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.  https://itunes.apple.com/us/app/ledstimator/id945794010?mt=8

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

 

Advertisements

If I’m confused, it must be playtime.

Some things we try because we have a clear idea where we want to be and a clear idea how to get there.

Some things we try because we’re suddenly shocked to find that the heretofore completely impossible has suddenly and surprisingly come within practical reach.

And some things we try just to play, and to explore what if. We start with our heads full of simple ideas that turn out to be wrong, and we awkwardly replace them in torn out bunches with new confused half-understandings that, later, will let us reach something wholly unexpected.

I’m not sure which of these things in doing here, which means it’s probably that last one.

20140320-090628.jpg


Glowing bubbles?! Yes! …but no.

The other day I was in the store and my attention was caught by “Super Miracle Bubbles® GLOW FUSION™ Bubble Solution” — bubble soap that claimed that it made bubbles that glowed.  These were not bubbles that glowed-under-black-light (fluorescent), not bubbles that glowed-in-the-dark (phosphorescent), but actually bubbles that glowed-of-their-own-accord (chemiluminescent), or so the package claimed.  $3.99 later, I was the proud owner of a bottle of this magic elixir.

Later that night, well after dark, Rosa and I carefully followed the instructions, adding the two included packets of “activator A” and “activator B” to the bubble soap, and stirring (not shaking!) for a minute.  Lo and behold, the little bottle began to glow bright orange, like the innards of a glow stick!

Excited, we dipped the wand in the glowing solution, and blew some bubbles!  In the cold, dark, winter night, they looked like this:

…nothing.  Blackness.

We tried and tried, and sure enough, after a while from the right angle, for a fleeting second, you could see that the bubbles had a tiny glim of light.  But in practice, the drips of bubble solution that fell on the ground far outshone the bubbles themselves, and the full bottle itself was the brightest thing around.  There was no hope of getting enough light out of it to photograph them.

The directions (inside the package!) point all this out.  They tell you to cover the (clear) bottle with black tape or a black bag, and to let your eyes fully adjust to the dark to see the glowing bubbles.  Any other nearby light will drown out the few photons escaping from the bubbles themselves.  Also of note: the instructions repeat several times that these are for outdoor use only.

So, do they glow?  Technically, yes.  Practically, no.  You cannot get a good, satisfying, “glowing bubble” from this bubble solution.  On the other hand, it is pretty nifty to have a bottle of bubble solution that’s glowing in your hand while you’re blowing bubbles.  Fun?  Kinda.  Worth $3.99?  Not for regular use.  Worth trying once?  Yep, and I’m glad we did.

-Mark

Updated April 4, 2012: Here’s a video of some Occupy folks experimenting with adding the contents of a chemical glow stick to some bubble soap.  They got more or less the same results I did, but by a different route.  Clearly, we need some SUPER glow chemicals…