When you think of a robotic arm, you’re probably thinking about digital control, microcontrollers, motor drivers, and possibly a feedback loop. Anyone who was lucky enough to have an Armatron knows this isn’t the case, but you’d still be surprised at how minimal a robotic arm can be.
[viswesh713] built a servo-powered robotic arm without a microcontroller, and with some interpretations, no digital control at all. Servos are controlled by PWM signals, with a 1 ms pulse rotating the shaft one way and a 2 ms pulse rotating the shaft the other way. What’s a cheap, popular chip that can easily be configured as a timer? Yep, the venerable 555.
The robotic arm is actually configured more like a Waldo with a master slave configuration. [viswesh] built a second arm with pots at the hinges, with the resistance of the pots controlling the signal output from a 556 dual timer chip. It’s extremely clever, at least until you realize this is how very early robotic actuators were controlled. Still, an impressive display of what can be done with a simple 555. Videos below.
Continue reading “The Un-Digital Robotic Arm”
After working on the DARPA Virtual Robotics Challenge this summer, visions of a Heinlenesque robotic actuator filled [Hunter]’s head. His lab had access to something called a Cyberglove that used flexible pots in each of the fingers, but each of these gloves cost the lab $15,000 each.
With a little help from some joystick potentiometers, [Hunter] whipped up a decent approximation of a $15,000 device that measures how much a user’s fingers are bent. The pots are tied into an Arduino and read with analogRead(), while a small Python script interprets the data for whatever application [Hunter] can imagine.
There are a few drawbacks to [Hunter]’s design – it’s not wireless, unlike the $15,000 version, and they certainly don’t look as cool as the real thing. Then again, the DIY version only cost 0.2% as much as the real deal, so we’ll let any apparent problems slide for now.
[ifixit] has apparently grown tired of tearing apart Apple’s latest gizmos, and their latest display of un-engineering has a decidedly more federal flair. You may have heard about Yasir Afifi’s discovery of a FBI-installed tracking device on his car back in October of last year. Apparently, the feds abandoned a similar device with activist Kathy Thomas. Wired magazine managed to get their hands on it, and gave it to ifixit to take apart. There’ve even posted a video.
The hardware itself isn’t that remarkable, it’s essentially a GPS receiver designed before the turn of the century paired with a short range wireless transceiver. The whole device is powered by a set of D-sized lithium-thionyl chloride batteries which should be enough juice to run the whole setup for another few decades–long enough to outlast any reasonable expectations of privacy, with freedom and justice for all.
Robot enthusiast [Vitalijus Rodnovas] built this rig to allow a humanoid robot to mimic his own body movements in real time. [Rodonovas] refers to his man-machine interface as a “master-slave suit,” but elsewhere this is often called a waldo after a prescient 1942 [Robert Heinlein] novella. This project page is slight on details and is mostly written in his native Lithuanian, but the pictures speak volumes, and with a little help from Google Translate we can learn the essential facts: The robot itself is a commercially-available kit, the Kondo KHR-1HV from Japan. The custom-built harness uses a collection of surplus Soviet-era military potentiometers (acquired on eBay) to read the positions of his elbows and shoulders, then an ATmega8-based interface board translates these readings into motion commands sent to the robot’s onboard controller. Some additional notes and code can be found on the RoboSavvy Forum.
Does it work? Just watch. His grin as the video progresses is infectious!
Hack a Day has previously covered other Waldos, but this latest deserves style points for its lightweight simplicity.