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Nice $10 Gearmotor — Parallax Forums

Nice $10 Gearmotor

ercoerco Posts: 20,255
edited 2012-11-26 13:20 in Robotics
I'm starting a new diff-drive robot platform in the 15-pound category.·This will be my biggest autonomous bot yet.·I'm using·two·surplus gearmotors & wheels, and I've tracked·extras down online for ~$10 each at http://www.mpja.com/prodinfo.asp?number=17971+MD·and http://www.allelectronics.com/make-a-store/item/DCM-351/24-VDC-GEAR-MOTOR-W/-TURNTABLE/1.html·. My wheel is slightly different, but the motor·number & specs match, so I'm ordering more.

These are unusually nice·24V gearmotors in a sealed metal case with bushings and spur gears w/minimum backlash. Excellent efficiency, no worm drives here. Motor is a small China-made RS-380SH. Operates nicely at 12V, which is what I plan to use, a big·cheap gel cell.· Stall current is only half an amp at 12V! No-load speed on the wheel provided is a stately ~8 inches/second, ~ 22 RPM. A bargain at $10.

My long range goal is a·large boe-bot/scribbler type BS-2 platform with collision avoidance using encoders and such from·the·Scribbler encoder project.



17971.jpg


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·"If you build it, they will come."

Post Edited (erco) : 11/10/2009 5:24:19 PM GMT
«1

Comments

  • WhitWhit Posts: 4,191
    edited 2009-11-03 20:43
    erco said...

    My long range goal is a·large boe-bot/scribbler type BS-2 platform with collision avoidance for·transporting ba...,·er, cargo from room to room, using encoders and such from·the·Scribbler encoder project to enable supervised navigation. It's very precious cargo I'm hauling. smile.gif

    I think sleep deprivation is beginning to set in. smilewinkgrin.gif· I really like the motors. Great price!

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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
  • SRLMSRLM Posts: 5,045
    edited 2009-11-06 00:00
    I saw one of these in action today. The guy in the lab was running it at 40v, and it didn't even get hot...
  • ercoerco Posts: 20,255
    edited 2009-11-06 11:56
    The only problem so far with these drive units are the tires. They are an O-ring in a shallow groove, and they are not a super tight fit. The product descriptions list this as a "friction drive" to move something else, as opposed to being a ground-based rolling tire. When I did a one-motor turn, the O-ring on the stationary tire came off, since it was rotating/scrubbing in place. It stayed on fine for a two-motor turn in place. I can live with that, but I suspect that the O-ring will slip on the wheel somewhat in normal use, which will kill odometry efforts. Can't really glue the thin O-ring to the nylon wheel, so I may have to come up with different tires.

    Nov 13 edit: I did find a smaller OD O-ring that fits much tighter, it stays in place perfectly for one-motor turns.

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    ·"If you build it, they will come."

    Post Edited (erco) : 11/14/2009 4:12:27 AM GMT
  • ercoerco Posts: 20,255
    edited 2009-11-15 23:05
    My encoders aren't functional yet, but the motorized platform drives very nicely! BS2 controller board is driving programmed s-turns, squares and figure 8's at 2 speeds and looks quite promising. Next I'll finish the encoders and add IR control & proximity sensors for collision avoidance.

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    ·"If you build it, they will come."
  • EverQuriousEverQurious Posts: 48
    edited 2009-12-31 17:48
    I just ordered a pair of the gearmotor you specified and am most anxious to see how they will work out for a bot I have in mind.
    I hope you keep us apprised of your projects progress and I will do the same with mine. I wanted Parrallax's nice motor / encoder but hell, for 20 bucks as opposed to 279.00 I thought I can't go too far wrong. even if it turns out to be one of those all important lessons in what just won't work. All Knowledge is good knowledge. Well god luck my friend and have a lot of FUN.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • Mike CookMike Cook Posts: 829
    edited 2009-12-31 18:27
    Sorry for the late notice.............but I think these are the same motors:

    http://www.goldmine-elec-products.com/prodinfo.asp?number=g17222

    On Sale for $6.00 each until 12/31/09!

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    Mike
  • sailman58sailman58 Posts: 162
    edited 2009-12-31 18:56
    Hi Mike,

    Better late than never! I just snagged 4. Don't know what I'll do with them, but the price was right.

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    Ron aka sailman58
  • WhitWhit Posts: 4,191
    edited 2009-12-31 22:57
    erco,

    You indicated on another thread that the precious cargo carriers were up and running. I would love to see some video!

    Hope you all had a great Christmas.

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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
  • ercoerco Posts: 20,255
    edited 2010-01-01 17:28
    Mike:

    Great find! That's quite a bargain at $6. I did order 6 more plus some other stuff yesterday. I think you guys will like the motors. Strong & ready to go, great for robotics. Their main quirk is higher voltage (up to 24V), which some small motor controllers can't handle. But the current is low, so you have many options. I'm using my simple 4-state relay H-bridge I posted here a while back with very good results. I have 2 speeds: high is 18V direct, low is 12V direct, plus I have coast and dynamic braking. Ultra-simple. I'll post a video when I can.

    Happy 2010,

    erco

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    ·"If you build it, they will come."
  • EverQuriousEverQurious Posts: 48
    edited 2010-01-04 05:40
    Try using a slightly wider and slightly smaller diameter o rings. Also you could run a small bead of silicone caulk inside the hub track and then set the standard o ring in place. In case you run into a problem the cured caulk pulls right off. No harm done and it just may solve your wheel/tire splipage problem.

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • ercoerco Posts: 20,255
    edited 2010-01-04 06:29
    Yep, smaller dia O-ring solved it. See my follow-up post at http://forums.parallax.com/showthread.php?p=869446

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    ·"If you build it, they will come."
  • ercoerco Posts: 20,255
    edited 2010-01-09 00:47
    I just opened up the gear motor·housing to have a peek inside. It took a bit of drilling since the case was staked shut, so I thought I'd share a pic of the insides and save you the trouble. It's a nice rigid die-cast case with a stamped steel cover. Inside, you see big, thick·all-metal gears that·look·durable. It is well-lubricated with lithium grease, and there are 2 beefy bronze (?) bushings on the output shaft. There is minor output shaft end-play, but really almost no backlash since the output gear is so large. I think this is a tremendous value in a motor for a robot, and I used two of them in my platform at http://forums.parallax.com/showthread.php?p=869446·. BTW, the case has four threaded·mounting holes,·so if you do drill your case open like I did, you can·use·four 10-32 screws to seal it up as good as new.





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    ·"If you build it, they will come."

    Post Edited (erco) : 1/9/2010 12:59:39 AM GMT
    gearmotorsm.jpg
    653 x 490 - 60K
  • EverQuriousEverQurious Posts: 48
    edited 2010-01-09 11:11
    Great motor, great price. Just completed the drive base layout and still using 2 Fisher Price type H batteries,providing a whopping 18 pounds the gear train performs great. Plenty of power, very smooth and quite operation running at 12 V. This could be my best BOT yet. Thanks for the heads up on these all in one motor/gearbox/wheel. Very pleased. May have to stock up on a few more for future projects

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    EverQurious

    Try not to fret and worry bout the things that you have not...
    Just remember to be thankful for the things you've got !!!
  • ercoerco Posts: 20,255
    edited 2010-01-14 07:43
    That output shaft end-play came back to bite me. I put optical wheel encoders on these wheels on my Poor Cousin robotic platform and their output signals were erratic until I made simple thrust plates and CA'ed (superglued) them on the outside of the back of each motor housing. There's an optimal gap between the sensor and the encoder disk and the gearmotor's end-play was letting the disk get to close to the sensor. Now there's no end play and the encoders are working perfectly.

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    ·"If you build it, they will come."

    Post Edited (erco) : 1/14/2010 7:52:34 AM GMT
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  • ercoerco Posts: 20,255
    edited 2010-01-19 02:20
    My stronger and less-ghetto solution to solve the end-play problem. A·fabricated piece of sheet aluminum retained in an unused tapped hole.




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  • Martin_HMartin_H Posts: 4,051
    edited 2010-03-06 14:58
    Erco, the filter capacitors you have soldered on look beefier then the typical disc capacitors used for small robots. What are their specs and source?

    Moving closer to buying a pair of these motors,
    Martin
  • ercoerco Posts: 20,255
    edited 2010-03-06 16:28
    Just some big green mylar caps I had laying around. No specific reason I used these: either because they were on top in the cap drawer, or the only 6 matching units I had. Still 0.1 uF, but with an unneccessarily higher voltage rating. Three smaller 0.1 uF ceramic disk caps per motor would work as well. Most anything marked 104!

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    ·"If you build it, they will come."
  • ercoerco Posts: 20,255
    edited 2010-03-09 18:34
    On sale for $7 at http://www.goldmine-elec-products.com/prodinfo.asp?number=g17222 thru 5/1.



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    ·"If you build it, they will come."
  • ercoerco Posts: 20,255
    edited 2012-11-14 22:39
    Still a great motor, on sale for $3.49 until 11/20. Stock up!

    http://www.goldmine-elec-products.com/prodinfo.asp?number=G17222

    I used these in my BS2 Retrobot: http://www.youtube.com/watch?v=PX0IhUqnwrk and http://www.youtube.com/watch?v=VzbKlwc4GWs
  • Matt GillilandMatt Gilliland Posts: 1,406
    edited 2012-11-15 08:33
    attachment.php?attachmentid=66904&stc=1&thumb=1&d=1284503673
    Totally off topic - but just can't help myself....
    IT'S NOT PLYWOOD! - erco's using real dimension lumber - now that I can support     :thumb:
    -MattG
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2012-11-15 08:39
    These motors work great for building medium sized robots. I use a pair on this robot:

    https://plus.google.com/photos/117542001281850354871/albums/5750039804734302993/5749715296555693490?banner=pwa

    Power is from a single 12V 7Ah battery. It uses a couple Propellers for the brain, SpeakJet and TTS256 for the speech.

    Robert
  • ercoerco Posts: 20,255
    edited 2012-11-15 09:42
    Matt Gilliland wrote: »
    attachment.php?attachmentid=66904&stc=1&thumb=1&d=1284503673
    Totally off topic - but just can't help myself....
    IT'S NOT PLYWOOD! - erco's using real dimension lumber - now that I can support     :thumb:
    -MattG

    You silly goose. Those are just cross braces. That clearly-visible top plate is 100% bona fide, certified, US-pride, multi-plied, laminied (?), 1/4" plywood.

    What do I win for your glaring error? A Quadrover?
  • Martin_HMartin_H Posts: 4,051
    edited 2012-11-15 11:22
    Erco, I broke down and bought two of these, along with a few other robot parts. I have no idea what I will do with them, so they'll join the ebay steppers as motors needing a project.
  • ercoerco Posts: 20,255
    edited 2012-11-15 14:03
    Four would make a nice 4WD rover... you could even ride it indoors on hard floors on 24V if you replace the wheels.

    Harbor Freight has a coupon book out now with some small pneumatic wheels/tires for ~$3. Time to grab a half dozen. 4 for a rover, 2 for a balance bot.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-15 15:48
    Im really thinking about ordering four of these for my 4wd but the rpm is pretty low :/...but im really thinking these may be a better fit than the faulhabers and they look easy to mount. Do you have a video of a moving platform so i can get a feel for the speed

    Do you have a link to those harbor frieght wheels im about to drop 30 at the rc shop for some blow up 5 inch landing wheels but these may be a better fit! the hoolow plastics im using just have no traction and my motors have so much torque sometimes my tires spin out and get caught n small thing while the wheels spin away at 240 rpm
  • ercoerco Posts: 20,255
    edited 2012-11-15 16:39
    didja see post #20?
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-15 18:40
    hmmm some how i missed that totall.. sorry i was browsing on a pc I was repairing.

    Im curious becuse right now im trying to get my bot to drive, you made an h bridge from relays, then you are using a bs2 to control the pid loop? Where does you pwm signal come from, apparently the bs2 cant generate 2 PWM signals at once from what i found out today :/. are you flipping the relays to generate a PWM. Im sorry im just trying to understand whats going on here, may help me out a bit.

    Also I went to harbor frieght http://www.harborfreight.com/catalogsearch/result?q=pneumatic+wheels thats what came up for phneumatic wheels 5.99 is the cheapest. Also all the pneumatic wheels im seeing look heavy like the kind on dollys and such, will these motors drive thos sorts of wheels??!
  • ercoerco Posts: 20,255
    edited 2012-11-15 18:51
    bad link....
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-15 20:15
    http://www.harborfreight.com/catalogsearch/result? q=pneumatic+wheels
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-11-15 20:47
    like i said if you could id really love a real quick rundown on how your driving the two motors, and how heavy you think the wheels can be. I was really surprised i got the faulhaber motors running with 15lbs at 3v, so these motors have some awesome potential especially with a boost converter
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