Chess Robot’s Got the Moves

[RoboAvatar]’s Chess Robot consists of a gantry-mounted arm that picks up chess pieces and places them in their new location, as directed by the software. The game begins when the human, playing white, makes a move. When a play has been made, the human player presses a button to let the robot to take its turn. You can see it in action in the videos we’ve posted below the break.

Running the robot is an Arduino UNO with a MUX shield as well as a pair of MCP23017 I/O expander chips — a total of 93 pins available! Thanks to all those pins, the Arduino is able to listen to 64 reed switches, one for every square.

The robot detects the human’s move by listening to its reed switches and identifying when there is a change. The gantry consists of X and Y tracks made out of PVC slabs, with half-inch lead screws turned by NEMA-23s and powered by ST-6600 stepper drivers.

Unlike some chess robots that rely on pre-existing software, this one features a custom minimax chess algorithm that [RoboAvatar] coded himself. It consists of Python scripts run on a computer, which interacts with the Arduino via a serial connection. In the second video, he explains how his algorithm works. You can also download the Arduino and Python files from [RoboAvatar]’s GitHub repository.

You’d be surprised how many chess-playing robots we’ve published, like the ChessM8 robot and this voice-controlled chess robot.

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An Organ Made from Back-Driven Steppers

[Josh] wrote in to tell us about an experimental instrument he’s been working on for a couple of months. We’re glad he did, because it’s a really cool project. It’s an organ that uses the principle of back-drive—applying torque to the output shaft of a motor—to create sounds.  [Josh] is back-driving four octaves worth of stepper motors with spinning wooden disks, and this generates alternating current. At the right speeds, the resulting sinusoidal waveform falls within the range of human hearing and can be amplified for maximum musical enjoyment.

[Josh] built this organ from the ground up, including the keys which are made from oak and walnut. Each of the forty-nine stepper motors has a corresponding wooden disk. The larger the wooden disk in the stack, the higher the resulting pitch. [Josh] says that if he built it for a full 88 keys, the highest note’s disk would be sixteen feet in diameter.

This stack of disks is driven independently by a separate DC motor, and the speed determines the key it will play in. When [Josh] plays a note, that note’s lever is actuated and its stepper motor makes contact with its disk in the stack. When they meet, the motor is back-driven by the spinning disk. In other words, they work in concert to produce some cool, eerie sounds.

Here’s a somewhat similar sort of build made from lasers and fans, if you consider that both instruments create music from objects that weren’t built to do so. Watch [Josh] play his stepper organ after the break. He has several build videos on his YT channel, and we’ve also embedded the one that covers the motor, power, and electronics part of the build.

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An Etch-A-Sketch to Fetch the Time

For someone who has never used stepper motors, real-time clocks, or built anything from scratch, [Dodgey99] has done a great job of bending them to his will while building his Etch-A-Sketch clock.

He used two 5V stepper motors with ULN2003 drivers. These motors are mounted on the back and rotate the knobs via pulleys. They are kind of slow; it takes about 2 1/2 minutes to draw the time, but the point of the hack is to watch the Etch-A-Sketch. [Dodgey99] is working to replace these steppers with Nema 17 motors which are much faster. [Dodgey99] used an EasyDriver for Arduino to drive them. He’s got an Arduino chip kit in this clock to save on the BOM, but you could use a regular Arduino. He left out the 5V regulator because the EasyDriver has one.

[Dodgey99] has published three sketches for the clock: one to set up the RTC so that the correct time is displayed once the Etch-A-Sketch is finished, some code to test the hardware and sample the look of the digits, and the main code to replace the test code.

The icing on this timekeeping cake is the acrylic base and mounting he’s fashioned. During his mounting trials, he learned a valuable lesson about drilling holes into an Etch-A-Sketch. You can’t shake an Etch-A-Sketch programmatically, so he rotates it with a Nema 17. Check it out after the jump.

If you’re paying attention, you’ll realize we just saw the exact opposite of this project a few hours ago: a CNC tool (laser cutter) controlled by turning Etch-A-Sketch knobs.

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Dumpster diving nets 100 Arduino-powered motor controllers

Never one to pass up the recycle pile at work, [Scott] usually doesn’t find much. A few old hard drives, maybe a ancient laptop every once in a while, but on very rare occasions he finds something actually useful. This latest haul is a gaggle of stepper motor drivers that, with a bit of work, can be reverse engineered and turned into an Arduino.

After prying into one of the plastic-enclosed boards, [Scott] found a LED, a quartet of transistors for powering the motor, and an ATMega168 microcontroller. Interestingly, most of the pins for the 168 were already broken out on the DA15 connector on each controller. The only thing needed was to build a programmer to dump the Arduino bootloader onto these little widgets.

After much trial and error (and building a new programming interface), [Scott] now has 100 Arduinos with a single stepper motor controller built in. He’s already made a toy light cycle rotate on a small stepper (after the break) and blink a LED, but with this many widgets, we’re wondering what crazy contraption [Scott] will come up with.

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USBPIC controls just about anything

Over the last few years, [Michael] has been developing a PIC microcontroller board. He calls his project USBPIC, and with the addition of a few FET drivers, H-bridges, and LED drivers his homemade dev board can handle just about anything thrown at it.

[Michael]’s board is build around a PIC18F2455 microcontroller with both an In Circuit Serial Programming header and support for a USB port included. Instead of going for a modular format where the board can expanded through shields or expansion cards, [Michael] decided to make three different versions of the USBPIC.

The TRANS USBPIC includes eight FETs for switching off high current devices totaling 32 Amps. The MATRIX board has twice as many outputs as the TRANS board, but uses ULN2803 or UDN2982 chips for driving smallish-current devices. Finally, the HBSW board takes a TRANS board and replaces four FETs with a an L298 H-bridge chip for driving two DC motors.

For what [Michael] lost in modularity, we think he gained a very tidy microcontroller board capable of driving everything from robots to LED matrix displays.

CNC zen gardening

The Harford Hackerspace in Baltimore, Maryland just went public with the zen garden they built for the Red Bull Creation contest. It’s a CNC creation that will help ease your frustration with that DIY 3d printer that you just can’t seem to get calibrated correctly.

On the hardware side the base of the machine serves as a sandbox. Finding the correct grain size of the medium was one of the more difficult parts of the build. The stylus is driven along three axes using a gantry common in CNC builds. The pulleys and some brackets were 3d printed, with the remained of the brackets being laser cut from wood. The Bullduino commands the stylus via a stepper motor control board, and drives the LEDs via a bank of MOSFETs. Limiting switches were also included to ensure an error didn’t result in damage to the device.

After the break you can see a build montage put to one of the greatest 8-bit game soundtracks of all time. The one thing we wish they would have shown is the built-in leveling bar that is responsible for “erasing” the garden.

Update: The Harford Hackerspace members came through with a new video that shows the ‘erasing’ process. You’ll find it after the break.

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An introduction to stepper motors

If you’ve been reading Hack a Day for long enough, you know about our infatuation with stepper motors. These precious little devices put the oomph into our CNC routers, 3D printers, robots, and other miscellaneous projects. Steppers aren’t your run-of-the-mill motors, though. [Steaky] posted a great introduction to stepper motors that lets you hit the ground running building any moving project you could imagine.

Apart from identifying a stepper and figuring out if it works, [Steaky] goes over how to make these motors turn. The theory behind an H-bridge is easy enough, but theory isn’t something often presented in schematics or stepper driver datasheets.

We’ve pulled more than our fair share of steppers from flatbed scanners and old printers. There’s nothing wrong with scavenging old parts, and whether you’re making a robot band to play your kid’s birthday party, robochess, or one of the many 3D printers or CNC machines, there’s going to be a stepper motor in your future.