Welcome home

Finally some pictures.  We had an unfortunate incident, however.  Isaac was doing a great job video’ing us all week.  The camera went missing at the end of the week.  Arg!  We’re all hoping it makes itself known soon.  All we have are some pictures people took on the side.  Thank you all for enjoying to project so much!  It was a lot of fun and incredibly rewarding to share it with everyone.

I’m back!

Sorry for the absence.  We were in Colombia for the last couple of weeks.  Incredible trip.  Kids did amazing.  Travelled around quite a bit and saw a lot of new stuff.  Medellin was incredible.  Pics

Assembly has gone into full swing.  Chuck and Leo were over last night soldering computers.  Got a lot done and most of the heavy lifting is out of the way.  Ponoko and OshPark came through again (as they always do) and my custom boards and housings were waiting for me when we got home.

One thing that I’ve been thinking about is how to configure the XBee radios using my Mac (which will be on playa).  Digi only provides a Windows application.  Wine to the rescue (still amazed with the resources out there).  C++Etc has a great write up on how to use the Windows emulator Wine to run the X-CTU app on the Mac.  I have it installed and running and will test it out tonight.

Leo’s going to have his family running on a separate network at Burningman so we’re working through the logistics of an additional iPhone (and a backup for me).  It will be a good test of the documentation I posted early in the project.

More building

Emil and Beth came over today to do some building.  It was fun to get rolling on more vests.  More motivating than ever to see people diving in.  Updated some of the instructable to reflect some of the new techniques.  Using a razor instead of scissors, how much fur to use.

SFMOMA video

Here’s some video from the SFMOMA show.  Terri’s band is putting together a video which will hopefully have some better quality video.  We ended up putting some LED strands in the boxes that the models were standing on.  It was a cool effect to the them changing alongside the vest.


Boards are in!

The boards from OshPark came in today.  Needless to say, I was very excited.  So here’s the timeline for the order:

  • June 13 – Order placed
  • June 14 – Assigned to panel email received
  • June 15 – Panel sent to panel email received
  • June 26 – Panel received from fab email received
  • July 1 – Order shipped email received
  • July 6 – Order received
OshPark is really a revolution for hobbyists.  The boards are really slick.  Purple, with silkscreen and solder mask.  The fact that we can just update Eagle files is fantastic.  Eagle a full fledged design tool (for what we need) and OshPark produces very nice renderings of what you should expect.
I proceeded to solder up the project immediately.  Thankfully, I’ve had enough failures in this arena to be careful about powering anything up.  Fortunately, I did an alright job of designing the board.  Worked great and was able to program the installed Arduino right away.  I have my list of redesign items but am very pleased by the progress.  Now I just need to get moving on getting the Eagle files generated and uploaded.
The picture below shows the progression.  On the left is the original design with the Arduino Pro.  Granted it has the protective plastic casing which makes it look bigger.  In the middle is the new board before cleanup.  On the right is the new board with components mounted.  I added full female headers on this prototype to allow me to deal with failures.  Once I’m comfortable with the design I’ll remove them and mount the components directly which should halve the thickness of the package.  This should make the whole piece much more wearable.  Additionally this design will include a microphone for the audio active patterns.  You can see the microphone package in the upper right of the picture.

BTW, I have the top hat design coming along.  It’s cycling through some patterns in front of me right now.  More later.

Auto Shutoff

One thing that’s been bothering me for the last couple of months is the cost of the batteries.  They’re not cheap and they can be easily damaged if you let their voltage drop too low.  That’s the main reason that I added the voltage monitoring to the member heartbeat message was so that I could watch it on the iPhone.  I added some code to shut the lights down if the voltage drops too low.  What I didn’t realize is that even with the lights off, the Arduino’s voltage regulator is eating up a fair amount of current.  We accidentally left a couple of batteries connected for a couple of days. Killed the batteries and I ended up with two expensive, explosive bricks.

So the idea was to find away of shutting power to the whole system in some way.  Randy helped me work through some ideas of how to do this with MOSFETs that would use an output pin from the Arduino to control the battery’s access to the circuit.  There would be a power up momentary button that you would hold down until the Arduino had a chance to boot up and set the power up pin connected to the MOSFET.  Once the Arduino detected an under voltage, it would set the pin low, thereby cutting off power to itself (suicide).

We tried to do it ourselves but were having trouble with current being drawn from the pin and causing the MOSFET to power up.  He found this.  We were missing a second MOSFET that helps isolate the Arduino.  Quick trip to Fry’s to get a p-channel MOSFET and we were in business.  In the video, you’ll see that the button press starts up the Arduino.  The power pin status is shown by the yellow on board LED.  Once that LED lights up I can let go of the switch and the system stays on.  After 5 seconds the program sets that pin low and the system shuts down.  Now to test it with the larger system.


Instructable, etc.

Chuck and I finished most of his vest today.  We documented the steps in an instructable (my first!).  I think we covered what we needed to.  The vest looks good and I’m looking forward to seeing more built up.

Still waiting for the boards but I’ve had some luck with software.  I’m diving into the spatial group detection, sound activation and hands off animation.  It’s working pretty well on all fronts.  The biggest issue I’ll have is with the spacial group detection.  Some of the steps needed to get a reasonable graph are expensive to perform in the network (on the order of  seconds).  May be ok but could make the dynamic aspect of group detection more difficult.  Sound is looking good, animation is looking good.

More lessons

So I already have some updates to the board that I need to do.  As it turns out, we wanted to show some friends the vests.  Fun!  Easy to put together and run.  We forgot to disconnect the LiPo batteries afterwards and they drained down to 1V.  Ugh.  Dead.  2 batteries lost.

I need to implement some kind of under-volt protection on the Arduino because I know that it’s going to be difficult to have people remember to take care of all of this late night out in the desert.  Logistically we can help with how we set up camp but I think there needs to be some kind of hardware / software solution to this.  Can a MOSFET handle the 3A.  Probably but need to experiment.  Even so, will the Arduino draw a low enough current for us to last through the night / morning?  Probably but need to experiment.

Also, Chuck’s been over for the last couple of night’s building up his vest.  We’ve been documenting as much as possible for an instructables.com presentation.  Working on that now and hoping to have a full version soon.

Things have changed

I haven’t had custom boards built in a while.  I was going to go with the old standby but I found http://oshpark.com/.  Super cheap and imported Eagle files directly.  We’ll see how it goes but it’s amazing to me how quickly (~2 hours) I was able to build up the board and send it off for fab.  Sparkfun definitely helped with their tutorial on Eagle.  Not only is oshpark cheap, and from what I hear quick, their boards are fab’d in purple!

Here is the first version of the board.  I’m sure there will be mistakes and revisions but a first version in an afternoon is unbelievable.

This configuration will use the Arduino Pro Mini as the platform and will greatly reduce the size of the wearable hardware.  The radio and computer will now be housed on the vest between the shoulder blades.  The benefits will be: higher radio antenna for more range, less weight, easier construction & no need for a utility belt.