Bike alert tells drivers to back off

Bicycle commuters are often in a battle with drivers for space on the road. [Hammock Boy] does all of his commuting on two human-powered wheels, and is quite interested in not getting hit by a car. He decided to ply his hobby skills to build a device that helps keep him safe. It’s not just a tail light, it’s a sensor that shines brighter the closer a car is to the back of the bike.

The sensor portion is the ultrasonic range finder seen in the center of the protoboard. Surrounding it is a set of LEDs. Each is individually addressable with the whole package controlled by an Arduino. The sketch measures the distance between the back of the bike and whatever’s behind it. If there’s nothing, one Red led is illuminated. If there is an object, the lights shine brighter, and in different patterns as the distance decreases.

Certainly the next iteration could use a standalone chip without the need for the whole Arduino. This could even work with two battery cells and no voltage regulator. We also think the use of any other color than Red LEDs is suspect but we do love the concept.

LayerOne badge hacking twofer

Here’s a pair of LayerOne Badge hacks that actually included the RC as intended by the badge designers.

First up, we have the autonomous RC car built by [Arko]. He calls it Stanley Jr. as an homage to the Stanford DARPA Grand Challenge vehicle. It uses an Arduino shield to add a servo with an ultrasonic rangefinder on it. The lets the vehicle drive a bit, stop and scan the horizon, then drive some more. The hope is the rangefinder will keep it from running into anything. There’s a quick test run embedded after the break.

On the right is the badge hack which [Zjpahle] finished up after the contest was already over. He also chose to go with an Arduino shield, this time it’s an IMU board. But he added a standalone Arduino board to the vehicle which drives some EL wire (ground effects) and adds IR sensors to the front of the car. The IR sensors are for obstacle avoidance, and the IMU lets him tilt his badge for direction control.

We looked at the winner of the badge hacking competition on Wednesday. That hack didn’t involve the car, but used the badge as a Morse Code beacon.

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Quick and easy wildlife camera

This wildlife camera is really easy to put together. You should keep it in mind if you’re ever tying to figure out what’s eating the heads off of all of your tulips. [Revoltlab] put it together, and although there’s one fatal flaw in this particular system, the concept is quite sound.

The build uses a camera, paired with an ultrasonic range finder. When something passes within the pre-set distance for the sensor, a servo motor clicks the shutter button on the camera. It’s all driven by an Arduino and powered from a 9V battery.

If you watch the video after the break you’ll discover the flaw we mentioned. This is a disposable film camera and requires winding between pictures. That hasn’t been implemented yet. But we’ve got an old digital camera with a broken LCD screen which would be perfect for the job. We’d have to do a bit more work to turn the camera on before taking the picture though.

There are a couple of possible upgrades to the idea. [Revoltlab] mentions removing the IR filter from the camera and adding an infrared flash for night-vision shots. But we would also recommend ditching the servo motor for a simple remote shutter solution as a way to avoid scaring the wildlife with the motor noise.

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3D whiteboard without the whiteboard

This one is so simple, and works so well, we’d call it a hoax if April 1st hadn’t already passed us by. But we’re confident that what [William Myers] and [Guo Jie Chin] came up with exists, and we want one of our own. The project is a method of drawing in 3 dimensions using ultrasonic sensors.

They call it 3D Paint, and that’s fitting since the software interface is much like the original MS Paint. It can show you the movements of the stylus in three axes, but it can also assemble an anaglyph — the kind of 3D that uses those red and blue filter glasses — so that the artists can see the 3D rendering as it is being drawn.

The hardware depends on a trio of sensors and a stylus that are all controlled by an ATmega644. That’s it for hardware (to be fair, there are a few trivial amplifier circuits too), making this an incredibly affordable setup. The real work, and the reason the input is so smooth and accurate, comes in the MATLAB code which does the trilateration. If you like to get elbow deep in the math the article linked above has plenty to interest you. If you’re more of a visual learner just skip down after the break for the demo video.

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Investigating parking assist sensors

While his wife was out-of-town [James] jumped at the opportunity to do some snooping around with her Chevy Tahoe’s parking assist sensors. We can understand how pulling parts out of someone’s car would make them none too happy. But we find it hilarious that it’s a leased company car he’s tinkering around with. But we’re glad he did, the ten-page write-up he published about the project is a fascinating read.

You can see the control board above which is housed beneath the passenger seat. It uses a Freescale microcontroller to read from the four bumper-mounted ultrasonic sensors. But just looking at what parts are used obviously isn’t enough to satisfy a hacker’s appetite for knowledge. [James] busted out a CAN bus tool to sniff the data packets. These sensors use a custom chip designed by GM, utilizing a single wire communications system. He figures out the communication scheme and builds an mbed based test rig to read them directly.

[via Dangerous Prototypes]

Powering an Ultrasonic Transducer

[Lindsay] has a wonderful writeup about a new toy in the shop, an ultrasonic transducer. The 28kHz, 70W bolt-clamped Langevin transducer by itself is not much use, you need a power supply, a horn to focus the energy, and a way to tune it. [Lindsay] starts off by showing how to find out the resonant frequency of the transducer, designing and building a high voltage high frequency AC power supply, and how to design a horn.

Not missing the meaning of DIY [Lindsay] casts and machines a horn for the transducer with a high level of precision as this will also tune the horn to the correct frequency. Once some brackets are machined the whole setup is put through some fun experiments in water and lemonaide, but the real purpose is to drill fine holes in glass for his home made Panaplex displays.

Join us after the break for a short video.

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DIY ultrasonic plastic welding

Here’s something that may be of interest to all the reprappers, vacuum formers, and other plastic fabbers out there: ultrasonic welding of plastics. If you’ve ever wanted to join two pieces of plastic without melting them together with acetone or screwing them together, [circuitguru] is your guy.

Ultrasonic welder setups are usually reserved for companies that don’t mind spending tens of thousands of dollars on a piece equipment. There are smaller versions made for heat staking - melting plastic pillars into rivets on the work piece – and [circuitguru] was lucky enough a somewhat reasonable price.

Because the heat staking gun was a handheld unit, a rotary tool drill press was put to work. The end result is a relatively inexpensive way to join two plastic parts without screws, glue, or solvents. The bond is pretty strong, too. Check out the video after the break to see [circuitguru] join two pieces of a plastic enclosure and try to tear them apart.

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