Touch-A-Sketch Gives an Old Toy a New Twist

After nearly 60 years and a lot of stairs and squares, there is finally an easier way to draw on an Etch A Sketch®. For their final project in embedded microcontroller class, [Serena, Francis, and Alejandro] implemented a motor-driven solution that takes input from a touch screen.

Curves are a breeze to draw with a stylus instead of joysticks, but it’s still a 2-D plotter and must be treated as such. The Touch-A-Sketch system relies on the toy’s stylus starting in the lower left hand corner, so all masterpieces must begin at (0,0) on the knobs and the touch screen.

The BOM for this project is minimal. A PIC32 collects the input coordinates from the touch screen and sends them to a pair of stepper motors attached to the toy’s knobs. Each motor is driven by a Darlington array that quickly required a homemade heat sink, so there’s even a hack within the hack. The team was unable to source couplers that could deal with the discrepancy between the motor and knob shaft sizes, so they ended up mounting the motors in a small plywood table and attaching them to the stock knobs with Velcro. This worked out for the better, since the Etch A Sketch® screen still has to be reset the old-fashioned way.

They also considered using belts to drive the knobs like this clock we saw a few years ago, but they wanted to circumvent slippage. Pour another glass of your aunt’s high-octane eggnog and watch Touch-A-Sketch draw something festive after the break.

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Balance like a Mountain Goat on this Simple Stewart Platform

No goats were harmed in the making of this 3-DOF Stewart platform for [Bruce Land]’s microcontrollers course at Cornell.

If the name “Stewart platform” doesn’t ring a bell, the video below will help you out. [Team Microgoats] built a small version of the mechanical system commonly seen in flight simulators, opting for 3 DOF  to simplify the design. Their PIC32-controlled steppers can wobble and weave the table in response to inputs from an MPU-6050 six-axis accelerometer embedded in the base of a 3D-printed goat. Said goat appears to serve no other role in the build, but goats are cool, so why not? And if you’ve ever seen a mountain goat frolicking across a sheer vertical rock face like it was walking across a parking lot, you’ll understand the connection to the balance and control offered by a Stewart platform.

[Bruce Land]’s course is always a bonanza of neat projects that pop up in our tipline this time of year, like a POV box fan, a coin cell Rickrolling throwie, and a dynamometer for small electric motors.

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An Automated Ice Cream Topper For The Ultimate In Zero Effort Desserts

It’s a highly personal facet of the eating experience, the choice of topping applied to your frozen dessert. Everybody has their own preferences when it comes to whipped cream, sprinkles, and chocolate syrup. Should the maintenance of those preferences become a chore, there is a machine for that, and it comes courtesy of [Kristen Vilcans] and [Ramita Pinsuwannakub] in the form of their Cornell University project as students of [Bruce Land]. Their Automated Ice Cream Topper holds profiles for each registered user, and dispenses whipped cream, chocolate sauce, and candy sprinkles onto ice cream at the simple push of a button.

The hardware seems simple enough until you appreciate the many iterations used to ensure that it works smoothly. The bowl of ice cream sits on a motorised turntable, and a can of whipped cream is suspended above it upon rails made from kebab skewers. A servo and lever operates the can to release the cream.  Meanwhile the sprinkles come from an inverted spice jar with a motorised disc to momentary align a hole with the jar’s spout, and the chocolate syrup comes courtesy of an air pump and some plastic tubing. The whole is controlled from a PIC32 microcontroller.

It is refreshing to see that such projects do not have to tackle especially high-tech problems to be extremely successful. We could all dispense our own toppings, but now we know there’s s machine for the task, who wouldn’t want to give it a try!

If ice cream student projects are your thing, perhaps you’d like a 3D printer?

POV Display is FAN-tastic

Persistence-of-vision displays come in all shapes and sizes. But when you get a couple of [Bruce Land’s] students involved, well let’s just say they tend to up the ante. When [Emily] and [Han] decided to make a POV display for their next class project, they did so with style. Unsatisfied with smaller displays they saw on YouTube – they decided to make a larger one out of an old box fan and a DotStar LED strip, which are similar to NeoPixels except they use SPI, which means you can update the LEDs at a much faster rate. This makes them perfect for a POV display!

As usual with projects out of Cornell’s EE class – this POV project is extremely well documented and it’s nice to see the fundamental details of a POV display explained. So be sure to check out this project if you’re rusty on the inner workings of POV displays.

We’ve seen some interesting POV displays here at Hackaday, including one strapped to a dog to display its running speed. What’s the coolest POV display you’ve seen?

A Robot Arm for Virtual Beer Pong

Leave it to engineering students to redefine partying. [Hyun], [Justin], and [Daniel] have done exactly that for their final project by building a virtually-controlled robotic arm that plays beer pong.

There are two main parts to this build: a sleeve worn by the user, and the robotic arm itself. The sleeve has IMUs at the elbow and wrist and a PIC32 that calculates their respective angles. The sleeve sends angle data to a second PIC32 where it is translated it into PWM signals and sent to the arm.

There’s a pressure sensor wired sleeve-side that’s worn between forefinger and thumb and functions as a release mechanism. You don’t actually have to fling your forearm forward to get the robot to throw, but you can if you want to. The arm itself is built from three micro servos and mounted for stability. The spoon was a compromise. They tried for a while to mimic fingers, but didn’t have enough time to implement grasping and releasing on top of everything else.

Initially, the team wanted wireless communication between the sleeve and the arm. They got it to work with a pair of XBees, but found that RF was only good for short periods of use. Communication is much smoother over UART, which you can see in the video below.

You don’t have to have a machine shop or even a 3-D printer to build a robot arm. Here’s another bot made from scrap wood whose sole purpose is to dunk tea bags.

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Guitar Game Plays with Enhanced Realism

There’s a lot more to learning how to play the guitar than just playing the right notes at the right time and in the right order. To produce any sound at all requires learning how to do completely different things with your hands simultaneously, unless maybe you’re a direct descendant of Eddie Van Halen and thus born to do hammer ons. There’s a bunch of other stuff that comes with the territory, like stringing the thing, tuning it, and storing it properly, all of which can be frustrating and discouraging to new players. Add in the calluses, and it’s no wonder people like Guitar Hero so much.

[Jake] and [Jonah] have found a way to bridge the gap between pushing candy colored buttons and developing fireproof calluses and enough grip strength to crush a tin can. For their final project in [Bruce Land]’s embedded microcontroller design class, they made a guitar video game and a controller that’s much closer to the experience of actually playing a guitar. Whether you’re learning to play for real or just want to have fun, the game is a good introduction to the coordination required to make more than just noise.

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Smart Station Runs Entertainment, Is Entertainment

It’s that special time of year—time for the parade of student projects from [Bruce Land]’s embedded microcontroller design course at Cornell. [Timothy], [Dhruv], and [Shaurya] are all into remote sensing and control applications, so they built a smart station that combines audiovisual entertainment with environmental sensing.

As with the other projects in this course, the smart station is built on a PIC32 dev board. It does Bluetooth audio playback via RN-52 module and has a beat-matching light show in the form of a NeoPixel ring mounted atop the 3D-printed enclosure. But those blinkenlights aren’t just there to party. They also provide visual feedback about the environment, which comes from user-adjustable high and low trigger values for the mic, an accelerometer, a temperature and humidity sensor, and a luminosity sensor.

The group wanted to add an ultrasonic wake-up feature, but it refused to work with the 3.3V from the PIC. The NeoPixel ring wanted 5V too, but isn’t as picky. It looks to be plenty bright at 3.3V. Another challenge came from combining I²C, UART, analog inputs, and digital outputs. They had to go to the chip’s errata to verify it, but it’s there: whenever I²C1 is enabled, the first two analog pins are compromised, and there’s no official solution. The team got around it by using a single analog pin and a multiplexer. You can check out those blinkenlights after the break.

Maybe you prefer working in wood. If so, you might like this hexagonal take on audio-visualization.

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