Magic Staff – FAQ and Build Details

Idling staff
Idling

Well I’m back home after taking the staff out for Halloween.  I carried around as part of my costume, costume – greeting people coming to the community for trick or treating, but also to hang out with my neighbors.   A lot of people were asking about the staff – both seeing it in action and having heard about me working on it for the last 2-3 months.

Now, I’m back home, the staff is sitting in the corner, still running.  I’m using this as a battery test.  It’s running the ‘sparkle’ pattern, which everyone agrees is the prettiest (see the video from my previous post).  It’s been on, showing patterns and lights now for about 5 hours, easily surpassing what I expected from the 8 C NiMH cells.

People on Hackaday and people I meet in person ask a lot of questions, so I decided to write up an FAQ….

Lets start with the first one…  “Why did you build this?  Where’d you get the idea?”

It all started with a book…

Continue reading “Magic Staff – FAQ and Build Details”

http://www.overshopping.com

Magic Staff – Takin it out for a spin

Zach and staff
Zach holds the completed staff

The day finally arrived! After a marathon work session on Saturday, I was able to take the staff to a party last night! The batteries held up great, the staff was a great hit, and everyone was asking about it and wanting to see what it did. Talk about inspiring!

There were naturally some ups and downs, with some wins and some losses:

  • WIN: Never. Ever. Underestimate the power of  HOT GLUE.  I solved the ‘solder joints are not strong enough’ problem by embedding the LED strip ends in a few mm of hot glue.  WIN!
  • WIN: By repurposing a shipping container for my son’s new skate wheels, I was able to fashion an enclosure that would hold the Arduino Uno R3 and all the support wiring until my new Arduino Mini 05 arrived.  It gave the staff a ‘navigation light’ look, but the glow of the board lights was sort of nice.
  • WIN: Soldering irons can be used to make holes in plastic.  Shhh, don’t tell anyone.
  • OOPS: I made one major miscalculation.  The battery mounts are custom formed blocks widh hand wound springs for tension.  I put the tension spring on the BOTTOM of the mount, which means the batteries would push down on the spring and disconnect at the slightest bounce.  I’m not looking forward to reworking that section, but this is a learning experience, no?
  • OOPS: I didn’t get a chance to install a power switch, so there’s no ‘off’ state without pulling the cap and disconnecting the power leads.  Oh well.
  • WIN: The batteries lasted much longer than I expected.  The ‘sparkle’ mode draws very little current (the algorithm has one in every 3 LED’s on, and the values it’s using are at 1/4 brightness:
    uint32_t on = strip1.Color(random(64),random(64),random(64));
  • WIN: the coded interrupt routine that uses the button to switch modes works perfectly.  I could change patterns with a quick touch.  I need some more interactive modes, but as a pure display item, total win.
  • WIN? : I totally want to add more features and functions.  A sound sensor so the staff can react to noise / music around it.  A shock sensor (other than the batteries bouncing) so a tap on the floor will cause a ripple function or something.  AN OFF SWITCH.  More interesting patterns.  An external USB port, etc etc.  Many of these things are simple coding updates, but others will require research.

I’ll try and fix the battery tray problem by Halloween, but I think we’re in pretty good shape!

ETA Here’s a video of the staff in action.

Magic Staff – Batteries, load, and runtime

Another few hours of work this weekend saw the Staff cut loose from it’s moorings for the first time.

Staff
Staff running on batteries only for the first time

One of the biggest challenges on this project is power.  The LED strips are 55 tricolor (very bright!) LEDs driven by WS2811 controllers.  The strips are powered at 5v.  Doing some quick load testing on the initial strip (and some online research) showed that each LED has a maximum draw of 60mA, so a 55 LED strip can draw a max of  3.3A @ 5v, and 6 strips can draw something like 20A @ 5v if the entire thing is at full brightness.  That’s a heck of a lot of current.   Compared to that, the Arduino wouldn’t be drawing dink.

I had to balance battery capacity with weight (this thing is meant to be carried in one hand after all).  I considered using D cells, but they’re just too heavy.  I ended up with 8 NiMH C batteries ( http://www.amazon.com/gp/product/B001AX1UQO/ ) from Tenergy.  These are ranked at 5000 mAh @ 1.5v.  I ganged them in groups of 4, connected in parallel.  This gave me 5Ah per group, or 10Ah total.  With a draw of 20A, at full power, it works out to only half an hour of uptime.  Now, there’s a lot of loss in this as well, so realistically, at full power (255,255,255 values on all the LEDs) I expect to get only about 15-20 minutes of use.

In general use, I don’t plan on using this in BLAZING WHITE MODE for more than a few seconds at any given time, but ongoing running will run the batteries down.  The other night I ran the staff using a ‘randomized’ pattern for a good 15 minutes on those batteries without any ill effects, and saw no problems (Check out the video here:  http://youtu.be/LNbIwpk5vdA )

Magic Staff Update – First time off-laptop

LED Soldering
My first surface-soldering attempt to attach the LED strips

Well, the magic staff project has reached a pretty awesome milestone.

Last night was the first time I had the entire assembly operating off-computer.  The Arduino Uno had been running directly via USB cable from my mac.  That provided power and an easy way to upload code.  With my new bench power supply, I had enough amps in the bench supply to power the LEDs and the Uno.  A few alligator clips later, and voila, the staff had 3 led strips lit, and the Uno was running it’s program just fine.

I also detached and remounted the 2 strips that were mounted backwards (yes, these strips are directional.  See the arrow?  Yeah, missed that on the first run – Of the 6 LED strips, 2 were backwards.  Oh well).  Peeling them off wasn’t that hard – hot glue doesn’t hold up to lateral forces, and it came away easily.

These strips come with one end of the cable pre-wired with power and data, so I only had to manually solder the parts that were ‘cut’ in the middle of the strand.  That was only 3 connections, so it wasn’t so bad.  But I’ll admit, not having to do all six was a relief.

power and data hookups
“Hookup” end of the staff – Power and data connections are here.

So.  Things are reassembled now, all the ground and +5V lines are attached (and ganged together), and data lines are wired to all the strips.  I need to come up with a strain relief mechanism to avoid yanking the leads off the strips, and then work on how to install the controller, power leads, and hookups into the head of the staff.

Oh, I also ordered the 8 C cell NiMH batteries I’ll be using.  They should be in today.

Getting there!