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Offline junior000Topic starter

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robotic arm
« on: August 01, 2008, 06:53:34 AM »
hi ppl,

          i am planning on building a robotic arm with four degrees of freedom(four joints).

          do you think its better to go with dc motors or servos?

          and for the body i am thinking of using wood(instead of aluminium).so is it ok to go with wood?
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www.myfirstbot.blogspot.com

Offline airman00

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Re: robotic arm
« Reply #1 on: August 01, 2008, 02:21:27 PM »
how big of an arm, what kind of payload,  we need more details!
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Offline junior000Topic starter

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Re: robotic arm
« Reply #2 on: August 01, 2008, 10:02:34 PM »
the length b'n two joints is 15 cm -20 cm(link length)

the main objective of the gripper(of the arm) is to lift an 10x10x10 cm cube weighing 50gm
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Offline Trumpkin

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Re: robotic arm
« Reply #3 on: August 03, 2008, 08:12:00 PM »
I think you should use servos.
Robots are awesome!

Offline Centaur

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Re: robotic arm
« Reply #4 on: August 04, 2008, 08:52:20 PM »
servos are way easier, both making mechanical connections and programming, and you can find some monsters with tons of torque if you really need it. 

If all else fails, you could use motors at the base and servos near the gripper where you'll need less torque.
Any intelligent fool can make things bigger, more complex, and more violent.  It takes a touch of genius - and a lot of courage - to move in the opposite direction.  ~E.F. Schumacker

Offline sonictj

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Re: robotic arm
« Reply #5 on: August 15, 2008, 12:48:00 AM »
These are the pros and con I can think of at the moment.  Steppers would also work but they are more difficult to interface.

servos:

   pros

   require no motor driver
   require only one i/o pin
   relatively inexpensive

  cons

   somewhat limited amount of rotation

DC motors

   pros
   powerful
   inexpensive
   fast

   cons
   require encoding for precision motion
   require a motor driver
   


I would recommend servos.

Offline Admin

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Re: robotic arm
« Reply #6 on: August 20, 2008, 05:46:39 PM »
Well, don't use the more expensive Hitec servos . . . they kept burning out on me on my ERP. Others reported similar problems. I'm moving to Futaba soon.

Offline Magnus

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Re: robotic arm
« Reply #7 on: August 20, 2009, 07:45:17 PM »
Goto www.ServoCity.com. They have some really powerful servos with gearboxes. Kind of expensive though.

Offline Razor Concepts

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Re: robotic arm
« Reply #8 on: August 20, 2009, 11:57:34 PM »
Don't buy servos from ServoCity, they charge crazy prices. Towerhobbies, Horizon hobby, ebay, etc.

Offline sonictj

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Re: robotic arm
« Reply #9 on: August 21, 2009, 12:09:41 AM »
Quote
Don't buy servos from ServoCity, they charge crazy prices. Towerhobbies, Horizon hobby, ebay, etc.

If you don't buy from them at least check out their product summaries.  They have more information about their products than most servo retailers.  I don't think their prices are that out of whack.  It depends on the particular item.  It always pays to shop around before any purchase regardless.
« Last Edit: August 21, 2009, 01:22:04 AM by sonictj »

Offline Trumpkin

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Re: robotic arm
« Reply #10 on: August 21, 2009, 02:12:41 PM »
read the timestamp  ;)
Robots are awesome!

Offline Admin

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Re: robotic arm
« Reply #11 on: August 21, 2009, 02:24:21 PM »
servocity has decent prices. I still shop around though, as servo prices for all the retailers fluctuate a lot.

Offline matt liao

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Re: robotic arm
« Reply #12 on: August 25, 2009, 12:03:25 AM »
I designed smart arm!

Offline gaurav.p

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Re: robotic arm
« Reply #13 on: August 25, 2009, 07:04:57 AM »
servos would be better in this and i prefer tower hobbies or dealextreme(free shipping)
nice cad image
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Offline Joker94

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Re: robotic arm
« Reply #14 on: August 25, 2009, 06:07:08 PM »
i Would go with servos for eas of use and you can get some relly high powered servos. If your are on a tight budget i would go with motors as they are inexpensive.

Offline SmAsH

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Re: robotic arm
« Reply #15 on: August 26, 2009, 12:06:30 AM »
for an arm you will most likely want servos...
just because they have position feedback, gearbox etc...
Howdy

Offline Razor Concepts

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Re: robotic arm
« Reply #16 on: August 26, 2009, 12:11:01 AM »
Servos dont have position feedback, you don't actually know where the arm is. You just hope the servo is working correctly when you tell it to go to a position  :)

Offline airman00

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Re: robotic arm
« Reply #17 on: August 26, 2009, 07:25:00 AM »
I've seen a wire being run to the servo's internal pot so you can get position feedback with a little modification.
Check out the Roboduino, Arduino-compatible board!


Link: http://curiousinventor.com/kits/roboduino

www.Narobo.com

Offline wil.hamilton

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Re: robotic arm
« Reply #18 on: August 27, 2009, 05:23:14 PM »
you can get digital servos, which i'm fairly certain have position feedback, your run of the mill servo is not a "digital" servo
use the google.  it's your friend.

 


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