Flutterby™! : Circuits, model railroads and snakes

Next unread comment / Catchup all unread comments User Account Info | Logout | XML/Pilot/etc versions | Long version (with comments) | Weblog archives | Site Map | | Browse Topics

Circuits, model railroads and snakes

2003-12-10 04:07:08.346058+00 by Dan Lyke 9 comments

Flush with my microcontroller successes and barely coherent due to my lack of sleep from the trip to deploy it, I've been searching for a few things. Looking for information on current sensing lead me to Rob Paisley's model railroad electronics pages, specifically his various transistor throttle circuits go step-by-step through the sequence so I can understand the whys and wherefores of each component. But in my searching I've also learned that knowing a lot of this is like knowing assembly language, especially since I'm planning on driving everything from a microcontroller and software anyway: it seems perfectly reasonable to just get something like a LMD18200 3 amp H-bridge motor driver with internal overload protection and a current draw output and not worry about designing my own circuit breakers.

Relatedly, I'm looking for a good practical intro to electromagnetic actuators. I've been thinking about ways to build a cheap robot that goes beyond just repurposing an RC car chassis or similar. The big problem is that as you add axiis of motion, prices go up. Yes, I could build yet another hexapod that shuffles like a tank, but why? And doing a hexapod right takes 16 motors or more. I could do a two legged walker that shuffles in 3 or 4 axiis, but the 11 or 12 (3 ankle, knee, two hip, times two) to do it right starts to cost a lot.

What about a snake? Drop a small wheel on each segment, drive the joints between each segment with two electromagnets and a fixed magnet. Driver circuits become easy, especially if the stall currents on the actuators is low. If it's long enough I'd bet it'd be pretty good at some terrain that'd give anything else of equivalent articulation a lot of trouble. Scales nicely, could be built small or large. Probably not something I'll get to soon, but worth just letting a few background neurons play with the idea a bit more.

[ related topics: Robotics Machinery Embedded Devices Trains Toys ]

comments in ascending chronological order (reverse):

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 12:47:23.329047+00 by: meuon

Back in '93ish, you showed me Muscle Wire aka Nitinol and Flexinol. I went looking for advanced projects using it, but found none. Apparently bundling it (into larger 'muscle bundles') does not work, heat buildup and thermal mass causes it to be very slow to relax again. I'd always wondered why pneumatics were not used more. The things you can do with both pressure and vacuum, or pressure from either side of a piston is pretty efficient.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 16:39:40.469682+00 by: td

You know about Gavin Miller's snakes, right?

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 16:58:39.5397+00 by: Dan Lyke

Hmmmm... The reason I hadn't thought about pneumatics for this is that in terms of drivers, they require some other mechanical actuator as well, so they're really only good for larger systems that you can't just move with the initial actuator. There's also no reason to limit yourself to pistons with pneumatics, inflating hoses and bladders (and especially bladders inside of fabric shapes) can give you some great muscle replacements.

The problem with vaccuum is, of course, that pesky 14.7 PSI issue.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 17:00:45.665734+00 by: Dan Lyke

Thanks, Tom, I had vague recollections that someone had played with this before, but for what seems to be such a totally practical form factor I haven't seen any at local shindigs I've been to.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 17:22:18.374421+00 by: Dan Lyke [edit history]

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 17:23:17.871255+00 by: Dan Lyke

He also appears to be using standard servos, which works, but part of the appeal of the snake form is that I think it could work with just left to right pressure and only a few feedback sensors, not full servos all the way down the body.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-10 20:43:59.592428+00 by: Jerry Kindall

Hah. A snake robot that "scales" nicely.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-11 05:27:28.696122+00 by: Dan Lyke

Snicker. Sorry. Well kinda, I'd be sorry if it were intentional.

#Comment Re: Circuits, model railroads and snakes made: 2003-12-13 17:37:28.010709+00 by: baylink

Me, personally, I just wanna build K-9.

More accurately, I just wanna *have* K-9; if I gotta build him to get there, so be it.

But he couldn't climb stairs (and more importantly, curbs) reasonably.