Parametric 3D Printable Wheels And Treads

When it comes to robotic platforms, there is one constant problem: wheels. Wheels have infinite variety for every purpose imaginable, but if you buy a wheeled robotic chassis you have exactly one choice. Even if you go down to the local Horror Freight, there’s only about five or six different wheels available, all of which will quickly disintegrate.

To solve this problem, [Audrey] created OpenWheel, a system of parametric, 3D-printable wheels, tweels, tires, and tracks for robotics and more.

Like all good parametric 3D-printable designs, OpenWheel is written in OpenSCAD. These aren’t 3D designs; they’re code that compiles into printable objects, with variables to set the radius, thickness, diameter of the axle, bolt pattern, and everything else that goes into the shape of a wheel.

Included in this toolset are a mess of wheels and gears that can be assembled into a drivetrain. 3D-printable track that can be printed out of a flexible filament for something has been almost unobtanium until now: completely configurable 3D-printable tank treads. All we need now is a 3D-printable tank transmission, and we’ll finally have a complete hobby robotics chassis.

DIYing A Raspberry Pi Power Bank

Over the last decade or so, battery technology has improved massively. While those lithium cells have enabled thin, powerful smartphones and quadcopters, [patrick] thought it would be a good idea to do something a little simpler. He built a USB power bank with an 18650 cell. While it would be easier to simply buy a USB power bank, that’s not really the point, is it?

This project is the follow-up to one of [patrick]’s earlier projects, a battery backup for the Raspberry Pi. This earlier project used an 14500 cell and an MSP430 microcontroller to shut the Pi down gracefully when the battery was nearing depletion.

While the original project worked well with the low power consumption Pi Model A and Pi Zero, it struggled with UPS duties on the higher power Pi 3. [patrick] upgraded the cell and changed the electronics to provide enough current to keep a high-power Pi on even at 100% CPU load.

The end result is a USB power bank that’s able to keep a Raspberry Pi alive for a few hours and stays relatively cool.

The Future Travels Of The Travelling Hackerbox

For the past year, I’ve been organizing a very special project over on hackaday.io. It’s the Travelling Hacker Box, a box full of random electronics junk, sibling to the The Great Internet Migratory Box Of Electronics Junk, and a project that has already traveled more than 25,000 miles. Earlier this month, I said the Hackerbox is going international, I asked for contributors to receive the project in faraway lands, and now it’s time for the final report. This is where the Travelling Hackerbox will be going over the next year.

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The Travelling Hackerbox Is Going International

Over the last year, Hackaday.io has seen an incredible project. It’s a migratory box of random electronic junk, better known as the Travelling Hackerbox. The idea behind this mobile electronic surplus store is simple: receive the box, take out some cool electronic gizmos, add some of your own, and send it on to the next person on the list. It is the purest expression of the hacker aesthetic, all contained in a cardboard box.

The previous travels of the Travelling Hackerbox
The previous travels of the (second) Traveling Hackerbox

Last week, the Travelling Hackerbox appeared at the Hackaday Superconference where it was torn asunder. Its silicon and plastic innards were spilled for a badge hacking competition. The body of the box is gone from this world but the spirit lives on. Parts were collected, pins straightened, the contents of anti-static bags condensed, and now it’s time for the Travelling Hackerbox to leave the nest. It’s going down to the post office, sending in its passport application, and it’s finally heading out into far-flung lands that are not the United States.

Over the last year, and despite some jerk in Georgia, the Traveling Hackerbox has racked up the miles. From Maine to Flordia, and from Alaska to Hawaii, the Hackerbox has distributed parts to dozens of labs and workstations. If you want to get an idea of the box, the last recipient, Carl Smith, put together a great summary and photo log of what he found in this magical box.

I’ve always promised the Hackerbox would go international after racking up 25,000 miles – the distance around Earth’s equator. Now, it’s finally time. This is happening, and I’m looking for volunteers to take care of the box.

How this is going to go down

Right now, the Travelling Hackerbox is sitting at the Hackaday Overlords office in Pasadena. The next trip will be to Canada, hopefully around Vancouver, where it will eventually make it to the Maritimes. From there, the box will travel to Europe (West to East, possibly ending in Russia). The box will then travel through Africa, ending South Africa, and head over the Indian Ocean to Australia. The rest of Oceania, Southeast Asia, India, and China will be next, possibly followed by South and Central America. With any luck, the Travelling Hackerbox will arrive back at home base by next year.

Of course, this all depends on how many members of the hackaday.io community would like to receive the box and where those people are located. If you want to receive the box, this is the sign-up form [the sign up form is now closed]. This form will be open for the next week, afterwards I will look at the responses, consider each of them, and plan this epic trip around the world.

The current state of the box

The Travelling Hackerbox was originally based on a US Postal Service flat rate box. Because flat rate boxes are for US destinations only, the physical manifestation of the box must change. At the very least, this gives me an opportunity to laminate a new box in packing tape and reinforce the edges of the cardboard.

The new body for the Travelling Hackerbox is a 12x12x3 inch (about five liters) cardboard box, lovingly protected and reinforced with stickytape. This does reduce the overall volume of the somewhat, which required the disposal of a few parts that weren’t really cool. I assure you, nothing of great value was lost, and I only removed the larger, bulkier components I remember seeing the last time I had it.

All the coming travels will be planned next week when I get a few submissions to the international sign-up form.

Bending the Light

Ruled Hyperboloid CC Prof. William McCallum
Ruled Hyperboloid CC Prof. William McCallum

Everyone knows you can’t visibly bend light over short distances in free air. Or can you? [Jack Pearse] has figured out a way to do it though, or at least make it appear that way. He does it by combining a trick of math and a trick of the eye. The secret is the hyperboloid, a geometric construct described by a quadratic equation. [Jack’s] creation is more specifically a hyperboloid in one sheet. This type of structure allows straight lines to create a an overall curved surface.  Hyperboloids have been used by architects and in construction for years, often in tall structures like water towers.

If a bunch of straight steel beams can form a curved shape, lasers should be able to pull off the same effect. By employing persistence of vision, [Jack] was able to create his hyperboloid with only 10 small lasers. The lasers are mounted on the rim of a bicycle wheel and carefully aimed. The wheel is spun up with using an electric bicycle motor. [Jack] kept things safe by building a centrifugal switch. The switch powers up all the lasers in when the tire is spinning. This ensures no one can be hit by a static beam.

Once the wheel is spinning, all you need is a bit of smoke or haze in the room. The spinning lasers combine to form the hyperboloid shape. You can see the project in action in the video after the break.

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Retrofitting Smoke Alarms With Bluetooth

Everybody should have a few smoke alarms in their house, and everyone should go check the battery in their smoke alarm right now. That said, there are a few downsides to the traditional smoke alarm. They only work where you can hear them, and this problem has been solved over and over again by security companies and Internet of Things things.

Instead of investing in smart smoke alarms, [Johan] decided to build his own IoT smoke alarm. It’s dead simple, costs less than whatever wonder gizmo you can buy at a home improvement store, and reuses your old smoke alarm. In short, it’s everything you need to build an Internet-connected smoke alarm.

Smoke alarms, or at least ionization-based alarms with a tiny amount of radioactive americium, are very simple devices. Inside the alarm, there’s a metal can – an ionization chamber – with two metal plates. When smoke enters this chamber, a few transistors sound the alarm. If you’ve ever taken one apart, you can probably rebuild the circuit from memory.

Because these alarms are so simple, it’s possible to hack in some extra electronics into a design that hasn’t changed in fifty years. For [Johan]’s project, he’s doing just that, tapping into one of the leads on the ionization chamber, measuring the current through the buzzer, and adding a microcontroller with Bluetooth connectivity.

For the microcontroller and wireless solution, [Johan] has settled on TI’s CC2650 LaunchPad. It’s low power, relatively cheap, allows for over the air updates, and has a 12-bit ADC. Once this tiny module is complete, it can be deadbugged into a smoke alarm with relative ease. Any old phone can be used as a bridge between the alarm network and the Internet.

The idea of connecting a smoke alarm to the Internet is nothing new. Security companies have been doing this for years, and there are dozens of these devices available at Lowes or Home Depot. The idea of retrofitting smarts into a smoke alarm is new to us, and makes a lot of sense: smoke detectors are reliable, cheap, and simple. Why not reuse what’s easy and build out from there?

Maslow Brings The Wall Plotter Into The Woodshop

Hanging plotters, or two steppers controlling a dangling Sharpie marker on an XY plane, are nothing new to our community. But have you ever thought of trading out the Sharpie for a wood router bit and cutting through reasonably thick plywood sheets? That would give you a CNC machine capable of cutting out wood in essentially whatever dimensions you’d like, at reasonably low-cost. And that’s the idea behind [Bar]’s Maslow. It’s going to be a commercial product (we hope!), but it’s also entirely open source and indubitably DIYable.

[Bar] walks us through all of the design decisions in this video, which is a must-watch if you’re planning on building one of these yourself. Basically, [Bar] starts out like any of us would: waaaay over-engineering the thing. He starts out with a counterweight consisting of many bricks, heavy-duty roller chain, and the requisite ultra-beefy motors to haul that all around. At some point, he realized that there was actually very little sideways force placed on a sharp router bit turning very quickly. This freed up a lot of the design.

His current design only uses two bricks for counterweights, uses lighter chains, and seems to get the job done. There’s a bit of wobble in the pendulum, which he admits that he’s adjusted for in software. Motors with built-in encoders and gearing take care of positioning accurately. We haven’t dug deeply enough to see if there’s a mechanism to control the router’s plunge, which would be great to cut non-continuous lines, but first things first.

Taking the wall plotter into the woodshop is a brilliant idea, but we’re sure that there’s 99% perspiration in this design too. Thanks [Bar] for making it open! Best of luck with the Kickstarter. And thanks to [Darren] for the tip.