[Noisebridge-discuss] NB Maker Faire table electronics question.

jarrod hicks hicksu at gmail.com
Mon Apr 13 20:24:02 UTC 2015

Thank you Torrie. Thank you John.

That explanation of the capacitors and gif are quite helpful.

The ATX PSU idea is a great one, but I don't have very much clearance in
the interior of the cavity to fit one (>2") so I went ahead and ordered two
separate PSUs that should each fit inside the table. We'll see...

We will begin testing the electronics setup during CHM on 04/20/2015 using
bread boards to see if we are heading in the right direction.

On Mon, Apr 13, 2015 at 9:23 AM, Torrie Fischer <tdfischer at hackerbots.net>

> I don't have much familiarity with WS2812 strips yet, just LPD8806. Those
> are
> the kind that I've installed in the space. I'm totally out of free
> LPD8806s,
> having just recently assembled most of my rolls into two more skylighting
> cells.
> Like Mitch said, you'll want to wire up your capacitors in parallel with
> your
> VCC/GND lines:
> o--VCC-------o
>        |
>      +--- 1000uF
>       ---
>        |
> o--GND-------o
> Electricity doesn't flow through a capacitor. To use the water analogy,
> imagine the capacitor as a section of pipe with an elastic impermeable
> membrane in the middle. Electricity will push up against it resulting in
> the
> membrane storing energy. Once the source is cut off, the membrane starts
> pushing its stored energy back into the system.
> Obligatory gif:
> http://upload.wikimedia.org/wikipedia/commons/c/c1/CapacitorHydraulicAnalogyAnimation.gif
> As a suggestion, you could just use a regular ATX PSU to power the whole
> system instead of two separate boxes. Yellow lines provide +12VDC and red
> provides +5VDC. they're usually very well regulated so you shouldn't need
> to
> worry too much about filter caps. There is a bin in the hack shelves full
> of
> PSUs just waiting to be repurposed for stuff like this :D
> Looking at the physical layout a bit more, I don't think you'll be able to
> get
> an LED strip to lay flat and make those curves. You'll need to snip some
> short
> 1 or 2 LED segments and make a segmented turn. Tedious work, but c'est la
> vie.
> On Sunday, April 12, 2015 02:52:34 AM jarrod hicks wrote:
> > Hello Noisebridge discussers
> >
> > My name is Jarrod and I mostly do woodworking projects at NB. So I am
> very
> > excited to finally be asking an electronics questions to the discussion
> > list. This is in regards to the Maker Faire booth table we're building. I
> > am new to LED/Arduino projects, but want to make sure I get a decent
> setup
> > put together so others can take things further that I can.
> >
> > First, I have drawn a PDF diagram of how I think the electrical system
> > inside the table will go together. Here the location of it on the wiki:
> >
> > noisebridge.net/images/1/1e/Noisebridge_Table_ElectricalDiagram_v1.pdf
> >
> > 1. Does this power scheme make sense, is there a significantly better
> way?
> > I plan on installing over 4 meters of 60/Meter WS2812B strips. My count
> is
> > about 301 light sources (>5m). The documentation I have been reading
> makes
> > it clear that 4m is the max that I can power as a single strip. Based on
> > this I think I can separate the installation into 2 halves. To power
> theses
> > strips I am thinking I can connect them both to a single 5v 20a power
> > supply based on 301 lights x .06A = 18.06A at full white.
> >
> > 2. Should I not use an Arduino Mega 2560 R3 to run this?  I am concerned
> > that this has the headers installed, would this make the wiring difficult
> > or unreliable?
> > I read that the WS2812Bs will take up a fair about of the Arduino's
> memory
> > and that the UNO or Pro Mini with 2k SRAM may not be enough to allow
> > additional "libraries". This doesn't mean much to me yet, but the price
> > difference isn't too bad and I would like for others to be able to make
> > this LED installation do other things in the future, so unless there is a
> > "deal breaker" I am not aware of I will stick with it.
> >
> > 3. This table will be connected to a 120VAC outlet for power. With the 5V
> > 20A LED power supply and the 12v Arduino power supply running, is there
> > still a decent amount of electricity left over from a typical 120VAC
> power
> > outlet to make it worth installing AC power outlets in the table?
> >
> > I plan to buy parts very soon so any help is appreciated. Please let me
> > know if clarification is needed.
> >
> > Cheers.
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