Bike Power Meter With Crank-mounted WiFi Strain Gauges

April 3, 2016 by 35 Comments

In any motorsport, the more you know about how the engine is performing, the better a driver is likely to do in a race. That holds for bicycles, too, where the driver just happens to also be the engine. There are plenty of cheap bike computers on the market, but the high-end meters that measure power output are a bit pricey. [chiprobot] is looking to change that with a home-brew, low-cost bike power meter.

The project still appears to be in the proof-of-concept phase, but it’s an interesting concept for sure. The stock crank arms are carefully fitted with two pairs of tiny strain gauges. The gauges are wired in a Wheatstone bridge arrangement, with one gauge in each pair mounted perpendicular to the force on the crank to serve as a static reference. Output from the bridge is fed to an HX711 instrumentation amplifier. The demo video below shows how sensitive the bridge and 24-bit amp are.

The goal is to send crank data to a handlebar-mounted UI via WiFi with a pair of ESP8266 modules. We like the idea of a bicycle area network, but [chiprobot] has his work cut out for him in terms of ruggedizing and weatherproofing all this gear. We’ll be sure to keep an eye on this project. In the meantime, there’s plenty to learn from this bike power meter project we covered last year.

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Raspberry Pi As Speed Camera

April 3, 2016 by 110 Comments

Wherever you stand on the topics of road safety and vehicle speed limits it’s probably fair to say that speed cameras are not a universally popular sight on our roads. If you want a heated argument in the pub, throw that one into the mix.

But what if you live in a suburban street used as a so-called “rat run” through route, with drivers regularly flouting the speed limit by a significant margin. Suddenly the issue becomes one of personal safety, and all those arguments from the pub mean very little.

Sample car speed measurements
Sample car speed measurements

[Gregtinkers]’ brother-in-law posted a message on Facebook outlining just that problem, and sadly the local police department lacked the resources to enforce the limit. This set [Gregtinkers] on a path to document the scale of the problem and lend justification to police action, which led him to use OpenCV and the Raspberry Pi camera to make his own speed camera.

The theory of operation is straightforward, the software tracks moving objects along the road in the camera’s field of view, times their traversal, and calculates the resulting speed. The area of the image containing the road is defined by a bounding box, to stop spurious readings from birds or neighbours straying into view.

He provides installation and dependency instructions and a run-down of the software’s operation in his blog post, and the software itself is available on his GitHub account.

We’ve had a lot of OpenCV-based projects but haven’t featured a speed camera before here on Hackaday. But we have had a couple of dubious countermeasures, like that humorous attempt at an SQL injection attack, or a flash-based countermeasure.

Turning An Angle Grinder Into A Belt Sander

April 3, 2016 by 23 Comments

Faced with a project requiring a lot of sanding, [George] had two options. Suck it up and buy a belt sander — or re-purpose a tool he already had to do the same job. He chose the latter, and turned an angle grinder into a belt sander.

Part of a series called Make It Extreme on YouTube, [George] built the entire project from scratch using raw materials. Using a lathe he created the aluminum rolling dowels the sanding belt will sit on. He pressed bearings into them, and then welded up a frame using scrap steel to hold them apart. He’s even added a spring-powered tension device to ensure the belt stays on.

As for mounting the angle grinder in place, it couldn’t be easier. It slides in between two metal guides, and attaches using the threaded hole for the angle grinder’s handle.

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Paper Enigma Machine

April 2, 2016 by 6 Comments

It was high-tech encryption for an important period of time in the mid-1940s, so perhaps you can forgive us our obsession with the Enigma machine. But did you know that you can make your very own Enigma just using some cut out paper strips and a tube to wrap them around? Yeah, you probably did. But this one is historically accurate and looks good too!

If you just want to understand how the machine worked, having a bunch of paper rolls in your hands is a very intuitive approach. Alan Turing explained the way it worked with paper models too, so there’s no shame there. With this model, you can either make the simple version with fixed rotor codes, or cut out some extra slip rings and go all out.

What is it with Hackaday and the Enigma machine? Just last month, we covered two separate Enigma builds: one with a beautiful set of buttons and patch cables, and another in convenient wrist-watch format. In fact, one of our first posts was on a paper Enigma machine, but the links are sadly lost to bitrot. We figure it’s cool to repeat ourselves once every eleven years. (And this one’s in color!)

Hack Corporate Overlords For Single Button Beer Delivery

April 2, 2016 by 9 Comments

[Brody Berson] is at it again, but this time he’s hacked the services floating in the aether around him to give him beer on demand. Finally the future we’ve been waiting for.

This hack is not as hacky as his first one, which, at the push of a button, could summon a bad driver straight to his house who would then give him pizza. The first one was done with a modified version of a button used to summon paper towels; because there’s nothing like needing paper towels RIGHT NOW, and then pushing a button to get them a few days later.

Apparently Amazon saw how practically no one was pushing the dish detergent button, but a lot of people were making scary mailboxes and magic pizza apps after ruthlessly scratching the branding off. So they shrugged and decided to sell the buttons as the newly branded (these get more hilarious when you don’t use the acronyms) Amazon, Amazon Web Services Internet of Things Button. Now your button can die along with the internet because Amazon is hosting your Raspberry Pi for a small fee, neat.

Anyway, [Brody] did some research on the best beer delivery services in his area, and went with one called Drizzly because they had a nice API. After integrating this system with Amazon’s, he can now push a button and minutes later, after subtracting some currencies from his account, a bad driver will show up and hand him beer.

MRRF: Tasty Filament From Proto-Pasta

April 2, 2016 by 21 Comments

Alongside printers from all walks of manufacturing, one can naturally expect to find people selling different kinds of filament at a 3D printing festival. One of these purveyors of plastic was Proto-pasta out of Vancouver, WA. Proto-pasta prides themselves on unique offerings and complete transparency about their manufacturing processes.

Almost all of their filaments are either PLA or HTPLA with something special added during extrusion. The menu includes steel, iron, carbon, and finely ground coffee. The coffee filament was one of our favorites for sure. The print they brought with them looked solidified light roast and had a transparent kind of lollipop quality to it. I couldn’t detect the coffee scent due to allergies, but [Alex] assured me that printing with this filament will make your house or hackerspace smell terrific.

[Alex] was giving away samples of their stainless steel composite PLA. This one can be polished to a smooth shine with a series of papers that run from 400 to 8,000-grit. Another of their newer offerings is PLA infused with magnetic iron particles. Prints made with this stuff can be rusted to achieve an antique, steampunk, or shabby chic aesthetic.

Proto-pasta also has an electrically conductive composite carbon PLA. This one is great for capacitive applications like making a custom, ergonomic stylus or your own game controller. According to the site, the resistivity of printed parts is 30 ohms per centimeter as measured perpendicular to the layers, and 115 ohms along the layers.

Have you made anything awesome with conductive or magnetic filament? Have you had any problems with unorthodox filaments? Let us know in the comments.

Hack Your Multimeter

April 2, 2016 by 28 Comments

A good multimeter (or a few of them) is an essential part of anyone’s electronics workbench. The only thing more useful than a multimeter is a logging multimeter that can take recordings over time. And the only thing more useful than that is one that can transfer that data back to your computer for analysis. But fancy meters often cost a bit of money.

[Kerry Wong] decided to take matters into his own hands and hack a serial-out port into his relatively inexpensive multimeter, giving him the ability to record anything the meter can measure roughly three times a second until he runs out of hard-drive space.

Our hack begins with the datasheet for the meter’s microprocessor. [Kerry] then tacked on a few wires, and dumped, modified, and reflashed the calibration and configuration EEPROM. With a single bit-flip in the EEPROM, he enabled serial output. With a few more, he made the backlight stay on longer, disabled auto power-off, and basically customized the meter the way he wanted it.

IRLink-400x202Getting the data out of the meter is the big coup, however. Not wanting to risk the computer that he’s connecting to the meter, [Kerry] knew that he needed optoisolation between the meter and the USART. He went with a beautifully minimal solution — simply wiring the meter’s serial output to an IR LED. Usually, transmitting data over IR is done by modulating the signal with a 38 kHz carrier for noise immunity. [Kerry] was going to put the receiver right up against the transmitter anyway, so he went with a plain IR photodiode on the PC side. sigrok takes care of the datalogging and display.

Adding more automation to our measurement bench has been on our to-do list for a long time now, and [Kerry]’s hack provides an inexpensive and fun way to get started. It’s the perfect companion to a computer-controlled supply. (Or two!.)