Brilliant Auto-off Feature For A Bike Light

February 6, 2013 by Mike Szczys 30 Comments

auto-off-bike-light-switch

If you’re going to use your bicycle as transportation at night you really must have a head and tail light in hopes that the crazy drivers don’t hit you. For good reason, these lights don’t turn themselves off. But [Miceuz] kept forgetting to shut it down upon arrival and always ended up with dead batteries. His quest for an auto-off feature that actually worked ended in a brilliant and simple add-on circuit.

He first thought about using an accelerometer, but couldn’t find one that fit the bill without also adding a microcontroller. He came up with an even simpler circuit, which can be seen at the base of the black plastic housing. It’s a bit of copper clad board with a small spring attached. The spring completes an RC timer circuit which drives a MOSFET. When that circuit is charged, the MOSFET connects power to the bike light. When the cap runs out the MOSFET threshold cuts power and everything turns off. Since the spring jiggles while he rides it provides the momentary connection necessary to charge the capacitor. Stay stationary for about 30 seconds and the auto-off kicks in.

Adapting The Nexus 7 For A Double DIN Car Dashboard Opening

January 29, 2013 by Mike Szczys 33 Comments

It turns out that the Nexus 7 Android tablet is the perfect size to fit in a double DIN opening. DIN is the form factor of a single CD head unit for an automobile. Many models have room for a double DIN, which is defined as 4″ high by 7″ wide. Once [Meta James] figured out that the dashboard bezel for his Subaru framed the Nexus 7 perfectly he set out to fabricate the mounting system for an in-dash tablet installation.

Unlike a lot of these dashboard tablet installs, [James] didn’t need any Bondo, sanding, or painting to get things to look right. Like we mentioned, the bezel is a perfect fit so his alterations are hidden behind the tablet itself. He removed the stock head unit and ordered a DIN adapter kit to get the black bracket plate seen above. He built an acrylic box the same size as a double DIN head unit, then mounted the plates to the sides and a Nexus 7 case to the front. This holds the tablet in firmly, lets him mount the entire assembly using the factory mounting points, and leaves plenty of room for the cabling that connects the device to the car. Since he already had a hands-free phone system he just uses that to amplify the audio fed to it via Bluetooth.

[via Reddit]

Wooden Cargo Bicycle

January 24, 2013 by Mike Szczys 10 Comments

nearlycomplete

This is a cargo bicycle made almost completely out of wood. [Niels] and three of his classmates built it at Wico Campus Tio, a science and technology school in Dorpsstraat, Belgium. There’s a lot to be impressed by in this build. Sure, the guys concede that not everything is wood. They used metal screws as well as hubs, a crank shaft, and gears from a bicycle (not seen in this image). But everything else was made from Beech or Padouk wood. This includes the leaf springs that help cushion the cargo box from the bumps in the road.

The box itself acts as the handlebars. You can see the bracket which holds one end of a dowel spanning the left side of the box. This image was taken before the seat and cranks were added, but once they’re in place the front axle will turn along with the box for steering.

You can get a good look at the finished bike in the video after the break. You’ll also find a link to the Power Point slides there. Since that presentation is in Dutch we translated the text and pasted it below.

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Faceless Child’s Engineer Father Builds Him A Breathtaking Ride

January 22, 2013 by Mike Szczys 56 Comments

amazing-kids-car

Okay, the kid does have a face, but it looks like Dad blurred it for his protection. The real story here is the killer ride built by his engineer father. It’s far nicer than the cars driven by the Hackaday team, but then again, since it cost more than a BMW 3 series that’s no surprise.

[Lingzi] lives in China and does custom car work for a living. So to take on this project for his son was more of a stretch of the pocketbook than of his skill set. The car features a custom frame with rack and pinion steering, disc brakes, a rear differential, and a reputable suspension system. The body of the vehicle is crafted from carbon fiber. The lights all work and there’s an electric motor and transmission mounted just behind the driver’s seat. Unfortunately there’s no video of this in action (China blocks YouTube). But do take a look at the album above for pictures of the final paint job. There is also a little bit more information to be found in [Lingzi’s] Reddit discussion.

Building An Automatic Bicycle Transmission In A Week

January 18, 2013 by Brian Benchoff 58 Comments

Every year, the ECE department of Carnigie Mellon University hosts Build18, an engineering festival intended to get students out of the classroom and into the workshop. [Andrew Toth] along with team members [Jenna MacCarley], [Peter McHale], and [Nicolas Mellis] have been busy this last week putting together an automatic bicycle transmission.

Most cyclists agree that a cadence of 80 RPM is just about right for most cycling. The team’s transmission uses Hall effect sensors to sense the cadence of the rider and will change to a higher gear if the cadence drops below 60 RPM and a lower gear if the cadence is above 100 RPM.

One of the requirements of the Build18 festival is the completed project must cost less than $250. By using an Arduino Mega and a servo to change gears, the team has a fairly low cost solution to automatically changing bicycle gears.

It’s a very cool project, and hopefully we’ll see a video once the competition is over at noon, EST today.

Retrotechtacular: The Differential

January 15, 2013 by Mike Szczys 22 Comments

Any video that starts off with two minutes of motorcycle formation riding has got to be good. If the grainy black and white video didn’t tip you off that this was made in a different time the helmetless riders standing on the seats of moving motorcycles certainly would have. But there is a purpose to this exposition. A single line of motorcycles riding shoulder to shoulder as they go around a curve illustrates why a differential is necessary and soon after you’ll find out how one works.

Two wheels mounted on one axle need to turn at different speeds as a vehicle goes around a corner or one of the wheels must slip to accommodate the speed difference. The differential is necessary to allow for these different turning rates while still letting both wheels connect to the power train. We were surprised to learn from the video after the break that early automobiles got around this issues by powering only one of the four wheels.

This instructional video is a prefect compliment to the fluid coupling video we saw in the last installment of Retrotechtacular.

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Another Take On The Rear-window LED Marquee

January 9, 2013 by Mike Szczys 40 Comments

re-window-led-display

This rear-window LED marquee will help let the driver behind you know when you’re planing to change lanes or make a turn. But it also includes the ability to send a message like “Back Off!”. [Robert Dunn] was inspired to undertake the project after seeing the one we featured back in October. We’d say his has a better chance of being street legal since it uses all red LEDs.

The marquee is a matrix of 480 LEDs, all hand soldered to form the nearly transparent 48×10 grid shown above. This is important to preserve visibility out the back window of his truck. It makes us wonder about the feasibility of using SMD instead of through hole components. That would certainly make it even less visible when not illuminated, but the assembly process would be much more difficult. That’s because the 5mm LED packages fit nicely in the grid of holes he drilled in some plywood which served as the jig during soldering. The presence of leads also made the soldering process manageable.

Power to an Arduino board is provided from the cigarette lighter adapter. A set of six shift registers drive the columns while the rows are controlled by a 4017 decade counter and some transistors. Check out the blinker test video after the break to get a look at what this can do while on the road.

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