Let's Make Robots!

Octabot II


Here is my first attempt at building a hobby robot.  I'm using an Octobot II platform from Budget Robotics.  The MCU is a PICAXE 090 experimentor's board with a PICAXE 28X1 chip.

The Octabot II platform uses 2 R/C servos that have been modified for continuous rotation.

There is a Parrallax Ping))) ultrasonic sensor mounted on the turret.  The turret has 180 degrees of movement via an unmodified R/C servo.

I've installed an IR receiver so that I can operate it by remote control, or let it operate autonomously.

I'm at the point now where I have all of the hardware operational, and am in the process of debugging my code.

Thank you everyone at LMR for the inspiration and advice.

Duane S

Wilson, NC  USA

 

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Thanks for the WD40 advice.  I'm very familiar with WD40.  Tried it in fact, with little or no improvement.  It's just a small, cheap caster, with no swivel bearing.  :(

I may try helping it out with a little lapping compound when I get a chance.  I'm hoping that changing from D cells to AA cells wil help in the meantime.

Duane S

Wilson, NC  USA

A free running omniwheel makes a very good castor. Just put it on a fixed axle so it can turn and the rollers around its perimeter take care of the sideways motion.

Thanks asmith,  for the suggestion. 

I've thought about that, but haven't tried it yet.

I have a 40 mm double row omni-wheel that would "just" barely fit.   I'll have to fab up a bracket of some kind first, but that's do-able.

I do not doubt that it would work very well on a hard surface, but I do wonder about how it'd work on carpet.  Heck, the castor works fine on a hard surface, but 95% of my home is carpeted. 

Hmmm.... I guess that it would never be "sideways" to the carpet during forward travel, so it shouldn't "steer" the 'bot wrong, but I wonder how it'd work when I WANT the 'bot to spin around.  (like in a Zero Turn Radius move).

Have you ever tried using an omniwheel as a castor on carpet?

Duane S

Wilson, NC  USA

I haven't used an omniwheel as a castor myself, but I've seen photos and videos of small robots where it is done. You should be able to verify very easily for yourself if it will work on your carpet by putting your omniwheels on a suitable axle and holding them there while you drag them sideways across your carpet. That way you'll be able to tell if they will still move freely or not. I have the same kind of omniwheels as you I believe and mine work fine on my carpet.
May I ask where you got the omni wheels?
Wow.. no glue, no solder? :D Video?

No, there is no glue involved (yet), but there was plenty of soldering.

The PICAXE 090 experimentor's board came as a bare PCB and a bag of parts.  :)

I did video it's first attempt at autonomous operation which was not sucessful due to a code glitch.  It was doing things that I had not intended :(

It's a "MOV" file, so many people would not be able to view it.

Duane S

Videos are to be uploaded on Youtube or google or similar, and then embedded in here. Edit your project and see the options for more. Comon, we wanna see ;)

I've never uploaded anything to Youtube, and do not even have an account.  I'll get there before long, but for now I'm concentrating on making the bot work.  I have limited "hobby time", and I'd like my first video to be something that I'm happy to bring to "show and tell".  :)  After that, I'll show the failed first attempt.  :)  I promise. 

I've learned at lot in this effort.  One mistake that I made was to use 4 D cell batteries for my servo power.  (I was trying to save myself from constantly changing batteries).  Even though they are mounted "almost centered" over the axles, the weight on the rear caster seems to be too much for it to move freely.  As a result, it's impossible to move in anything close to a straight line on carpet.  (It works O.K. on tile though.)  I guess I'll go with 4 AA's instead.

Duane S