PCB Linear Motors For Model Trains

May 19, 2022 by Anne Ogborn 34 Comments

Modeling a railroad is hard. Railroads are large, linear pieces of civil engineering. So many modelers are drawn to the smallest scale they can use. Recently a new scale, named T, at 1:450 has been pushing this barrier. But fitting a reliable mechanical drive mechanism and MCU board in a package this size is a challenge. In practice, even more of a problem is getting reliable electrical contact through a metal wheel on metal track (about the worst possible design for a contact).

T always seemed to us a long way out on the bleeding edge. But all that may have changed. In a recent Hackaday.io writeup, author [Martin] describes a PCB technology based linear motor system to externally drive T scale locomotives.

The system uses 4mm planar coils. The underside of the PCB has another coil, so the effective pitch is 2mm. With microstepping, a step of 0.25mm is possible, and trains run smoothly. Current is 3-400mA. Continue reading “PCB Linear Motors For Model Trains” →

Verbot Goes To The Dark Side

May 9, 2022 by Adam Fabio 14 Comments

What happens to old, neglected 1980s toy robots? According to the [Randi Rain], they turn to the dark side! Way back in the ’80s, Tomy had an entire line of robots — from keychain wind-up toys to rolling, talking machines almost 2 feet tall. Tucked into the middle of this line was Verbot. Verbot’s claim to fame is that it is a voice-controlled robot. More than that, it was speaker-dependent. Train the robot with commands like “go forward” and then watch as it responds to your every command.

As you might guess, the speech recognition wasn’t great by today’s standards. Recognition was handled by a Microcontroller — a Mitsubishi product that was possibly a mask programmed 8051 variant. Pretty novel for an 80s toy — in fact, there’s a patent for it.

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Building Reaction Wheels With Python And LEGO

April 27, 2022 by Lewin Day 3 Comments

Reaction wheels are useful things, typically used by satellites to keep themselves oriented the right way up in space. Turning the reaction wheel creates an equal and opposite torque in the spacecraft, allowing it to point and rotate itself accurately. The same technique also works here on Earth, and [Brick Experiment Channel] decided to build one out of LEGO to control an inverted pendulum.

The initial design using a small LEGO wheel on an inverted pendulum was only able to work reliably over a 4-degree angle from the vertical. Upgrading the wheel to a larger, heavier one enabled the wheel to instead work over a 28-degree range instead.

A MPU9250 inertial measurement unit was pressed into service for control of the reaction wheel, fitted to the base of the pendulum and read by a Raspberry Pi. The Pi takes accelerometer and gyroscope readings, and then controls the motor on the pendulum with a PID controller to keep the inverted pendulum upright.

The video goes into a great deal of detail on what it takes to make the pendulum run smoothly. From changes to the control coefficients to measuring the motor’s back EMF, [Brick Experiment Channel] demonstrates everything required to make the pendulum robust to outside perturbances.

The inverted pendulum is a great way to learn about control theory, as we’ve seen time and again.

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2022 Sci-Fi Contest: A Star Wars Mouse Droid Of Your Very Own

April 21, 2022 by Lewin Day 5 Comments

The show-stealing droids of Star Wars, R2-D2 and C-3PO, are quite challenging to replicate at home, due to their size and complexity. [curiousmarc] had built the former, with much work going into drawing and design. The more humble Mouse Droid, as seen skittering about the halls of the Death Star, is a considerably easier build — especially with this somewhat improvised approach.

The build relies on reject parts from [curiousmarc]’s R2-D2 build, and other stuff laying around the house, like a toy eggbeater, a VFD, and other electronic bits and pieces. An RC car chassis was placed in the droid’s vacuum-formed shell in order to provide propulsion, with much of the rest of the work being decoration of the housing with various sci-fi ephemera. There’s also a pair of Arduinos inside, controlling the VFD, sound output, and the movable antenna dish on top.

It’s a build with a lot of personality. The sounds, flickering display, and moving antenna do a lot to imbue this droid with a soul, something Lucasfilm readily achieved with many of the robots in the series. It’s something we’ve also seen in robot companion builds from [Jorvon Moss], which are quite sci-fi in their own way, too. Video after the break.

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2022 Sci-Fi Contest: The Animatronic Baby Yoda You’ve Always Wanted

April 19, 2022 by Lewin Day 2 Comments

Simple robot parts make up the internals.

When it comes to sci-fi, it’s hard to go past Star Wars, and many submissions to our contest land in that exact universe. [Kevin Harrington]’s entry is one such example, with his animatronic Baby Yoda that’s exactly as cute as you’d hope it would be.

The build is based on a Pololu Romi chassis, a simple two-wheeled differential-drive robot platform. It’s paired with a robot arm in the form of Hephaestus Arm 2, which provides the articulation for the precocious little creature. An ESP32 microcontroller serves as the brains of the operation, controlling all the servos and motors that make baby Yoda move. Control is via WiFi, using a website hosted on the ESP32 via RBE1001lib.

The animatronic baby Yoda would surely be a hit sitting on one’s shoulder at any sci-fi convention. Overall, it’s a simple robot that becomes more personable by skinning it with an adorable toy. It’s not the first baby Yoda (or Grogu) that we’ve seen, either – the popular character has inspired builds before, too! Video after the break.

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Mini DarkTower Clone Restores Your Childhood

April 15, 2022 by Kristina Panos 8 Comments

Remember DarkTower? No? Well, it’s a really cool combination board game, RPG, and computer game from 1981. Orson Welles pimped it on TV and explained it thusly: “collect three keys, lay siege to the tower, and defeat the enemy within”. The Tower itself was a battery-powered computer on lazy Susan that showed numbers on a couple of 7-segment displays, pictures via three carousels, and had a 12-button keypad. Thanks to a lawsuit, few copies remain, and even fewer of them are in working condition.

Working copies of DarkTower go for hundreds online, but who can afford such an extravagance when these 40+ year old towers are prone to battery leakage and loose connections? Certainly not [Mighty Studios], who was hoping to give the gift of DarkTower to a friend and decided to build a mini reproduction instead. Fortunately for us, the project is completely open source. You can check out the build video below, which has plenty of links, including one that goes to the code.

In this day and age, it doesn’t take much to reproduce the internals of the Tower. [Mighty Studios] pulled it off with a Feather S2, a 320 x 420 TFT LCD screen, a speaker, and a couple of momentary buttons. The screen can show all the pictures, (which were only displayed one at a time in the original game anyway), any necessary numbers, and all the requisite menu options.

[Mighty Studios] got mighty lucky when it came to the case, as [Stinkevil] had already created a dice tower version and put it on Thingiverse. After a bit of tweaking and some hole-punching, [Mighty Studios] had a mini tower scaled to the Feather S2 with just enough room to stuff in all the components and wires. Between a PDF of the original rule book and someone’s Java version of the game, [Mighty Studios] had plenty to use as a guide for programming in the rule set before mailing it off to their friend. We have to admit, we’re pretty jealous.

Don’t want to amass an army and conquer evil forces? There are all types of board games you could emulate with a microcontroller.

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Lego Fourteen-Segment Display Needs Plenty Of Motors

April 12, 2022 by Lewin Day 1 Comment

Hackers love 7-segment displays, and will gladly wax lyrical about the silly words you can almost spell on them and so on. Less appreciated are their bigger cousins, the fourteen and sixteen segment displays, which get all alphanumeric about things and are thus much easier for humans to read. You can even build the former out of Lego, as [ord] demonstrates.

A look at the mechanism driving the display.

The “segments” are made up of Lego shafts that are pushed up through a yellow matrix of holes when they are switched “on.” A full seven motors are used to make the single-character display work, each one driving two segments. Two Lego Powered Up controller bricks are required to drive everything going on here, making the final design not just mechanically complicated, but electronically complicated as well.

Amusingly, those don’t come cheap, either; the parts total cost of this build is likely somewhere between $50-100 US. You probably don’t want to build an entire scrolling message board using this design, even if it does look resplendent in black and taxi yellow.

We’ve seen [ord]’s work before, too, in the form of these mechanically magnificent 7-segment Lego displays. Video after the break.

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