Cycling can be a risky proposition on busy urban streets or rural roads that aren't equipped with a bike lane. But in addition to wearing the usual safety gear to keep you visible, you can also now invest in a crowdfunded and affordable LIDAR ("LIght Detection And Ranging", or "Laser Imaging, Detection and Ranging") which can be modified to detect when a car is coming up from behind. LIDARs are similar to radar systems, but use long-range laser pulses instead of radio waves.
Using a USD $89 LIDAR-Lite system from PulsedLight (they've since put out a $115 version 2), Paul Wallich writes over at IEEE Spectrum how he was able to modify his LIDAR-Lite, which has a range of 40 metres (131 feet), by plugging it into an Arduino microcontroller, running the detector's free software, re-programming and 3D printing a custom protective case for it:
Though preliminary runs with his DIY early-warning system for cars prove that it does the job, Wallich is still in the process of tweaking it, noting that power consumption could be improved.
Into the shell I was able to fit the Lidar-lite, the microcontroller, and a little strip of Neopixel RGB LEDs that act as a warning display, with room for a uniform 6-millimeter layer of padding. (Of course, my first shell design didn’t fit on the back of the bike, but a few more iterations fixed that.) The bike mount built into the shell is tilted to point a few degrees upward and to the left, so that as the lidar beam diverges with distance it will be more likely to impinge upon approaching cars rather than just road surface and shrubbery.
For those of us who've never heard of LIDAR, it's the technology that the police use in determining which cars are speeding or not; it's used in self-driving cars, 3D surveying, atmospheric remote sensing and meteorology, astronomy, robots and even in the military. Here's a video explaining how LIDAR works in layman's terms:
But it's not all serious stuff -- some enterprising individuals have gone so far to create "laser air harps" or "laser theremins" with this technology.
From rapid cooling to super-fast wireless internet carried by laser-radio, what cool things can't lasers do? Read more of how this DIY early-warning car detection system was made over at IEEE Spectrum, and find out more about the LIDAR-Lite over at PulsedLight.