Hackaday Newsletter 0x33

Theory and practice walk into a dark alley. Only one of the two walks out. [HACKADAY]( China Loves Battery Swapping EVs, But Will They Ever Make It Here? [Read Article Now»]( The Real World Strikes Back By [Elliot Williams]( My son was into "[Secret Coders]( a graphic novel series wherein a pair of kids discover and thwart a plot to take over the world by learning to program in the [LOGO computer language](. When I told him that these "turtle bots" were originally actually real physical things, he wanted one. So we built one out of some nice geared DC motors I had lying around. A turtle bot has essentially three jobs: move forward in a straight line a controlled distance, turn a given number of degrees, and raise and lower a pen. If you're already screaming "use stepper motors!" at your screen, well, you're probably right. But I had these nice Faulhaber/Micromo geared motors with encoders that were just collecting dust in the closet, so I used 'em. And because of that, the robot stumbles on two of its three goals in life -- the servo pen lifter works just fine. Perfectly matched DC motors don't exist. Of course I knew this, because I've built bots with DC motors before. But they've all had complex control mechanisms and/or feedback that made it moot. Not here. This bot needs to drive perfectly straight without any lines to guide it or more interesting navigation algorithms. We spent a good half hour driving it around in not-quite-but-almost squares, tweaking each side's PWMs, running the motors backwards for short bursts to brake the wheels, and generally trying to map degrees of rotation to milliseconds of motor drive. And you know what, my son enjoyed it. The concepts were simple enough for a second grader, and guessing the right PWM values was like a game. When we finally got it good enough, there was a small celebration. Of course I know that what it really needs is encoder feedback. I installed those encoder gearmotors on purpose after all. But dealing with quadrature and probably a PID loop to control and sync the two sides is not for my son, at least not for another couple years. (They do learn closed-loop control theory in fourth grade these days, right?) I'll have to do that all offline some night while he's sleeping. But I hope he'll remember the lessons learned from stabbing at it the naive way. Abstractions are great, but no two motors are ever perfectly alike. You'd think you could just calibrate it out, but the motors differ in driven and coasting behavior, so you've got a lot more calibrating to do than you think at first. The real world is tough, and although it's important to have theory and ideas and abstractions to guide you, you're going to have to tweak to make it work when the wheels hit the floor. But also that it's fun to do so, and super rewarding when it finally draws a wonky square. From the Blog --------------------------------------------------------------- [Hair Today Gone Tomorrow: Four Men Go To Fix A Wafer Prober]( By [Dave Rowntree]( A team of engineers go to debug a broken IC fabrication facility. You'll never guess what was gumming up the works. Unless you read the article's title. [Read more »]( [Mining and Refining: Lithium, Powering the Future with Brine]( By [Dan Maloney]( Lithium makes our batteries go round! How do we get it? New techniques may waste less water. [Read more »]( [Industrial Sewing Machine: Acquired]( By [Kristina Panos]( Kristina got a sewing machine on steroids, and we get a first peek. [Read more »]( [Hackaday Podcast]( [Hackaday Podcast 155: Dual Integrating Spheres, More Magnetic Switches, PlottyBot, Red Hair in Your Wafers]( By [Hackaday Editors]( What happened last week on Hackaday? The Podcast will get you up to speed. [Read more »]( If You Missed It --------------------------------------------------------------- [Remoticon 2021 // Sergiy Nesterenko Keeps Hardware Running Through Lightning and Cosmic Rays]( [Working Model Reveals Amazing Engineering of Webb’s Mirror Actuators]( [Turning the PS4 into a Useful Linux Machine]( [3D Printed Maglev Switches Are So Hot Right Now]( [Move Aside Solar, We’re Installing An Algae Panel]( [PlottyBot: A DrawBot That Plots a Lot]( [Hackaday]( NEVER MISS A HACK [Share]( [Share]( [Share]( [Terms of Use]( [Privacy Policy]( [Hackaday.io]( [Hackaday.com]( This email was sent to {EMAIL} [why did I get this?]( [unsubscribe from this list]( [update preferences]( Hackaday.com · 61 S Fair Oaks Ave Ste 200 · Pasadena, CA 91105-2270 · USA