Running 2 Amps of LEDs through an Arduino Nano

The Arduino Nano provides up to 0.5 Amps of regulated +5v output, on it’s “+5V” pin, which can drive between 10-30 addressable LEDs, depending on your chosen brightness and animation patterns.  Even if you connect a 2 Amp USB power supply (e.g. an iPad charger), the Nano’s little voltage regulator will overheat if you try to draw more than 0.5 Amps from the “+5V” pin on the Arduino.

However, you can ‘tap’ the pre-voltage-regulator power traces on the Nano’s circuit board, and drive 2 Amps of LEDs (over 100) ‘through’ the Nano, and do it in a way that keeps your wiring simple.  Basically, you can find the places on the Nano’s board where the raw USB power connections are exposed, and tap into them there.


But, OK, if you wish to continue…

1. Flip the Nano over so you’re looking at the bottom side.

Two Amp Arduino Nano

2. The unfiltered, unregulated +5 signal from the USB port is available on the board near the base of the D2 pin.  Carefully solder a wire (red, for +5v) directly to the exposed component pin on the circuit board.

3. A convenient companion GND connection can found on the center pin of the power regulator itself.  Solder a wire (black, for ground) to this pin.

4. By powering your LEDs from these direct-power traces (and thus directly from the USB power source), instead of through the Nano’s half-amp-max voltage regulator, you can drive up to about two Amps worth of LEDs, provided that you plug the Nano into a 2 Amp USB power adapter.

I’ve used this technique in probably six or eight Arduino Nano projects, and nothing’s caught fire (yet).  With a little probing around, you can also find similar ‘hacks’ for other models of Arduino, e.g., the Uno, Leonardo, etc., but since power is handled differently on each board, you’ll have to figure it out differently for each board design.

Good luck!


Hoop skirt — made with real hoops!

Eleanor and I spent this weekend working on her Halloween costume.  Part of what she planned was a ‘hoop skirt’, but as you can imagine no commercially available hoop skirt met her exacting standards of design and quality — and also my exacting budgetary requirements.  Naturally, we decided to take the DIY route!  And, we pondered, what goes into a hoop skirt? HOOPS, obviously!

We picked up a used dress at The Garment District (our local vintage/costume/cheapo clothing mecca), a set of three hula-hoops, and some leopard-print duct tape.  The smallest hula hoop became the bottom (largest) hoop for the skirt; the other two had to be dramatically resized smaller (via pliers, dremel, duct tape).  We started construction from the waist down, with a nylon web belt with a parachute snap buckle.  From there, we hung each hoop with repositionable blue painters tape, and balanced each one until it was level.  Then Eleanor secured each hoop in place at the right height with duct tape.

And presto! A hoop skirt made with real hoops! (and duct tape, of course!)

Hoop skirt -- made with real hoops!

“Five Elements” light sculpture

After months of work, “Five Elements”, my first full light sculpture debuted this weekend at a private event.  This quick video shows a short clip of each ‘element’; the actual five-element cycle is 12 minutes long, repeating each of the five elements five times each hour.  As with any “version 1.0”, I have a dozen ways I’d like to polish and keep improving it, but I’m happy with it as is, too.

It’s illuminated by 150 RGB LEDs and controlled by an Arduino Uno using the FastSPI_LED library and my own custom code.
The installation at the debut event used a very different diffuser which made the LEDs more visible.  While both were good, I think I prefer this diffuser overall.

Small Scale Solar power presentation

I gave a “learning lunch” presentation on Small Scale Solar power today.  We had a great audience, got great questions, and had fun doing it — despite the definite lack of sunshine to play with today.

The Short Version is this:

  1. Hook a solar panel to a charge controller to a battery.  (There are starter kits with everything.)
  2. Presto: 12 Volt DC power!
  3. Use your newfound power as-is, or step down to 5v USB, or up to 120VAC using an inverter.

60 Watts of solar panels

The slides don’t tell the whole story by themselves; that requires my own personal song and dance routine.  Nevertheless, here they are, with “lite” graphics for fast download: PDF.

Ice cream no longer requires adult supervision

On the sunny afternoon of Sunday, April 29, 2012, Eleanor, Abby, and a friend, all age 9, walked half a mile to The Chilly Cow for ice cream, and then back again (with a stop at the library, of course) without adult supervision or accompaniment. Total round-trip time was slightly more than an hour, well under the contractually pre-negotiated 90 minutes.

The adventurers’ parents spent the intervening time in various degrees of distraction, ranging from mindful confidence to … less meditative states.  Overall the experience was deemed a great success all around, and at least two of the parents in question got a little choked up for a moment over the “our kids are growing up” factor.

The trip itself was a little less than a half-mile each way, as the crow walks. If you’re a grownup, or driving, or both, you might think of this particular half-mile trip something sort of like this:

Chilly Cow by car

But if you’re walking, it’s more like this (please do click the image to get the full experience) :

Chill Cow on foot

But actually, I think that if you’re 9 years old, and you’re doing this by yourself for the very first time ever, it has nothing to do with time, or space, or distance, or any kind of map at all.  It’s just pure, undiluted awesome.  And that is exactly how it was reported afterwards.

Rejuvenating solar garden lights — with nail polish!

Solar LED garden lights are everywhere these days, and by ‘everywhere’ I mean ‘in our yard.’  We’ve had some for a few years now, and simply through exposure to the elements, the plastic that covers the solar cells becomes so opaque that only a small amount of light gets to them any more.  With the solar cells deprived of even that meager light that we get in Massachusetts in the winter, the solar cells don’t recharge the battery, the battery doesn’t power the LED, the LED doesn’t light up, and our yard has a serious bling deficiency.  Eleanor and I took our solar garden lights inside to see if we could make them bright again somehow.

My first thought when confronting the frosted-over plastic was to try to ‘polish’ it with a fine-grit sandpaper.  I had 400-grit handy and tried it on one cell, the bottom one in this picture.  The top shows how weathered the cells were to start.

Solar garden lights, all 'frosted' over

The sanding helped a little.  Then I rinsed the sanded plastic dust off with water in the sink, and while it was wet it looked great, but as it dried it became frosted and opaque again.  Thinking that perhaps we could use a mild plastic solvent to ‘polish’ the rough surface, I dabbed the solar cells with acetone, but again, as soon as it dried, the surface went from clear to cloudy again.  “We need some way to keep it ‘looking wet’ even when it’s dry,” I mused.  Eleanor got a wide-eyed LIGHTBULB! look in her eyes, and grabbed a bottle of clear nail polish!  She applied a few test swatches.

Nail polish on solar cells?

The nail polish made the weathered old solar cells crystal clear again!  I held the lights while Eleanor applied an even coat of nail polish to all the solar cells.  It really didn’t matter whether the cells had been sanded or not, so we didn’t bother.

Using nail polish to rejuvinate solar cells

A few minutes later, the polish was dry, and we planted the lights outside again.  You can see how completely clear the solar cells are.  Our only concern was that the nail polish might block the UV light that provides a good portion of the solar energy to the cells.

Rejuvinated solar cells soaking up sunlight

We waited for twilight to fall, and when we checked the lights: success!

Fully-recharged solar light glowing brightly!

Even though it was mid-February the solar cells were now getting enough light to make the LEDs glow brightly!  The solar cell rejuvenation project was a total success, and once we figured out how to make the cells ‘clear’ again, it was a quick and easy.

So what did we learn? We learned that ‘frosted’ plastic reflects precious light away from the solar cells; clean, clear solar cells can capture much more light.  Clear nail polish is perfect for rejuvenating plastic-covered solar cells that have become weathered and dull. Some of the solar garden lights they sell have glass covers, and we speculated that they probably (1) are much more resistant to weathering, and (2) probably should be ‘cleaned’ differently from the plastic ones.  Sometimes you need to try one thing to find out what you need to try next.  Sometimes restating the problem out loud to someone else can give them new ideas.  During the dim, dark Massachusetts winter, having bright, cheery little lights in the yard is great.