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LEDs... more LEDs...we all love LEDs


#1

What is it about LEDs that makes everyone interested?! I have been throwing ideas in my head about what can we do with LEDs for gadgeteer. The first one was LED7R, which is pretty sweet I must say. You have to see it love to appreciate it more :slight_smile: But 7 LEDs is not enough, we want hundreds! But what if someone wanted less, what if wanted more? The answer is, expandable, thanks to dasylink.

I have seen this LoL shield for arduino http://www.sparkfun.com/products/9796 that looked promising but then found this video

This will be no problem as we should plan in making it expandable. You need one, get one, you need more, get multiple. Adding on, the processor may not have enough pin speed to control 1000 LEDs for example plus this will waste the processor time on something basic. This is also solved by the daisylink. The processor will only have to send couple-byte-bitmap of the LED matrix and then the little micro than handles daisylink can also handle the LED scanning.

The LED spacing must be perfect between LEDs and then it has to be the same if you have multiple boards. You could have thousands of LEDs and all should be at the exact same spacing. This can be taken care of by giving the board a shape like puzzle so when you place the board in matrix, they can mount to each other somehow.

One last problem, power! If you have 1000 LEDs, do not expect them to be all powered from the mainboard. Instead this module should have an “optional” way to power from separate power or from the mainboard.

Ok…I am off to design this but wait, what microcontroller to use? using avr is good because of the arduino IDE but then we can get 50mhz ARM processor for less money! Faster processor means faster refresh rate.

Also, will this be done charlieplexing or matrix? Matrix is easier and gives higher refresh rate. Charlieplexing is less power but can be very confusing! http://en.wikipedia.org/wiki/Charlieplexing

As this is another OSH design, you guys are invited to join in.
We need some feedback on, do you want this finished (SMT LEDs) or kit like LoL shield (TH LEDs)?
How many LEDs should be on one module? Remember you can have as many as you like daisylink.
How much do you think such module is worth?
Having RGB or multicolor LEDs is great for sure but will increase the cost much. Is this a must have?


#2

Great idea ! I love leds !
I have experimented a bit with rainbowduino and Fez domino, but found out that netmf was a little to slow, or the rainbowduino firmware not adapted.

Have you seen this one ? https://www.adafruit.com/products/420


#3

Correct but the NETMF processor will not do any refresh. It will send high level command to the little micro that is handling the relatime refresh + daisylink protocol.

No I haven’t.


#4

Gus, count me in if I can help !

For me, RGB is a must. I am working for the kids on a 8x8 RGB led matrix to show a “robot face” with eyes, funny noze and mouth, all moving. I like the rainbowduino board, because you can either have a little square matrix you can daisychain in “puzzle”, or use only the board and connect any kind of led remotly (use the solid state led matrix like this one http://www.seeedstudio.com/depot/60mm-square-88-led-matrix-super-bright-rgb-p-113.html?cPath=163_165 ) or connect any other led to construct a cube kit ( http://www.seeedstudio.com/depot/rainbow-cube-kit-acrylic-harness-p-1021.html ) etc.

However the rainbowduino firmware is just crapy, the I2C protocol not adapted (SPI way better).

A good thing is also the possibility to play with the multiplexing frequency / duty cycle to minimize power usage. 15 years ago I used a long chain of 7 segment displays, and that made a very big difference in power usage to use multiplexing (50/60Hz, like for TVs, the human eye don’t seeing the flickering)


#5

The LoL shield and kin are nice as a kit for learning. Once you’ve progressed a bit with blinky stuff, they quickly become boring, unless you have a project they are specifically suited for. The Adafruit RGB matrix is awesome, but expensive. Something in the middle of these two would be appropriate, or maybe an offering on either end of the spectrum between budget blinkies and dazzling panels.

There’s also a lot to be said for individual RGB LED modules, as well. Something similar to the BlinkM or MaxM idea http://thingm.com/products.html. These can be wired or wireless via IR. Once programmed, they go about their business until the next signal arrives. I’ve wanted to do something like this with Xbee mesh, all controlled from a central uC like a Spider.

Also, the current DaisyLink RGB module offered here is just not bright enough IMHO. I have some that use the WS2801 chip that are $5 in singles and much brighter. Hooked in series to an extender module, I get identical function and much more luminosity at considerably less cost.

Count me in on some blinky design!


#6

Here’s an 8x8 at Evil Mad Science. Those have puzzle-like connectors to keep things aligned

http://evilmadscience.com/component/content/article/241

Pete


#7

@ Pete,

Why does it seem like every time you post something, there’s a direct risk to my wallet from following your link?

There are easily half a dozen things on that site that I want now. I’m gonna have to get another part-time job to finance my habit if you keep this up. :slight_smile:


#8

What about just a PCB offering that would allow the user to solder in either RGB or single color LEDs? The DaisyLink code could automatically determine what it’s capabilities are by what circuits are completed. This could be offered in many different sizes to accommodate 3mm to 10mm LEDs. I like the block style LEDs but they seem very cost prohibitive as far as being able to build a large matrix from them.


#9

I think you would have to have to separate PCBs because of a large difference in routing and resistors between RGB and single colors. They still could be kits to keep cost down.


#10

I think there are some integrated LED drivers with built in resistors that can be used to avoid that


#11

But that doesn’t really matter in a finished PCB though does it? Cost is usually per sq inch regardless of the amount of routing. For a single color you just use one of the three routes and solder in whichever LEDs and resistors you need.


#12

@ devhammer

They have a lot of fun stuff. I have their LED assortment and finally have an eggbot on the way. I’m curious to try decorating an ornament or two :slight_smile:


#13

@ Pete

The EggBot is definitely tempting, but I think if I buy any more tools before I clean up my workshop, I might need to find another place to sleep…and the unfinished basement isn’t my idea of comfy.

That said, I did just order a soldering station and digital multimeter, and a few other odds and ends. I still have my late father’s Simpson meter, but while it has sentimental value, it’s not quite up to the tasks I’ve asked of it lately.

Given that you have an oscilloscope, do you have a recommendation for where to get one inexpensively? I’m trying to decide between that and a logic analyzer…I’m trying to figure out some IR protocols, and I’m not sure which will suit the task better.


#14

@ devhammer

This is not really the subject of this post, but if you have a matter of space in your lab and looking for both a logic analyser and and mixed signal scope, I have seen this one yesterday : http://www.picotech.com/mixed-signal-oscilloscope.html

My father has been using one of the same brand (not this one) for several years and he is very happy with it !

There is even a competition (link http://www.picoscopemso.com/ ) if you want to try to win one :wink: