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DIY Sphero — Parallax Forums

DIY Sphero

ercoerco Posts: 20,256
edited 2014-11-07 14:24 in Robotics
A current project is a DIY Sphero, IR-controlled through a clear ball. Acrylic hemispheres are ridiculously expensive, so I went the other way: a hamster ball. $5 for this 4.5" diameter ball at Petsmart, certainly cheap enough. Just for fun, I also ordered one from Ebay China, which showed up today. $1.61 with free ship! Once again, I am baffled by China shipping policies. Clearly this is a large volume package, a 4.5" diameter sphere with a small wraparound package. I couldn't mail it to my neighbor for $1.61.

Some interesting comparisons between the two, I actually prefer the Chinese ball for this application. I needed to hand drill two holes for an axle in the Petsmart unit, but the China part comes with holes in place. Petsmart unit is crystal clear, China unit is slightly milky. After some wear, the crystal clear unit might show scratches on the rolling surface. Petsmart unit is two hemispheres bonded together, China unit is held together with 4 screws, which means it can be disassembled for building the goodies inside.

More on this situation as it develops.

Comments

  • msrobotsmsrobots Posts: 3,709
    edited 2014-10-30 19:39
    about free? shipping from china.

    International shipping contracts with snail-mail are old. Very old. Hundreds of years old.

    The basic rule is that the delivering country delivers up to the border and the receiving country has to deliver the mail without getting paid for.

    This works in both directions. In theory. Sadly we do not send as much goods from US to china via mail.

    So the free shipping you get from china is actually paid for by the US Mail. They have to deliver the goods but get not paid for. Simple as it is.

    Enjoy!

    Mike
  • Martin_HMartin_H Posts: 4,051
    edited 2014-10-31 06:27
    This has great potential as a project. Can't wait to see some videos.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-10-31 07:05
    msrobots wrote: »
    about free? shipping from china.

    International shipping contracts with snail-mail are old. Very old. Hundreds of years old.

    The basic rule is that the delivering country delivers up to the border and the receiving country has to deliver the mail without getting paid for.

    This works in both directions. In theory. Sadly we do not send as much goods from US to china via mail.

    So the free shipping you get from china is actually paid for by the US Mail. They have to deliver the goods but get not paid for. Simple as it is.

    Enjoy!

    Mike

    Are you sure this is still the case? There was a relatively recent thread stating this policy is no long in effect.

    BTW, I purchased a few of the hamster balls myself. I'm not sure how they will be used yet.
  • ercoerco Posts: 20,256
    edited 2014-10-31 08:01
    Duane Degn wrote: »
    BTW, I purchased a few of the hamster balls myself. I'm not sure how they will be used yet.

    There's always...
  • WhitWhit Posts: 4,191
    edited 2014-10-31 11:03
    @erco - cool sounding project. Can't wait to see your "Sphero!" I love the hamster powered walker! This video showed up on the feed! Another very cool walker - but bi-pedal! Check out the weight shift mechanism...

    [video=youtube_share;0JnTThZMJAg]
  • ercoerco Posts: 20,256
    edited 2014-10-31 11:26
    Yes, Whit, I bought one of those Gakken Bipedal walker kits a while back. $50 for a genuine kit from Japan. No cheap clones yet. Haven't built it yet, savoring the opportunity.

    http://www.ebay.com/itm/Theo-Jansen-method-Biped-Walking-Robot-Kit-by-Gakken-Otona-no-Kagaku-Magazine-/331330275405?pt=Educational_Toys_US&hash=item4d24d2c84d
  • ercoerco Posts: 20,256
    edited 2014-11-01 16:13
    Here's an inside look at a Sphero: http://atmega32-avr.com/how-sphero-works/ It's basically a full differentially-steered (Gordon would lambast me again if I said differential drive) robot inside a ball.

    FWIW, I plan to try something much simpler, a powered axle and a counterweight hanging down, being shifted left & right via a servo to carve turns. Won't turn on a dime and gerbiling might be a problem. But I know that going in. :)
  • ercoerco Posts: 20,256
    edited 2014-11-04 00:36
    Quick prototype build complete. Two HXT900 servos (drive servo modified for continuous rotation) and plenty of superglue. First test (driven by IR remote) is reasonably encouraging. It does gerbil somewhat, which is damped somewhat on carpet. I need to smooth the acceleration and servo routines, they are very jerky now, which increase gerbiling. Also need to add some lead to the hung weight to lower the CG and add stability.

    Turn out these cheap China hamster balls are polyethylene vs. ABS for ones from Petsmart. Works fine, you just need to use coarse sandpaper to rough up any surface needing superglue & kicker to stick to. I'd say that it would be VERY difficult to use the Petsmart one which does not come apart. Lots of fiddling to get the CG shift mechanism inside working properly.

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  • NikosGNikosG Posts: 705
    edited 2014-11-04 05:05
    Erco,
    Awesome project!
    (and not very expensieve!)
  • ratronicratronic Posts: 1,451
    edited 2014-11-04 08:05
    Pretty nice results on your first test drive erco!
  • PublisonPublison Posts: 12,366
    edited 2014-11-04 08:15
    erco, pretty slick. Now you need to get a cat to chase it around.
  • ercoerco Posts: 20,256
    edited 2014-11-04 08:23
    Even better, Speed Racer: the twins just got a hamster, who has a larger 7" ball. Time to pit robot vs rodent!
  • PublisonPublison Posts: 12,366
    edited 2014-11-04 08:29
    erco wrote: »
    Even better, Speed Racer: the twins just got a hamster, who has a larger 7" ball. Time to pit robot vs rodent!

    Hamster figure 8 training in order.
  • mindrobotsmindrobots Posts: 6,506
    edited 2014-11-04 09:50
    This is really cool! (and potentially recreatable!)

    um, could you please define "gerbling" in a sperical robotic sense? I googled but I'm seriously thinking that is NOT what you intended and now I need to go wash my eyes out! (and clean my browser history)
  • ercoerco Posts: 20,256
    edited 2014-11-04 10:13
    Oops, apologies, there are at least two ways to take that. I meant monowheel gerbiling, see http://en.wikipedia.org/wiki/Monowheel#Other_issues

    It's basically when the wheel/ball oscillates significantly differently than the shifted weight.

    Gerbiling shown at 15-18 seconds and 1:05-1:15.
  • ercoerco Posts: 20,256
    edited 2014-11-04 11:39
    Speaking of monowheels, here's a new extreme sport that uses just one wheel.
  • PublisonPublison Posts: 12,366
    edited 2014-11-04 11:48
    erco wrote: »
    Speaking of monowheels, here's a new extreme sport that uses just one wheel.

    WHAT? No BS1 involved!
  • Duane DegnDuane Degn Posts: 10,588
    edited 2014-11-04 12:33
    The Roboni-I erco made me buy also exhibited "gerbiling" characteristics. I tamed the gerbil in my Roboni-I by replacing the controller board with a Propeller Proto Board and programmed the robot to carefully ramp up to speed.

    Unfortunately this was before I made video records of my robot experiments. My Roboni-I is up in the lab with me and I hope to get it going again soon (this time with video).
  • Martin_HMartin_H Posts: 4,051
    edited 2014-11-04 17:12
    I tend to doubt that extreme wheelbarrowing will catch on. But then again I didn't think Facebook and Twitter would either.
  • WhitWhit Posts: 4,191
    edited 2014-11-06 17:53
    @erco - love the extreme wheelbarrowing video!
  • ercoerco Posts: 20,256
    edited 2014-11-06 20:48
    Surely, 'cuz you're our extreme forum priest!
  • ercoerco Posts: 20,256
    edited 2014-11-07 14:24
    I've ordered a few more of these and discovered that some are 3.7" diameter, I didn't look real close. Probably OK for some applications, but the one I used was 4.5" diameter, FYI. That seemed about right.

    Here's a 3.7": http://www.ebay.com/itm/Mini-Pet-Rodent-Mice-Jogging-Hamster-Gerbil-Rat-Play-Plastic-Exercise-Ball-Chic/271643046256

    Here's a 4.5" (doesn't say, but it's the same one I ordered): http://www.ebay.com/itm/351171066318
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