It’s no secret that we think flexures are pretty cool, and we’ve featured a number of projects that leverage these compliant mechanisms to great effect. But when we saw flexures used in a six-DOF positioner with micron accuracy, we just had to dig a little deeper.
We’ve all heard linear motors, like those propelling Maglev trains, described as “unrolled” versions of regular electric motors. The analogy is apt and helps to understand how a linear motor works, but it begs the question: what if we could unroll the stator in two dimensions instead of just one?
That’s the idea behind [BetaChecker’s] two-axis stepper motor, which looks like it has a lot of potential for some interesting applications. Build details are sparse, but from what we can gather from the videos and the Hackaday.io post, [BetaChecker] has created a platen of 288 hand-wound copper coils, each of which can be selectively controlled through a large number of L293 H-bridge chips and an Arduino Mega. A variety of sleds, each with neodymium magnets in the base, can be applied to the platen, and depending on how the coils are energized, the sled can move in either dimension. For vertical applications, it looks like some coils are used to hold the sled to the platen while others are used to propel it. There are RGB LEDs inside the bore of each coil, although their function beyond zazzle is unclear.
We’d love more details to gauge where this is going, but with better resolution, something like this could make a great 3D-printer bed. If one-dimensional movement is enough for you, though, check out this linear stepper motor that works on a similar principle.
Tracking satellites and the ISS is pretty easy. All you really need is an SDR dongle or a handheld transceiver, a simple homebrew antenna, and a clear view of the sky. Point the antenna at the passing satellite and you’re ready to listen, or if you’re a licensed amateur, talk. But the tedious bit is the pointing. Standing in a field or on top of a tall building waving an antenna around gets tiring, and unless you’re looking for a good arm workout, limits the size of your antenna. Which is where this two-axis antenna positioner could come in handy.
While not quite up to the job it was originally intended for — positioning a 1.2-meter dish antenna — [Manuel] did manage to create a pretty capable azimuth-elevation positioner for lightweight antennas. What’s more, he did it on the cheap — only about €150. His design seemed like it was going in the right direction, with a sturdy aluminum extrusion frame and NEMA23 steppers. But the 3D-printed parts turned out to be the Achille’s heel. At the 1:40 mark in the video below (in German with English subtitles), the hefty dish antenna is putting way too much torque on the bearings, delaminating the bearing mount. But with a slender carbon-fiber Yagi, the positioner shines. The Arduino running the motion control talks GS232, so it can get tracking data directly from the web to control the antenna in real time.
Here’s hoping [Manuel] solves some of the mechanical issues with his build. Maybe he can check out this hefty dish positioner for weather satellite tracking for inspiration.
Ham radio operators are curious beasts. They’ll go to great lengths to make that critical contact, and making sure their directional antennas are pointing the right way can be a big part of punching through. Of course there are commercial antenna rotators out there, but hams also like to build their own gear, like this Raspberry Pi-controlled 2-axis rotator.
[wilho]’s main motivation for this build seems to have been the sad state of the art in commercial 2-axis rotators, which seems firmly mired in the 90s. Eschewing the analog pot sensors on DC brushed motors that seem to dominate the COTS market, [wilho] went with steppers and stout gearboxes for the moving gear. Feedback on the axes comes from 10-bit absolute encoders, and an MPU9250 9-axis IMU makes sure he knows exactly where the antenna is pointing with respect to both compass heading and elevation. A mast-mounted Rasp Pi controls everything and talks through a REST API to custom software that can return the antenna to custom set-points or track the moon, satellites, or the ISS. It’s a very impressive bit of kit that’s sure to drive your home-owners association bonkers.
For another 2-axis antenna positioner, check out 2015 Hackaday Prize finalist SATNOGS.