Thursday, February 24, 2011

TOBL: It's Working.

It's working, it's working. It = TOBL and here are some stats:
  • 6 wheels
  • 18 gears (think about it...)
  • 84 oz/in Torque
  • iPhone-controlled via TouchOSC app interface
  • OSC/Serial communication
  • 8 zip-ties
  • Top speed of 0.413 mph (my personal favorite)
After much adieu, TOBL has been captured on film with my new camera -a Pansonic Lumix DMC-ZS7. It's about to make this blog a whole mess snazzier, 9.1 megapixels more snazzy to be exact. Henceforth, all videos shall be shot in 720p HD, like this one (fast-forward to 2:34 for wall flips):

Kind of dark but I still recommend watching in 720p.

Now held together by 8 zip-ties, thats 4X as strong as last time!

One of the finishing touches on TOBL was trimming the servos. However, PWMShield V1.0 is not yet wirelessly-updateable and in the monotony of disconnecting and reconnecting all the controls hardware, I vaporized yet another trace. This board should be renamed "GhettoShield" after all the loose wires I've had to solder to busted traces. The circuit works fine though, and using it saves $33. After fixing the trace the servos were trimmed.

Can you spot the latest exo-trace?

I don't talk about software very often, and that's because I don't know much about it. I do like to share the code I use though, isn't that the point of the whole open-source movement? After all, most of the communication software for TOBL was "taken" from this iPhone-controlled tank and this SFE tutorial (Thanks to both!). I modified bits of this software and wrote the rest to interface this existing code with my TouchOSC layout and electronics. In order to return the favor here is the Arduino and Processing code. You'd think a wireless iPhone-controlled robot would have denser code than ardWINDo, but take a look, it's surprisingly compact.

This project was a lot of fun. It's rare that you can take an idea and bring it into fruition exactly the way you imagined it. My initial goals were to make it iPhone-controlled and able to drive after rolling over -TOBL does both of those things. It wasn't cheap, I would estimate ~$250 including redundancies, but TOBL is an awesomely fun desk toy and an even better platform for playing with software, different sensors, and whatever else.

I also learned that servos are great for being servos, but not so great at being drive motors (especially modified micro-servos). For future projects I will venture down the new and exciting road of custom motor-controllers. Time to start playing with H-bridges...

Wednesday, February 2, 2011

TOBL: Testing

Done with my first exam of the semester and feeling like it's time to get back to TOBL, however briefly. I still don't have a camera to record test footage but that may change soon. Until then, here is the little guy in his most primitive form a.k.a. being held together by two whole zip-ties.

Yup, two.

So far testing has been limited to some laps around the apartment, during which I have already broken yet another spline gear. Reassembling the HS-81 plastic gear servos has worked out well. One of the wheel gears was a little tight, but has since been fixed. So now the plastic gears should last longer than 10 minutes.

Since the servos were modified they don't center very well. I suspect this is because the resistors that replaced the potentiometer do not match exactly. However, I did trim them in software and even after wearing the battery down a bit the neutral point doesn't drift much. As often as I ramble about servos I've learned my lesson and my future projects will likely use motors, for drive purposes at least.

Speaking of future projects, my V1.1 XPWMShields are finally in. Somehow they were delivered twice? Go figure. I think the perfectly good V1.0 board will remain on TOBL as not to have wasted $33 and shipping. I'll be able to comment more on the functionality (namely wireless uploading!) once I get some new Nanos to test them.

On a side note, I've recently started working at the Micro Robotics Research Lab. I thought I was into making things on a small scale...not even close! This lab concentrates on MEMS, fabrication techniques, and small scale robotics in general. For example, one team is designing a similar wireless communications board to XPWMShield, except that the board is approximately 1cmx1cm! Very cool stuff. Technically I'm working there for a program I'm in, but we'll see what happens. As for TOBL I will try to acquire a camera asafp!