Flux Capacitor Prop With Christopher Lloyd’s Stamp Of Approval

We love our props here at Hackaday, and whenever we come across a piece from the Back To The Future fandom, it’s hard to resist showcasing it. In this case, [Xyster101] is showing of his build of Doc Brown’s Flux Capacitor.

[Xyster101] opted for a plywood case — much more economical than the $125 it would have cost him for a proper electrical box. Inside, there’s some clever workarounds to make this look as close as possible to the original. Acrylic rods and spheres were shaped and glued together to replicate the trinity of glass tubes, 3/4″ plywood cut by a hole saw mimicked the solenoids, steel rods were sanded down for the trio of points in the centre of the device and the spark plug wires and banana connectors aren’t functional, but complete the look. Including paint, soldering and copious use of hot glue to hold everything in place, the build phase took about thirty hours.

The LEDs have multiple modes, controlled by DIP switches hidden under a pipe on the side of the box. There’s also motion sensor on the bottom of the case that triggers the LEDs to flicker when you walk by. And, if you want to take your time-travel to-go, there’s a nine volt plug to let you show it off wherever — or whenever — you’re traveling to. Check out the build video after the break.

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Hackaday Prize Entry: Micro Matrix Charlieplexed Displays

If you need a very thin, low power display that doesn’t use a whole bunch of pins on your microcontroller, [bobricius] has just the thing for you. His entry to the Hackaday Prize this year is a Charlieplexed LED display. With this board, you can drive 110 LEDs using only 11 GPIO pins.

Charlieplexing is a bit of a dark art around these parts. That’s not to say the theory is difficult; it’s really just sourcing or sinking current from a GPIO pin and arranging LEDs unparallel to each other. The theory is one thing, implementation is another. To build a Charlieplexed LED matrix, you need to go a bit crazy with the PCB layout, and god help you if you’re doing this point-to-point on a perf board.

Somehow, [bobricius] managed to fit 110 LEDs on a PCB, all while managing to break out those signal wires to a sensible set of pads on one side of the board. Only eleven pins are required to drive all these LEDs, making this project a great foundation for some very cool wearables or other projects that require a bright, low-res display.

Since [bobricius] can put 110 LEDs on a small board, he can obviously take LEDs away from that board. That’s what he did with his cut down version designed to be a clock. Both are great little boards, and the perfect solution for tiny displays for low-pin-count micros.

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Boost Converter Functionality at Rock-Bottom Prices

Linear voltage regulators are pretty easy to throw into a project if something in it needs a specific voltage that’s lower than the supply. If it needs a higher voltage, it’s almost just as easy to grab a boost converter of some sort to satisfy the power requirements. But if you’re on a mission to save some money for a large production run, or you just like the challenge of building something as simply as possible, there are ways of getting voltages greater than the supply voltage without using anything as non-minimalistic as a boost converter. [Josh] shows us exactly how this can be done using a circuit known as a charge pump to drive a blue LED.

One of the cool things about AVR microcontrollers is that they can run easily on a coin cell battery and source enough current to drive LEDs directly from the output pins. Obviously enough, if the LED voltage is greater than the voltage of the power supply, this won’t work. That is, unless you have a spare diode and capacitor around to build a charge pump.

The negative charge pump works by charging up a capacitor that is connected to an AVR pin, with the other side between the LED and a garden-variety diode to ground. That results in a roughly (VCC – 0.7) volt difference across the capacitor’s plates. When the AVR pin goes low, the other side of the capacitor goes negative by this same amount, and this makes the voltage across the LED high enough to light up. Not only is this simpler than a boost converter, but it doesn’t need any bulky inductors to work properly.

Will this work for any load? Am I going to start any fires by overdriving the LED? Luckily, [josh] answers all of these questions and more on the project page, and goes into some detail on the circuit theory as well. Granted, the charge pump doesn’t have the fine control over the power supply that you can get out of a buck or boost converter (or any switch-mode power supply). But it does have good bang-for-the-buck.

Daunting Interactive LED Dancefloor Build is Huge Win

If you’ve ever thought about having a light-up dance floor at an event, the chances are you will have been shocked at the rental cost. Doing your best impression of a young John Travolta in Saturday Night Fever doesn’t come cheap, it seems. When faced with this problem before the Furnal Equinox 2017 convention, [Av] and friends decided instead to build their own LED-lit floor.

Their design and build is shown in the video we’ve placed below the break, and though each individual light unit is straightforward it is the scale of the project and its epic build that makes it a very impressive achievement. There are 64 panels of 4 light cells, giving a total of 256 cells and 7680 RGB LEDs arranged as 2560 pixels. Each panel has a shift register PCB interfacing LEDs to the Teensy that controls the floor, and there are also microswitches talking to an Arduino Mega which provides the floor with interactivity. It’s hard to imaging this build would be possible without the people numerous who pitched in at the Toronto Hacklab for the assembly process.

The resulting 17 foot square dancefloor is a work of art, with custom programmed graphics responding to dancers moves, and even a few games along the lines of Dance Dance Revolution built in. After watching the video below, how many of you will secretly want one?

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Tiny Electric Motor Runs on Power from an LED

If you were not aware, LEDs can also work in reverse: they deliver tiny amounts of current, in the microamp range, when illuminated. If you look on YouTube you can find several videos of solar panels built with arrays of LEDs, but powering an electric motor with a single 3 mm LED is something that we’ve never seen before. [Slider2732] built a small electric motor that happily runs from a green LED in sunlight.

The motor uses four coils of 1,000 ohms each. Using coils with many turns of very fine wire helps to draw less current while keeping an appropriate magnetic field for the motor to run. To keep friction at a minimum, the rotor uses a needle that hangs from a magnet. Four neodymium magnets around the rotor are periodically pushed by the coils, generating rotation. A simple two-transistor circuit takes care of the synchronization and yes, the motor does run on the four microamps provided by the LED, and runs pretty well.

Building motors is definitely an enjoyable activity, these small pulse motors can be built in just a couple of hours. You can use coils with just a few tens of turns which are much more easy to make but of course you will need something more than four microamps! The nice part of making an ultralow current motor like this is that it can run for a very long time on a tiny battery or even a capacitor, we invite you to try building one.

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Can You Bull’s-Eye A Womprat With A Bean Bag?

As it turns out, a simple game of cornhole — aka, bean bag toss — can have some pretty high stakes. If you lose a round playing on this Death Star trench run cornhole table, the Rebel Alliance may pay the price.

Designed and built by [Hyperdynelabs], the table is set up to play a number of audio clips from the movie with accompanying light effects. Details on how it was made are scant, but there are at least three strips of RGBW LEDs — two that run the length of the board and one inside the exhaust port — an Arduino(presumably), and some sort of wireless connectivity to receive commands.

But it’s not just the electronic effects that make this one great. The physical build itself really nails the Death Star trench run look. This is thanks to artful use of greebles — it’s the same technique which can turn a Nissan into a Z-Wing.

When you make a shot worthy of Luke Skywalker, you’re treated to an impressive lightshow and the sound of the Death Star exploding. For a particularly bad turn, you can have the table charge up and make a show of firing back, or taunt the player if their shot goes wide.

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Build Your Own Animated Turn Signals

Automotive lighting used to be strictly controlled, particularly in the United States — anyone remember sealed beam headlamps? These days, pretty much anything goes. You can even have an animated turn signal, because a simple flash isn’t fancy enough these days. You can get a scanning-LED turn signal on your new model Audi, among others. [Shravan] wanted this on their Mazda and set about building an animated turn signal and daytime running lights setup for their car.

It’s not a complicated build by any means; an off-the-shelf WS2812B strip provides the blinkums, an Arduino Nano the smarts. Using a modified library to drive the LEDs allowed [Shravan] to get things running with a minimum of fuss. We’d love to see a little more of the gritty reality of this build — how the Nano is getting directional signals from the car, and how it’s all wired up and bolted on. When you’re installing custom hardware onto a vehicle, the devil really is in the details. It’s supremely difficult to create something that looks tidy and functions well.

It’s amazing to think about how far we’ve come. When high-brightness LEDs first came on to the market in the 1990s, you would have been on the hook for wiring your own loom to connect the 20+ LEDs, building your own driver circuitry, and likely etching a custom PCB — all the while you programmed a PIC in assembly as it dangled off a parallel-port programmer. But then again, our cave-dwelling ancestors didn’t even have matches. Time marches on. Use today’s technology to build the very best things you can.

We love seeing car mods, particularly those that are well executed. Check out [Dave]’s interior lighting mods to the Nissan Juke — a car this writer has weighty opinions about. Video after the break.

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