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spiggo89
01-09-2009, 07:36 AM
Hey guys, I am contemplating purchasing some of these motors from banebots: http://banebots.com/pc/MS-16XXX-050/MS-16574-050

Just wondering if anyone has used them before and whether they would be suitable for a humanoid biped?

Thanks :veryhappy:

lnxfergy
01-09-2009, 11:08 AM
Hey guys, I am contemplating purchasing some of these motors from banebots: http://banebots.com/pc/MS-16XXX-050/MS-16574-050

Just wondering if anyone has used them before and whether they would be suitable for a humanoid biped?

Thanks :veryhappy:

Suitable for what on a biped, if you mean motors for the joints of the biped, then NO - you need a servo not a gear motor. Building your own servos from gear motors is quite the undertaking...

-Fergs

spiggo89
01-09-2009, 05:59 PM
All I was planning on doing is attaching some OpenServo boards to them along with a potentiometer, this would give me the very high torque but with a reasonable price (Also form factor) versus stock servos.

Adrenalynn
01-09-2009, 06:03 PM
If only it were that easy - we'd all do it. ;)

What are you going to use for position sensing? The board has to get highly accurate positional input from somewhere.

"The OpenServo is a combination of hardware and software meant to replace the original PCB internal to low-cost analog RC servos "**

Not low-cost motors - low-cost SERVOS - which already have all the position sensing pots, precision gearing, etc.

welcome to the forum, btw!

** From: http://openservo.com/FrontPage (http://openservo.com/FrontPage)

sam
01-09-2009, 06:19 PM
What are you going to use for position sensing? The board has to get highly accurate positional input from somewhere.


Wouldn't the potentiometer be for that?

Adrenalynn
01-09-2009, 06:32 PM
Sure! Where's the potentiometer on this? http://banebots.com/pc/MS-16XXX-050/MS-16574-050 I only see two wires. How are you mating this potentiometer to the motor gearing? How are you relating the motor shaft position to the pot shaft position?

Again, if you could just plug a board into a $15 motor and it would magically become a high-torque servo, I suspect few of us would be spending thousands of dollars on servos.

spiggo89
01-09-2009, 07:04 PM
The place I got the idea from was this forum post: http://www.lynxmotion.net/phpbb/viewtopic.php?t=2211

I'm not sure if they ever actually built one or not but I did see a video of one working someplace. The reason I want to do it this way is because I am poor and cannot afford the best servos, but I really like robots and want to build one :(

Adrenalynn
01-09-2009, 08:13 PM
It'd probably be best to ask Jim directly. 1) the motors draw a lot more current than the open servo board can handle. 2) where's the coupling to drive them 3) the weight is insane 4) the size would be pretty crazy. A several foot tall robot. 5) this isn't a "this is my first robot" project. I see many experienced roboticists with more than a year and a half into the project, and no working results? (from both the thread you linked and this one at OpenServo: http://www.openservo.com/Forums/viewtopic.php?t=670&postdays=0&postorder=asc&start=45&sid=1f69d78f03c6597825b822d4710af6eb

I don't want to be discouraging, and I certainly do wish you the best with it! I hope you'll post video here proving me wrong, seriously!

Robotics tends to never be "cheap", I'm afraid. Rovers are a less expensive route. If you go this route, I can see you easily dropping a couple thousand dollars for no working robot but a lot of bad smelling magic smoke...

P.S. I see from the threads that the OpenServo boards let go of their magic smoke - just as I expected they would under that kinda load...

spiggo89
01-09-2009, 09:01 PM
Well the motors I linked above and plan to use are pretty different from the ones in the Lynxmotion thread (Unless you were talking about the ones I linked :confused:). The Banebots ones are only 35grams and have a stall current of 1.9amps which the IRF7309s usable with the Openservo can handle. Admittedly I am a complete newbie to stuff like this, but it doesn't really seem that unfeasible to be able to make servos like this at home.

Adrenalynn
01-09-2009, 09:19 PM
Like I say, I don't want to be discouraging. If you can build a more powerful servo than Hitec and do it cheaper in onsie-twosie than they can do it in 10,000 part quantity - I can't wait! Please do post video and a tutorial in the tutorials section. Without a doubt, Trossen will blog it, and then I'm certain Make and Engadget will pick it up, and fame will be yours for the pre-decided 15mins. :)

I'm sure one can build their own servos, that's not a question. I've seen it done before, even been a part of it once or twice. We wanted more power and more accuracy than we could get from hobby-grade servos, and we got it. Each servo ended-up costing us a few hundred man-hours and about $1700 in that case. Later we figured out we could have just purchased $1500 industrial-grade servos and had more power and better accuracy - but it was a fun learning project. ;)

Nammo
01-10-2009, 01:04 AM
Hey guys, I am contemplating purchasing some of these motors from banebots: http://banebots.com/pc/MS-16XXX-050/MS-16574-050

Just wondering if anyone has used them before and whether they would be suitable for a humanoid biped?

Thanks :veryhappy:

I tried to use these for a self-balancing robot. It turned out the backlash in the gearboxes made it difficult to control. I had better results with Lynxmotion gear head motors since they had less backlash, but ultimately used very torquey continuous rotation servos (AX-12s) since the backlash was near-zero.

Backlash is not a good feature for building servos. Don't get me wrong, the Banebot motors are very powerful and small and excellent for driving wheeled robots -- but that's exactly what they were intended to do. You want something more servo-like for your task.

- Nathan

Quantum
01-10-2009, 05:37 AM
Wow this was my next project. I was going to try to build custom micro servos. i did the math and I figured based on the motor/gearboxes that i could come up with servo with torque about 200oz/in in the size of a hs-55 servo(a little bit bigger). i am still going to try it but not sure if its just a waste of time.

Paul

sam
01-10-2009, 09:46 AM
It'd probably be best to ask Jim directly. 1) the motors draw a lot more current than the open servo board can handle. 2) where's the coupling to drive them 3) the weight is insane 4) the size would be pretty crazy. A several foot tall robot. 5) this isn't a "this is my first robot" project. I see many experienced roboticists with more than a year and a half into the project, and no working results? (from both the thread you linked and this one at OpenServo: http://www.openservo.com/Forums/viewtopic.php?t=670&postdays=0&postorder=asc&start=45&sid=1f69d78f03c6597825b822d4710af6eb

I don't want to be discouraging, and I certainly do wish you the best with it! I hope you'll post video here proving me wrong, seriously!

Robotics tends to never be "cheap", I'm afraid. Rovers are a less expensive route. If you go this route, I can see you easily dropping a couple thousand dollars for no working robot but a lot of bad smelling magic smoke...

P.S. I see from the threads that the OpenServo boards let go of their magic smoke - just as I expected they would under that kinda load...

1-I beleive in the thread, Jim said that he changed to antehr board for this experiment.
Weight and size : IT was planned for the torso of a Johnny 5 if I remember correctky, so heavy and big wern't to much of a problem. On humanoids thought this project would be...

Adrenalynn
01-10-2009, 02:07 PM
There's more than just Jim's thread on it. Have a look at the OpenServo threads too.

The OP isn't looking to use it to power the waist of a hibred track rover, he's looking to run a humanoid. Apples/Oranges.

sam
01-10-2009, 03:20 PM
Yes of course, I was just refering to Jim's thread and situation since spiggo linked it.

spiggo89
01-11-2009, 12:18 AM
The primary reason I was looking at Banebots is because they were the only people supplying the motors + gears for reasonable prices. The Lynxmotion ones are probably better sized, along with their better torque/rpm ratios but they are simply more expensive.

If anyone knew of any where that sold cheap motors with gears I would very much appreciate a heads up. (I'm looking at China, but my searches have turned up nothing)