tbenedict is currently certified at Master level.

Name: Tom Benedict
Member since: 2006-07-28 00:51:59
Last Login: 2007-07-19 02:51:56

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Homepage: http://vix.dyndns.org/~benedict


I've been interested in robots all my life, but have only really been active in the field for the last two years. I've done systems administration, programming, astronomy, mechanical design, machining, and optics, so I'm more or less equally interested in all aspects of robotics. To date I've built (and re-built (and re-re-built)) two autonomous robots, Shallow Blue and its sister, Black Dolphin. Shallow Blue started life as a Mark III OOPic from Junun, but it now bears only passing resemblance to the original. It made its first competition appearance in December at Robofest in Hilo, Hawaii. Its second appearance will be at the UNI mail-in mini-sumo competition in April. I had hopes to run it at Robogames 2007 (with the assumption I'd lose), but airfare wasn't available. Black Dolphin is another Mark III, originally intended to be parted out for a 4WD and an R/C mini-sumo. But my wife jumped when I offered it to her. I did the mechanical and electrical mods, and she did the coding on it. And thank goodness she did! At Robofest 2006 in Hilo, Hawai'i, Black Dolphin placed first with Shallow Blue coming in right behind. Third place was taken by one of our club's younger builders, a 9-year-old who modified a Parallax mini-sumo to put in the ring. It was an outstanding event for everyone who participated, and judging from the crowd response it was exciting and fun for them, too. I hope it attracts more people to the sport of mini-sumo and robotics in general. Robofest 2007 should be a riot! My other not quite robotic project to date has been an underwater mini-ROV. I undertook the project as a way to draw people into building robots, and tried to keep the overall cost low and construction techniques simple. It made its debut at our club's second meeting, but because the buoyancy had a tendency to take on water it gradually sank during the demo. More work and testing is required before I can turn this into a build-day project for the club. Regardless, I brought my mini-ROV to Robofest as well and put it into the hands of as many kids as I could (it wasn't hard to attract them!) They had a blast driving the little pipsqueak around the ROV tank while the bigger BIRR / MATE ROVs flew around it, watching it on their video cameras. It was in use for a solid hour and a half before its batteries gave up the ghost, but by then at least fifty kids had some hands-on seat time with a small, but real ROV. I'm motivated to turn this into a classroom build-day kit so the kids building ROVs for BIRR / MATE competition can all go home with an ROV of their own, too. I've got two other robots in the works. I've abandoned work on Mule, a 4WD mini-sumo, in favor of a much more ambitious (and much more likely to fail) design called ESP. The second robot is a high speed line follower that I've finally got all the parts for. These are both still in the design and planning phase, but the line follower is pretty well advanced toward fabrication. Both of them will use Baby-Orangutan controllers from Pololu. These are AVR-based controllers, a far cry from the OOPics in Shallow Blue and Black Dolphin. The Orangutans are neat little controllers that offer a lot of cool features to newbies like me. On the subject of the Orangutans, I've been co-developing a C library for the Orangutans: http://orangutan-lib.sourceforge.net The code is fairly Orangutan-specific in some ways, but in others it's pretty generic Atmel AVR code. The LCD stuff is Orangutan-heavy, but the PWM motor control, pin change interrupt code, etc. is all generic. Speedy the line follower will use the library, as will the new mini sumo I'm working on, ESP. Several of us are working to start a local robotics club. We've been around for about a year, and the club is growing. We handed out over fifty fliers at Robofest, and with academic competitions ramping up at the local schools, we hope our membership will grow. The group's web site is http://www.cfht.hawaii.edu/~robotics . I am a home shop machinist and do mechanical design and machining at work. I've made largeish things (1.5m x 1.2m or so) down to smallish things (0.020" diameter contoured parts with 0.001" and smaller features.) I'm drawn toward smaller robots, the size of the Mark III and smaller. Gear trains for driving nano sumo bots are particularly intriguing, though I've only just started looking into this. High speed drive systems for line followers are also interesting, though plenty has already been done along these lines. (Good case in point, I abandoned all of my own home-grown solutions in favor of commercial 30:1 gear motors for Speedy.) Other areas of robotic interest include ROVs, AUVs, cave mappers, pipe-crawlers, high speed line followers, machine control (I use CNC machines in the shop), non-ortho machine control (Stewart platforms for tool motion), and remote telepresence for hostile environments. Mostly I like to have fun. It really all boils down to that. Tom


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The AVR Dragon rocks. I used it to debug an ATtiny85 with some LED blinker code running on it, and it worked like a champ. My next project is a gravity racer (or "downhiller") for a local club challenge. The idea is to take the idea of the soapbox derby (a gravity race involving a twisting curving course) and scale it down to the size of the pinewood derby. Oh, yeah, and make a robot that drives it.

So what's the appeal? No motors! No drive wheels! So the things wind up being pretty dirt cheap. If you read all the pinewood derby forums, you'd be convinced that the Secret of Speed is smooth axles, perfectly axisymmetric wheels, low drag, etc. For this? So far the Secret of Speed seems to be not hitting stuff and tuning the servo loop that handles steering. (So far none of the ones built at our club has navigated the 8' straight track without smacking wall... This isn't that easy a challenge.)

So I'm planning to use an ATtiny84, which has the 16-bit timer I need for driving the servo. (I could do a single servo on an 8-bit timer, but I've already got servo code written that uses the 16-bit timer.) The ATtiny84 can do debugWIRE, so this'll be the perfect opportunity to try the Dragon out on a for-real project. (WOOT!)

I'm looking forward to the build and to the tuning that'll happen afterward. Should be a fun robot.

The NEXT track the club's going to run is a full-blown slalom course. I'll be curious to see if the best-tuned straight-track cars perform well at all in the curves.


Dragon Steak with some Squid

I picked up an Atmel AVR Dragon + STK500 bundle from Digikey a while back to compliment my AVRISP mkII. It's an outstanding combo for the $50 I spent on it. The STK500 came pretty much ready to go, and made it worlds easier to program the stockpile of AVR chips I've built up. I'm pleased as punch with it.

The Dragon is also an impressive piece of hardware, but I didn't really get going on it until recently. It'll do debugWIRE, JTAG programming and emulation, ISP programming, HV programming, oooh, it gives me the shivers... Except it didn't come with any cables, and you basically have to wire it up differently for each device.

I ran across a neat Instructable, though, that had a nice way to make some general-purpose cables:


I've got parts ordered to build a set of these cables.

In the process of researching all this, though, I ran across some posts on http://ww.avrfreaks.net with some great names for things. One refered to the AVR Dragon + STK500 setup as a Dragon Steak. Another refered to the breakout cables for the Dragon as squid cables. So once all the bits show up next week and I get everything crimped together, I'll have a dragon steak with a side of squid. Can't beat it.

(A quick aside: If you ever need to build a cable with a lot of tiny crimp connectors, best thing you can do is get a job at a place that has a lot of crimping tools so you don't have to shell out the $500-1500 for a tool to make a $15 cable!)

Anyway, I'm looking forward to using debugWIRE for one of the projects I'm working on. It takes over the AVR chip you're using it on and clocks it one command at a time so you can step through your code on a live, running piece of hardware. I know there are simulators for the AVR, and I use them. But it's tough to fake input to a simulated ADC. With debugWIRE I won't need to. I'll be able to see what the actual ADC is seeing: my sensors. I'm stoked.


Shallow Blue lost at UNI. Not that I was entertaining any huge hopes, but I confess to feeling a little disappointed I went out that early. (Of course I lost to 2Strong2Bad, which was pretty cool to see no matter what.) Already planning for next year. But after watching the ExSpurt Mule matches, I'm pretty sure I'll lose next year, too. Bring it on!

On another note I finished my first real honest to goodness robot using the Pololu Robotics Orangutan controller. It's a line follower I've had on my bench for months called Speedy. To be honest the Orangutan is massive overkill for the project, and I was planning to use a Baby-Orangutan (which weighs a measly 3g). But my Baby-O is tied up in another project, and I had to get it finished by Monday for a club meeting.

I learned something in the process: When you're tuning a new PID loop, ALWAYS make sure your batteries are up to snuff. I did all my tuning with a 9V depleted to 6V (little did I know), so the tuning was disappointing, the speed even more so. A battery swap this morning put a smile on my face when I saw the higher speed it was getting, and made me laugh when I thought of the time I spent yesterday doing loop tuning. Anyway, it should be a fun day of tuning.


Shallow Blue is in the mail to UNI's mail-in mini-sumo competition. Yahoo! This will be Shallow Blue's first appearance off-island, so I'm excited as excited can be.

Please please please, if you are hosting a robotic competition, consider adding mail-in entries for at least some of your events. This is my first time entering an event off-island. I hope it's not my last.


Lots has happened since the 0.2 release of Orangutan-lib. I got my ThereminVision II system, and managed to barf things up before I ever got it running (adding "Don't solder chips onto boards at 5am before I get my coffee" to the list of don'ts). I'm hoping a little creative re-soldering and maybe part replacement will get the beastie up and running. Can't wait!

In other news the last of the parts for my line follower showed up. I'm re-designing the motor mounts and bot chassis to cut weight. It's already a little too over-budget on weight for my liking. If I can shave things down under 150g with battery, I'll be happy. (If I can swap batteries and get it down under 120g, I'll be a lot happier.) I'm already looking at making custom wheels for it. Trying to get those in under 5g apiece, with tire. Only time will tell.

I'm working on the software tx-only UART code for Orangutan-lib. Doesn't look like it should be too heinous, but I'd like to leave the option open for defining more than one. This will take some testing. Might be time for another release soon!

My line follower will be the first robot I build that uses Orangutan-lib, so I'm pretty stoked to see how it turns out. The next one is going to be a downhill racer, project to be announced. And once the ThereminVision II stuff is up and running, the mini-sumo that it's destined to run on will also run on Orangutan-lib. Proof's in the pudding. Hope it all works!


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