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@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? >> _______________________________________________ >> Hardwarehacking mailing list >> [email protected] >> http://lists.blu.org/mailman/listinfo/hardwarehacking >> > > > -- > > > _______________________________________________ > Hardwarehacking mailing list > [email protected] > http://lists.blu.org/mailman/listinfo/hardwarehacking _________________________________________ -- "'Problem' is a bleak word for challenge" - Richard Fish (Federico L. Lucifredi) - flucifredi at acm.org - GnuPG 0x4A73884C _______________________________________________ Hardwarehacking mailing list [email protected] http://lists.blu.org/mailman/listinfo/hardwarehacking
