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Parallax's 12V Modular Wheel and Motor Mounts - Feedback Requested!

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  • Ken GraceyKen Gracey Posts: 7,365
    edited 2007-07-30 22:56
    Wade -

    I wish everybody were as anxious as you! We welcome the requests.

    The only time that delivery dates stung us badly was in 1995 when Chip promised a BASIC Stamp 2 module and it was a year late. Our sales people had some kind of mutiny at Parallax, and who could blame them.

    Back to the question. How about by the end of August? I think we can make that date without a problem. The only issue we're dealing with is the manufacturing time of the wheels. They're just too expensive to make in their present design, but that's the way it'll be until we get a grip on the product's volume. What's nice about CNC machining is that tooling costs can be non-existent or very low, and it can give us the opportunity to assess the potential for higher volume through short-run productions. Only then will we know if we should make a cast mold with post-machining or to continue to machine them on our CNC as you see in these pictures.

    I think we'll be ready at the end of August. We're making these products entirely in our Rocklin, CA manufacturing center and there is nothing holding us back. Even if I have to load the parts on my own and talk Chip into doing the same these will be available.

    Ken Gracey

    Post Edited (Ken Gracey (Parallax)) : 7/30/2007 11:31:48 PM GMT
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-07-30 23:03
    The robot could run off a single battery. I didn’t want to make it sound difficult. It’s not really when you have the voltage overhead. At 12V you certainly do. But it also depends on what other sensors and circuits will be running as well. I plans on GPS and several PING))), etc. The base about 14” square. Take care.

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    Chris Savage
    Parallax Tech Support
  • WhitWhit Posts: 4,191
    edited 2007-08-02 02:52
    How's that big BOE Bot going?

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-02 04:34
    Whit,

    I haven’t forgotten everyone…Tomorrow I will finish mounting parts on it and take some pictures. Today all I managed to get done was to get the one caster replaced.· On another note I realized I didn't answer your question about the square tubing...It is 1" square.· Take care.

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    Chris Savage
    Parallax Tech Support
  • WhitWhit Posts: 4,191
    edited 2007-08-02 15:05
    Chris Savage (Parallax) said...
    Whit,

    I haven’t forgotten everyone…Tomorrow I will finish mounting parts on it and take some pictures. Today all I managed to get done was to get the one caster replaced.· On another note I realized I didn't answer your question about the square tubing...It is 1" square.· Take care.

    Thanks Chris,

    As much as I try to work on something robotic everyday, sometimes the best I can do is quick check here and one little project (like your caster replacement). Can't wait to see how it's going.

    Thanks also for the note on the tubing size. Looked like there were some spacers between the motors and the frames. I assume this was just to match the casters height to the wheels as far as the space between the rolling surface and frame.

    On another thread, we were discussing omni directiona wheels, I saw this http://www.acroname.com/robotics/info/ideas/omnicaster/omnicaster.html·on using these wheels as casters. Have you ever seen or tried this solution? I wonder if it would work as well as what you are doing. Looks kinda cool though! I think the best caster (tail wheel)·of all times must be the one attached in the picture below. I would really like this platform with these new motors! What a beauty...

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 8/3/2007 7:45:02 PM GMT
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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-04 00:18
    Okay,

    I didn’t get as much done as I hoped today, however I did get the top plate drilled out and the HB-25 Motor Controllers mounted underneath. The second pictures shows how things will look on top once I get them mounted. Of course I still need to mount the PING))) and IR sensors. Comments welcome. Enjoy!

    P.S. – How many of you would be interested in building something like this if we made the wheel kits and motors available as Ken originally posted? I could post the Bill of Materials for building a chassis like this and you could build it in a weekend. The chassis is very easy to assemble and cheap (~$25.00) without the top plate.

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    Chris Savage
    Parallax Engineering


    Post Edited (Chris Savage (Parallax)) : 10/24/2008 5:44:49 PM GMT
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  • TigerTiger Posts: 105
    edited 2007-08-04 02:58
    After reading through this thread, I'm not sure if everyone really understands what the shaft/mounting configuration is now for the wheels. It's really pretty easy to adapt to and it handles the high torque of the motors very well. Take a look at these close up pics and I think you will agree. ...Tiger jumpin.gif
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  • Capt. QuirkCapt. Quirk Posts: 872
    edited 2007-08-04 03:42
    A little bit late for input like mine I think, But.

    My own bussiness experience has taught me that products like this are, a real small market. Your looking at someone that has bought or made at least 2 or 3 lesser expensive, similar products·and is finally ready to pay more, for better quality.
  • ZootZoot Posts: 2,227
    edited 2007-08-04 17:11
    If you are still talking about two-pack of motors/mounts/wheels for $199, then count me in.

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    When the going gets weird, the weird turn pro. -- HST
  • Wade SmithWade Smith Posts: 25
    edited 2007-08-04 17:50
    I am almost in. What about a package deal with two HB-25 motor controllers? Or one motor/wheel/mount/HB-25 for a good package price, for those who may want two, or four, or even three wheeled bots?

    Wade
  • WhitWhit Posts: 4,191
    edited 2007-08-05 12:09
    Chris,

    Looking good...

    I would probably buy my components a bit at a time. My budget is usually about $100 - $200 at a time. At Christmas or on my birthday, it might be more. I would still love the bill of material to be posted. I have everything but the battery/charger, HB-25s and of course, the wheel, motor combo. I have one Ping and a few other sensors. I try to pick stuff up a bit a time and have been wanting some HB-25s for some other projects.

    I would prefer a package deal so my other parts could stay busy on other projects - but I would most likely move parts from project to project.

    Thanks for asking.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Wade SmithWade Smith Posts: 25
    edited 2007-08-05 20:32
    Chris,

    What made you switch from the tail-dragger to center mounted drive wheels with casters at both ends? Just curious.
  • WhitWhit Posts: 4,191
    edited 2007-08-05 21:27
    Wade,

    I think they were going for a small turning radius.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-06 01:17
    Whit is correct…A tail-dragger has to account for the rear swing. On a BOE-Bot that isn’t such a big deal…On this robot it is a bit more to worry about. Truth be told, the wooden tail-dragger version was built only to test the wheels…We beat them up pretty bad to see how they would fare. The robot was constantly run into things, off curbs, etc.

    The newer platform was built to navigate our building. It will soon be roaming through the office among the cubicles of Parallaxians so it needs to be able to turn in place without hitting something. I posted the first to pictures of this new chassis…The next ones are attached below.

    03) This is a top view of the chassis before mounting the plastic cover on top. Notice that the motor leads have not been cut. You never know when you may need the extra wire. The power cable is also shown coming in and connecting both HB-25’s.

    04) This is the underside of the robot. Only one thing was added after this photo which was the power switch for the motors. Whit, you asked about a single power source for both the BOE and the Wheels…I decided to do that on this unit because the Vin is so much higher that when the BASIC Stamp uses the chances of a brown-out are slim. Had the batteries been 7.2V I would have gone with separate power sources.

    05) This is just a close-up of the caster and HB-25 Motor Controllers.

    06) This is the top of the robot. As of this picture everything is mounted on the top except the sensors. There will be two PING))) sensors, 4 IR pairs, etc. I may add a compass or GPS, but right now we just want roaming. The power bus is setup similar to what I normally use except that I bridged the motor block to the main block via a toggle switch. This switch is rated the same as the HB-25 (25A).

    07) This picture is for scale…I know it’s hard to tell how big this robot is so I put it next to a BOE-Bot. It is pretty clear who’s the bigger dog now. For speed check the link to the video. Bear in mind since there are no sensors yet I simply programmed it to go forward (using ramping), reverse and do some spins. I will get more video after the sensors have been added. On the carpeted floor of the office this should be almost completely silent. For that reason we will be putting a tall flag on it to make sure nobody trips over it.

    Enjoy the pics and video…Take care!

    http://www.youtube.com/watch?v=8hhNXOAjEOc

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    Chris Savage
    Parallax Engineering


    Post Edited (Chris Savage (Parallax)) : 10/24/2008 5:44:05 PM GMT
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  • WhitWhit Posts: 4,191
    edited 2007-08-06 02:39
    Chris,

    It looks great. Super pictures and video! I love the flag idea for indoors. I bet it will be very quiet. Can't wait to see it finished. These new wheels and motors really open up some great new possiblities. Thanks for the informative post. You must have had a busy weekend.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • Capt. QuirkCapt. Quirk Posts: 872
    edited 2007-08-06 03:49
    That pin sure isn't very profesional looking. If you take Tiger's example and cut it in half, so there is a blind hole with a copper dowel pin sticking up on only one side (instead of a roll pin). The copper dowel could be inclosed and out of sight. Also the copper dowel pin would be a "Sacrificial Lamb" and hopefully shear before the worm gear breaks.

    Bill
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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-06 03:50
    Whit,

    Yes, a busy weekend indeed, but never too busy for robotics! I will post more pictures once the sensors are installed and more video once the robot does something more than a pre-programmed sequence. Stay tuned! There’s more to come! Take care!

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    Chris Savage
    Parallax Tech Support
  • D FaustD Faust Posts: 608
    edited 2007-08-06 13:43
    Cool!· I think that the comparison picture was very helpful, especially for gauging the wheel sizes.· Just wondering, but don't the 12V motors provide a great deal me power than that bot requires.· Mabey you should add a buzzer so every once and a while it can let people know where it is.· Or, if it is smart enough, it could beep when it enters a room.·(via a sripe in the doorway?)· Just a couple thoughts.

    For the tally, I wouldn't be buying these yet, because I am still starting out, but I would definitely consider them when my robots get bigger. (in a few years?)

    edit:· How fast would you say the robot is going?· It is hard to tell from the video.

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    D Faust

    Post Edited (D Faust) : 8/6/2007 1:48:54 PM GMT
  • Ken GraceyKen Gracey Posts: 7,365
    edited 2007-08-06 14:10
    Quirkus,

    This is a prototype. For production we would use a roll pin which does not protrude beyond the diameter provided by the back of the wheel. There would be no way to catch your finger on the roll pin.

    D. Faust,

    I think we calculated just over 3 MPH, though I'm not sure what Chris has observed in practice. These motors provide a lot of power, as you noted. One benefit of the gearing is that the robot won't roll downhill on an incline, so braking isn't required.

    Ken Gracey
  • D FaustD Faust Posts: 608
    edited 2007-08-06 14:30
    Thanks Ken. One more question, what is the weight of the bot with battery at this point? (Trying to judge performance)

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-06 14:52
    Today I was planning on mounting sensors to the chassis. Once I have that done I will get a video of it moving along with someone (Josh) walking so you can get a better perspective. Maybe I’ll have the BOE-Bot move with it as well. It moves faster than the average person walks. You may have noted it is faster than when it had the Wooden Chassis. The reason is that the mixing code we use inherently limits the straight forward and straight reverse outputs not allowing full speed. Without the R/C system the BS2 is sending a 1ms or 2ms pulse and it’s much faster.

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    Chris Savage
    Parallax Tech Support
  • D FaustD Faust Posts: 608
    edited 2007-08-06 15:23
    Thanks for putting in another thing to compare to.· Can't wait for the new video.

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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-09 02:17
    The video for speed comparison is here along with handling. Since I haven’t had enough time to get the sensors installed I programmed a preset sequence for the robot to run in our adjacent offices. I chose several patterns and ran the sequence several times before video taping it. You should be able to see the robot move faster than the average walker can move. It also turns quite nicely. I hope to have the sensors mounted before the weekend and some video from the same room with obstacle avoidance in place. Enjoy!

    http://www.youtube.com/watch?v=_lFr0N8ovdo

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    Chris Savage
    Parallax Tech Support
  • WhitWhit Posts: 4,191
    edited 2007-08-09 02:23
    Chris,

    Man that thing is cool. It is quiet inside. I love it. Can't wait to see it really sensing its way around. I still like the flag idea too.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney
  • MightorMightor Posts: 338
    edited 2007-08-09 03:46
    That bot had better be very visible when moving around in the office because I doubt people will hear it coming over the office noise. It's so nice and quiet. The actual board looks so dwarfed, hehe. Really nice job, I can't wait for the obstacle avoidance vids. Will you be making it automatically home in on a charging station when its batteries are running low?

    Gr,
    Mightor

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    | What the world needs is more geniuses with humility, there are so few of us left.
    | "Wait...if that was a compliment, why is my fist of death tingling?"
    | - Alice from Dilbert
  • D FaustD Faust Posts: 608
    edited 2007-08-09 13:25
    That goes pretty fast, the indoor enviornment gives me a better bearing on speed, thanks. I too cannot wait for the sensor video. (Just for the record)

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  • WhitWhit Posts: 4,191
    edited 2007-08-09 14:03
    Chirs,

    Watched the video again! It's pretty nice to have that big space to roll around in.

    It might be cool if the warning flag could also serve a whisker sort of function by keeping the bot from running under stuff like desks and chairs. See attached sketch.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 8/9/2007 2:34:45 PM GMT
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  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2007-08-09 14:39
    Mightor,

    The charging station idea is neat. There are very few robots that do that and it would certainly be something to look into. I would probably use a beacon-based approach. You are correct that the robot is very quiet. Only the casters really make any noise once in awhile, so when we get machined units on there it will be almost impossible to hear around a cubicle wall. To that end it has been suggested in the office that we have it play a tune or speak or something. What I am thinking is detecting approach to intersections and then beeping. That seems the most likely place for an issue (someone coming around the corner). I will also be implementing the flag Whit mentioned.

    D Faust,

    It does move quite well and the next video will probably be at full speed, however I wanted to mention it won’t be moving that fast when we put it in the office area. I will choose a lower speed for it. Not by much but again, we need to avoid any chance of a catastrophe.

    Whit,

    The space used is normally full of large round tables but I had them removed temporarily for the video. I will be doing so again once I get to the sensors video. As for the flag serving as a stress sensor, it is possible. All that would need to happen is to mount a strain gauge to the mount.

    All,

    I am also considering making the robot follow someone around using a thermopile to detect body heat. There are all kinds of applications that could be implemented. Once I have rubberized casters I am thinking Robo-Magellan type programming using our GPS Module. This weekend I am going to get all the measurements for everything and post the screw sizes used, tubing measurements, etc. Take care.

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    Chris Savage
    Parallax Tech Support
  • D FaustD Faust Posts: 608
    edited 2007-08-09 15:00
    Whit, that is a great design!!!· I think I'll put that on my next bot.smilewinkgrin.gif· My boe-bot had a problem bumping into things just above IR heightsad.gif· Chris, you·mentioned a strain sensor, why not use Whit's idea, did you not see it?· Also,·Chris, I can understand why that shouldn't move at·full speed around the office.· Parallaxians might look like this:freaked.gif· Anyway, thanks for the update.

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  • WhitWhit Posts: 4,191
    edited 2007-08-09 15:20
    All of this sounds great.

    What kind of attachment is used at a roll up charging station? I know that people do this, I've just never seen the kind of connections they make between the bot and the charging station. Seems like a reliable connection could be tricky.

    My flag sketch was just a simple switch. I will do some research on a strain gauge - I guess I knew there was such a thing, but I've never seen one used.

    As far a slowing down a bit, I was thinking the same thing. I know that there aren't many places in my house I could get going that fast. But the speed would definately be nice in a Robo-Magellan contest! The warning tune or sound with the flag is neat to. Too bad there isn't a Parallax jingle. You don't want to sound like a dump truck backing up. wink.gif I love the body heat sensor idea for following someone around. This could also be a good autostop sensor for avoiding running into someone too.

    Can't wait to see all the "documentation." As always, just the process of watching the developement is useful to me. It helps me remember that more complex designs grow that way overtime. You don't have to solve every problem at once.

    Hope you have a busy weekend.

    Edit - O.K. got it! Great article on Strain gauges on wiki here - http://en.wikipedia.org/wiki/Strain_gauge
    and piezoresistor link! Thanks Chris.

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    Whit+


    "We keep moving forward, opening new doors, and doing new things, because we're curious and curiosity keeps leading us down new paths." - Walt Disney

    Post Edited (Whit) : 8/9/2007 3:35:21 PM GMT
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