Sluggy Wind Speed Sensor

Sometimes when we look at a hack, its to see how someone chose those parts for the project. In this case, it would have been hard to see it coming. [Janne Jansson] decided to combine a set of measuring cups, a hacked Linksys NSLU2 NAS, and a PS/2 Mouse together to make a self-contained Wind Speed Sensor for his roof. The measuring cups act as wind catchers, which in turns drives the rotation of one of the mouse ball sensors. This data is then logged and transmitted by the NSLU2. The NSLU2 is running a custom Linux based firmware, similar to how OpenWRT works for wireless routers.

To calibrate the device, he also made the best logical choice: to duct tape it to the hood of his car along with a much more expensive wind sensor and use that data to make his own device as accurate as possible. When placed atop his house with a 1500VA 220V UPS, the device managed 250 days of uptime before meeting its demise. Those 250 days also included 5 days of being frozen solid, yet still transmitting (somewhat meaningless) data. All of the relevant code and build instructions are available, for those of you with similar parts to spare.

Maze-solving robo mouse

Looking for something to build that will be challenging and interesting to laypersons at the same time? Take some inspiration from this maze-solving robot mouse. It take the idea of a line-following robot, and makes it infinitely more cool. The tiny rover uses sensors to map out a physical maze. Once it figure it out, you put it back at the beginning for a speed run to the finish. We’ve embedded the video below showing the whole process. Looks like the speed-run is completed in just under five seconds.

Now that you’ve enjoyed a virtual mouse in a real maze, check out a real mouse in a virtual maze.

Continue reading “Maze-solving robo mouse”

Projectile speed sensor

[Mike] built a sensor rig to measure projectile speed. The setup uses a tunnel with two sensors in it. Each consists of a laser diode on one side focused on a photodiode in the other. The two are monitored by an op amp and measured by an ATmega128 microcontroller. When the beams are broken the elapsed time between the two events is measured in order to calculate speed. There is a setting to adjust the calibration for a range of speeds, which came in quite handy as [Mike] initially tested the device with rubber bands before moving on to a pellet gun and then a rifle.

It seems like he’s tempting fate by shooting a target just a few inches below his exposed circuitry but his marksmanship prevailed. We’ve seen bullet speed detectors in the past, used just for the delight of seeing how fast the projectile is moving, and also to capture an impact at just the right instant.

A cop in every car

[Michael] designed this display board to mimic the appearance of a police car pulling you over. It resides in the rear window of his car (facing forward) as the controller board measures the speed of the vehicle. An Arduino grabs NMEA data from a GPS module and compares it with a table of speed limits. If you are speeding, based on your current location, the reds and blues flash as if you’re getting pulled over. The thrill of getting busted for a lead foot doesn’t sound like much fun to us but to each his own.

Incidentally, [Michael] is using the EM406 GPS module, the same one as the Frustromantic Box used.

PHP runtime rewritten, by Facebook?

Yes, its true. Facebook has completely rewritten the PHP runtime to make it faster and more efficient, and its completely open source. Named HipHop, its described as a source code transformer, changing PHP into optimized C++ which is then compiled using g++. Thus keeping the best aspects of PHP while taking advantage of the performance of C++. Using HipHop, the Facebook web server CPU usage has been decreased by about fifty percent! And who would have thought that this and many other cool advances in programming, started at a Hackathon.

Bike trainer computer: Speed, Cadence, Heartrate, Trainer temp

[Kurt] was using a bike trainer to get in shape for warmer and dryer biking months. Unfortunately it’s pretty hard to train if you don’t have reliable data concerning how hard you’re working. There’s commercial solutions for trainer computers but he’d read some rough reviews about them and decided to build his own trainer computer. He’s done a great job of integrating a lot of different data collection sources. He picked up two replacement bike computer sensors to use on the back wheel for speed (the front wheel is stationary with this type of trainer) and on the crank for cadence. He also wears a heart rate monitor and sourced a SparkFun heart rate module to gather that data. Finally, an LM235 analog temperature sensor was combined with a spring clamp to detect the temperature of the trainer’s resistance module.

Data from the sensors is collected with a PIC16F73 microprocessor and fed to a computer over a serial connection. He’s got a screenshot of the realtime graphs that he’s using for feedback while on the bike. This is a useful and practical setup but when he get’s tired of exercising he’s just a few lines of code from converting this into a gaming controller.

[Thanks Justin]

Capturing bullet speed

Sometimes it’s amazing how slow our sense of time is. We find [Maurice’s] bullet capture system a great example of this. A pair of IR sensors spaced two inches apart can capture and calculate the speed of a projectile. Couple this with a user-input distance from the sensor to the target and a microcontroller can extrapolate the exact moment to trigger a camera to catch a bullet in mid-air.

As with his other projects, all the details on how to build and use this system are available for your perusal.