When we were working on the Best of Instructables, one of my favorite projects in the book was the “How to Make an OAWR (Obstacle Avoidance Robot)” by Clement Fletcher. The bot used laser-cut plastic components that you can either cut yourself or purchase through Ponoko. The instructions for the robot were so extraordinarily well done and the bot looked really well-design. The downloadable PDF documentation was gorgeous and looked crystal clear. All of it made me itch to actually undertake the project. So, when I discovered that Clement and his pals had created a company, called Oomlout, to promote their Arduino-based open source robot designs, and to sell kits, I jumped at the chance to review one.
The SERB, short for Arduino Controlled Servo Robot (ah… sort of), is a two-servo, three-wheeled robot development platform. Like the OAWR, it is built almost entirely of clear plastic laser-cut parts. For control, it uses the Arduino Duemilanove. There are two power sources, the logic powered by a 9V, and the motors via a 4-AA battery pack. The SERB carries a small breadboard on its back which handles the connections between all of the electronic components (re.g. the PWM lines to the motors and the Gnd line from the motor’s battery pack). Obviously, the fun starts when you use the breadboard to attach additional sensor systems and begin expanding the bot’s capabilities.
The SERB is a very handsome kit. It comes in a generic white clamshell box with a sheet of artwork glued to the lid. You can tell it’s a “mom and pop” kit operation, but that makes it all the more charming, and impressive, when you see how well it’s all done.
Inside are two sheets of 3mm (.118″) acrylic plastic with all of the components laser-cut from them. The sheets have a backing to hold all of the parts in place. All of the other components are inside small manila envelopes, clearly labeled. There’s an Assembly Guide booklet and a Wiring Diagram sheet included. Everything feels well thought-out and meticulously assembled. “Labor of love” is invisibly stamped all over everything.
Construction of the SERB was one of the most enjoyable builds I’ve done in a while. It’s a lot like putting together a Mechano or Erector Set. When you peel off the laser sheet backing, all of the parts are released from the carrier sheet. There is some clever engineering here, such as the 4.5″ ID O-rings used as tires. Two circles of acrylic are held apart by spacers at just enough width so that the O-ring tire fits snugly between them, creating a wheel. There are two of these, powered by Parallax servos, pre-hacked to provide continuous rotation. The sidewalls of the bot are held in place via slots in the base that accept nuts into which screws tie in from the side panels (think: cheap Ikea furniture fastening tech). Additional slots like this for future add-ons, along with plenty of other mounting holes, dot the plastic chassis pieces. The third, front wheel, is a caster made from a skate bearing caster.
It took under two hours to put the SERB together. All of the components are marked with parts numbers that are indicated on in the Assembly Guide. All you need to put it together is a pair of needlenose pliers and a Phillips head screwdriver. The only hiccup for me in the assembly was, when I peeled off the laser sheet backing, I didn’t realized that the “doughnut holes” inside some of the components were actual parts (these are not numbered/marked). I threw them away, only to realize they’re washers for the drive wheels and caster assembly stand-off. I retrieved them (lucky it wasn’t trash night!) and it was all good. Also getting the nuts in place, in their little slots and holding them there while you tie in the screws was aggravating in a few hard to reach places. But if the build had been entirely mindless, it wouldn’t feel like much of an accomplishment.
Once the robot is built and the batteries are in, you’re ready to roll. I honestly hate it when I build a kit like this and then have to write a program before my bot can do anything. Not here. SERB comes with a simple driving program pre-loaded onto it. Obviously, there is no sensing yet, so to control the driving, you’ll want to put some bump switches or other obstacle avoidance sensing on there ASAP. Getting programs into the SERB is done via the USB connector on the Duemilanove.
Some might think that $175 is a lot to spend on a robot kit like this. If it is for you, Oomlout offers a number of cheaper DIY options. You can build the bot entirely yourself, using the templates on the Instructable for the project, or you can buy just the hardware for $80, if you already have an Arduino and plan to cut the chassis yourself. You can even get a parts bundle sans microcontroller and servos for $50. The guys at Oomlout don’t care how you come to build their cool robots, they just want you to build their cool robots! And after my build experience, so do I!
Oomlout has posted a number of Instructables on adding various capabilities to your SERB:
They’ve also put up some images of future add-ons they’re working on: