Cautionary Tales of Power

When doing an LED electronics project, there seem to be three big “P”s that have to be tackled:
1. Pixels (which ones, how many, what configuration?),
2. Programming (what do I want, and how can I do that?), and
3. Power (how much, from where, and how do I distribute it?)

And people (by which I mean: perpetual newbies like me) tend to do them in that order: first wire up some pixels, then program them, then figure out how to power it all for real.

And of course, this often leads to a problem where you get stuck between steps 2 and 3, where you have your creation sort of up and running on the lab bench — but now there’s this little problem of how to power it, and you have to go back and rethink and rework other parts of the project to accommodate the power situation.  So it’s worth planning for power from the start — which is easy to say, but hard to do!

What could possibly go wrong? (A list)

So what happens if you don’t plan for power? Well, here are some power problems that I have personally had. How many of these can you diagnose just from the description?  (“Failure to plan” is a nice catch-all phrase here if you get stuck.)

  • Hrm, now how do I get power all the way up there?
  • Gee, that’s a long run of wire… but if I use fat wire, it’ll be expensive and heavy and cumbersome. Nah…
  • I’ll use skinny wire, it’s much cheaper… Hey, why is it only reading 4v at the far end? And does anyone smell something burning?
  • OK, I switched to thicker wire, and I’ll just re-use the power connectors from before. Holy cow now the connectors are getting hot!
  • Fine, I’ll switch to these big thick nonpolarized connectors. Huh, that’s odd, it’s not working now. Does anyone smell something burning?
  • For this other wearable project, I’ll use a simple battery holder and regular alkaline batteries… hey… why are the colors so ‘warm’.. no blue? And now no green, too…
  • OK, switching power to one of those ’emergency phone chargers’ that takes AAs and puts out 5v from a USB socket. Hey! Why are the batteries dying so fast?
  • OK, fine, I’ll switch to this lithium battery pack… hey, it said 5000mAh… so why did it stop powering my 5000ma project after only half an hour?
  • How come my WS2811 project works fine from my computer, but then flickers like crazy when I power it from this cheap USB wall power adapter?
  • For this big outdoor project, I’ll use this big, burly 12V lead-acid marine battery. Hey… how come it won’t hold a full charge after the first time I let the lights go all night?
  • Everything was working fine yesterday, before last night’s rain!
  • Everything was working fine yesterday in the cold and snow, so it should be working fine today now that it’s warming up, right?!
  • I think I’m going to switch microcontrollers.  The old one had a power regulator that could handle 12v input.  Hey… do you smell something burning?
  • Why is this power switch getting hot now? And why is it now totally stuck in the “on” position? And … do you smell something burning… again?

So: Plan For Power.

The lesson to learn here is that for basically any real project, calculate and plan the power first.  Before you wire up any pixels. Before you write any code. Just stop for a minute and think about how much power you’re going to need, and where it has to come from, and where it has to go.

Use on-line calculators that will help you figure out how much power you’re going to need, and what gauge wire you’ll have to use given how long your cable runs are going to be.  I also really like the “LEDstimator” app for iOS to help explore some “what-if” values for things like wire gauge.

And above all else… uh… wait… do you smell something burning?



Fire2012: an open source fire simulation for Arduino and LEDs

I’ve built and programmed a couple of different ‘fire’ simulations for Arduino and LEDs, and I’ve had numerous requests over the years to share the source code.  I’ve always been happy to share my work; the holdup has been that before I share my code for the world to peer at, I like to clean it up a little.  I like to give the code a clean shave and scrub under its fingernails before it steps out onto the wide open Internet where it might have an audience with Her Royal Majesty, The Queen of England.  It could happen.

Anyway, I finally cleaned up the code for one of my simplest and most legible ‘fire’ simulations, and I give it to you, your Majesty, and everyone else, too. Here’s a video of the code in action on a 30-pixel strip of WS2812B LEDs (or maybe WS2811) and an Arduino.  Source code link is below the video.

Full source code is here:  The simulation itself is only about 25 or 30 lines of code.  It uses our (open source) FastLED library to drive the LEDs.

Discussion about the code and how to port it and use it are here on the FastLED discussion group on G+




“Firelight” Lantern

This past January (2013), I created “Firelight”, a lantern that shines with the light of a simulated fire.

The lantern contains over a hundred LEDs, a microcontroller, a battery pack, and custom software.  The software monitors the remaining power in the batteries, and as the voltage slowly runs down, the flames burn lower, finally dying into embers as the batteries die.

I presented the Firelight lantern at the Veracode winter Hackathon, where I lit it, and then gently blew on the coals to kindle a flame.  I’ve had a few requests to build more of these lanterns for other people, and I’m considering it, but haven’t made a decision yet.  More pictures are here.




Travel Tips for Venturing OUT of Black Rock City

So! You’ve decided to take a trip away from Black Rock City!  Here are some tips to keep in mind when traveling away from Home:

Clothing: Make sure to bring enough clothes so that everyone in your group can have some. Among other things, will save you all time later since you won’t have to keep switching.

Stormy Bedroom Eyes

Travel:  A note of caution here! Some vehicles that appear to have extra room for more people may not be giving rides!  We’re not sure exactly why this is, but we’ve had several reports of this.  Always ask for explicit permission before getting into someone else’s vehicle — a friendly “Hi!” and a wave as you climb in may not be enough!  Use your judgement.  Also note that some vehicles may travel faster than 5 M.P.H.

Make sure you are at Burning Man...

Money: Do you remember when you were a child, collecting bits of money here and there, slowly saving up for that one thing you really wanted? Well, money here works the same way, except that you may have to break open your piggy bank a little bit more often.  If it helps, think of every shop, store, restaurant, gas station, bar, and mall that you see as if they were “Arctica”, and what they’re all selling is basically just ice: cool, and maybe useful, but ultimately fleeting and ephemeral. ‘Nuff said.

be 100% happy or receive 100% money back.*

Fire: Make sure to establish a safe perimeter around any burn events that you create.  This goes double for large-scale burns; many people you meet may be new to this form of expression and will greatly benefit from your love and guidance as they participate in the burning of any large-scale structures.  Also, you might want to ask permission from the structure’s owner beforehand, if you can find them easily.

And finally... The Man burns... and we are done.


Returning Home After Your Trip: After you’ve had an exciting jaunt out and about, it’s always good to come back Home, to be with your family and your loved ones.  Have a wonderful trip, and we’ll see you when you get Home again.

Mighty Trojan Warriors!

Yours in flame-