[HH] Robotic arms controllable from Linux

[Federico Lucifredi]

Hello greg,
  I am looking at Toby Baumgarten's Trobot 4.0 — but that does not change the economics, the servo package fits right down the cost estimates you have made.

  http://www.tbaumg.com/

Best -F


On Nov 2, 2012, at 5:23 PM, Greg London wrote:

> The only one I know of is this:
> 
> http://www.imagesco.com/robotics/owi-535.html
> 
> But I assume you consider that a "toy".
> 
> The problem is:
> 
> Motors aren't cheap.
> Power FETs aren't cheap.
> heat sinks aren't cheap.
> 
> I've been working on making a "generic" motor controller and it's *hard*
> because motors that aren't "toy" motors end up taking a lot of current,
> which translates into really hefty FETs, and a lot of voltage, and that
> translates into a lot of power, which then requires really big heatsinks,
> all of which is expensive.
> 
> Once you start getting into "not-a-toy" robot arms, you're probably
> looking at several hundred dollars at a minimum, at which point, if you're
> spending that much money, you probably want to pay for the specs you want,
> and don't want to pay for specs you don't want.
> 
> Trying to get 1 horsepower out of a low voltage DC motor that you can
> switch on and off rapidly via PWM ends up being a pain. Motor voltages for
> higher powers quickly jump from 12v to 24v to 48v and even 96v. Several
> voltage jumps push you into more expensive FETs because they all have
> different max voltages they can handle.
> 
> I think I came up with a design that has basically two possible FETs, one
> for 48 and below, the other for over 48v, handling currents somewhere up
> to 80 to 100 amps or so. Even with low Vds fets, it still ended up needing
> some serious heatsinking if you want the motors on all the time.
> heatsinks, it turns out, can be more expensive then the cost of all the
> electronic components combined.
> 
> It all got rather depressing, and I put the design on the shelf (or,
> technically, on my harddrive) and left it there. When I've feeling more
> motivation, I might dust it off and give it another go.
> 
> Here's an off the shelf controller that handles up to 24v at 40amps motors
> for $90. You'll need three or four for a robot arm. So, you're already
> looking at $300 and up.
> 
> The short of it is that they make "toy" robots because "not-a-toy" robots
> are really, really, expensive.
> 
> Greg
> 
> 
> 
>> I'm looking for a robotic arm that can be controlled via Linux or
>> Arduino. Cheap but not a tow. There is one out there that litters my
>> google results but it is not really usable as anything but a toy. It
>> costs about $50 and sold under a few different names.
>> 
>> Anyone have know of any?
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> 
> 
> -- 
> 
> 
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_________________________________________
-- "'Problem' is a bleak word for challenge" - Richard Fish
(Federico L. Lucifredi) - flucifredi at acm.org - GnuPG 0x4A73884C