amI must make one of these one day, I have a coffee table frame with no glass ready to take it

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 04, 2010, 01:04:57 pm
content: Quote from: Simon on November 04, 2010, 07:59:01 ammake sure you have your co-workers in, otherwise, u'll have a lot of headache!

author: Simon
author_rank: Unknown
timestamp: November 04, 2010, 01:16:47 pm
content: why ?

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 04, 2010, 02:53:32 pm
content: Quote from: Simon on November 04, 2010, 01:16:47 pmdo it then u'll know. as a general rule, there is no easy way to become a great man, but, who knows... you maybe the one!i thought you were talking about the 19K LEDs panel

author: Simon
author_rank: Unknown
timestamp: November 04, 2010, 03:44:40 pm
content: nah just the water ripple effect table, that's and awsome effect

author: EEVblog
author_rank: Unknown
timestamp: November 05, 2010, 12:38:13 am
content: The completed RGB display panel with 4 x 1x4 RGB modules on custom smoked perspex stand (funky laser cut name removed to protect the innocent), ready for the trade show display.Total turn-around time including module board design and manufacture, custom display stand, assembly (DaveCAD assembly services), and design debug and mods - less than a week.Dave.

author: .o:0|O|0:o.
author_rank: Regular Contributor
timestamp: November 05, 2010, 04:53:00 am
content: Less than a week... That's incredible!I would be interested in seeing more photos or a demo. Have you programmed anything interesting into it yet?.o:0|O|0:o.

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 05, 2010, 07:55:57 am
content: Quote from: .o:0|O|0:o. on November 05, 2010, 04:53:00 amyou must be a great man to be able to do that, and as i said earlier, its not an easy path. Dave is known to have built something more complex than that. this leds thing is just a toy to him

author: EEVblog
author_rank: Unknown
timestamp: November 05, 2010, 09:11:10 am
content: Quote from: shafri on November 05, 2010, 07:55:57 amIt can be just as big a pain in the arse as a system 100 times as big and complex!Dave.

author: Simon
author_rank: Unknown
timestamp: November 05, 2010, 09:37:20 am
content: I expect that in principle it is simple, it is the logistics of so many units all being controlled at the same time

author: adam1213
author_rank: Regular Contributor
timestamp: November 05, 2010, 10:50:35 am
content: Quote from: EEVblog on November 01, 2010, 04:09:22 amwhat controller(s) are you using?video cases are a convenient size to use as case for some dot matrix displays

author: Mechatrommer
author_rank: Super Contributor
timestamp: November 05, 2010, 11:10:21 am
content: Quote from: EEVblog on November 05, 2010, 12:38:13 ami just noticed this, i thought its some highly specialized professional assembling service, but.... when looking carefully at the name... it is indeed!

author: DJPhil
author_rank: Frequent Contributor
timestamp: November 06, 2010, 11:15:50 am
content: Quote from: shafri on November 05, 2010, 11:10:21 amI still have a copy of DaveCAD from one of the earlier videos.

author: Zad
author_rank: Super Contributor
timestamp: November 09, 2010, 04:36:01 pm
content: Following on from this (and the latest Amp Hour Blog) I saw this on Hacked Gadgets today.Not exactly pro, but cool nevertheless. I'm surprised the micro has enough horsepower to refresh all those LEDs without flicker or tearing. Which reminds me of a couple of educational blog entries I keep meaning to write. Much respect to all those bloggers who can somehow make time to create what seems like dozens of articles a week!

author: abbtech
author_rank: Contributor
timestamp: November 10, 2010, 06:54:23 am
content: Quote from: EEVblog on November 03, 2010, 12:09:33 amI feel tired just thinking about soldering all those connections!

author: allanw
author_rank: Frequent Contributor
timestamp: November 11, 2010, 10:08:12 am
content: Thanks for mentioning this on hackedgadgets.com. Actually getting some traffic now

author: allanw
author_rank: Frequent Contributor
timestamp: November 11, 2010, 09:41:26 pm
content: Got the boards from pcbcart. They look pretty good:

author: abbtech
author_rank: Contributor
timestamp: November 12, 2010, 01:48:01 am
content: Those boards looks great. There is something really sexy about the black solder mask with white silk screen. I went with the same combo on this board and I love the way it came out (also done at PCBCart).http://alan-parekh.vstore.ca/gear-clock-circuit-board-p-106.html

author: FreeThinker
author_rank: Frequent Contributor
timestamp: November 12, 2010, 08:21:22 am
content: You've got a long way to go to beat this!http://www.elektor.com/news/5-8-million-leds-create-an-image-of-mount-fuji.1601943.lynkx?utm_source=UK&utm_medium=email&utm_campaign=news.Now that's some LED display!

author: ddrl46
author_rank: Regular Contributor
timestamp: November 12, 2010, 12:06:44 pm
content: You should never buy anything from sparkfun, they ask about twice or sometimes even 4 times the price of the same product somewhere else.

author: aerohoff
author_rank: Newbie
timestamp: November 12, 2010, 08:31:31 pm
content: Yeah, you should only buy directly from china or walmartI saw Dave's display at the Arm Techcon this week. If I'd realized Dave was behind it, I'd have spent more time getting to know them. They broke the board right at the beginning of their presentation, and the engineer type had to scramble to fix it while the marketing type started the presentation. Fun times.

author: vaneenbergen
author_rank: Contributor
timestamp: November 12, 2010, 09:06:19 pm
content: hi allthis is my led hobby board i madeduring the first testhttp://video.google.nl/videoplay?docid=843568223430970219#these are 1500 panels with 16 rgb's each.all controlled by 10/100mbit ethernet and rs485.i made this as a hobby/test project to test my network equipment that i develop for lighting control of big shows.joost van eenbergen

author: abbtech
author_rank: Contributor
timestamp: November 12, 2010, 11:24:31 pm
content: Quote from: vaneenbergen on November 12, 2010, 09:06:19 pmWow that is a cool looking project. Is there a write up on it somewhere?Alan

author: vaneenbergen
author_rank: Contributor
timestamp: November 15, 2010, 09:54:24 am
content: Hihere's a picture of the board (attached, i don't know how to add the picture)On the back there are 2 RJ45 connectors with 48V power and RS485 on it.the RS485 is used for the DMX512 communication (lighting control standard)the led control is by TLC5941, at 3kHz refresh and 12 bitthe micro is an arm7 AT91SAM7S128the boards are made on my own SMD pick and place (FLX2010V by essemtec),board being made is our own 10/100mBit ethernet switchi'm getting a new one in january (fast 4 head paraquda)joost

author: allanw
author_rank: Frequent Contributor
timestamp: November 15, 2010, 07:43:35 pm
content: That's some professional stuff. How long does it take to design a huge project like that?

author: vaneenbergen
author_rank: Contributor
timestamp: November 15, 2010, 08:03:04 pm
content: not too longalot of software i allready writing for other products.2 weeks for prototyping.production of 1500 panels took 2 weeks with 2 persons.joost