It can be hard enough to take a good photograph of a running kid or pet, and if we’re being honest, sometimes even stationary objects manage to allude our focus. Now imagine trying to take a picture of something moving really fast, like a bullet. Trying to capture the moment a fast moving projectile hits an object is simply not possible with a human behind the shutter button.
Enter the ballistic chronometer: a device that uses a set of sensor gates and a highly accurate timer to determine how fast an object is flying through it. Chronometers that operate up to a couple hundred meters per second are relatively common, but [td0g] had something a little faster in mind. He’s come up with an optical setup that he claims can capture objects moving as fast as Mach 2. With this chronometer tied into a high-speed flash rig, [td0g] is able to capture incredible shots such as the precise instant a bullet shatters a glass of water.
Because he couldn’t find any phototransistors with the sub-microsecond response time necessary to detect a small object moving at 1,000 m/s, [td0g] ended up using LEDs in a photoconductive configuration, where 27 VDC is applied backwards against the diode. Careful monitoring of voltage fluctuations across the diode allows for detection of changes in the received light level. To cut down on interference, [td0g] used IR LEDs as his light sources, reasoning there would be less ambient IR than if he used something in the visual range.
What really impresses with this build is the attention to detail and amount of polish [td0g] put into the design. From the slick angled bracket that holds the Arduino and LCD to the 3D printed covers over the optical gates, the final device looks like a professional piece of equipment with a price tag to rival that of a used car.
For the future, [td0g] plans on upgrading to faster comparators than he LM339’s he has installed currently, and springing for professionally done PCBs instead of protoboard. In it’s current state this is already a very impressive piece of kit, so we’d love to see what it looks like when it’s “finished”.
If you don’t need something quite this high end but still would like to see how fast something is going, we have covered chronometer builds to fit every budget.
Wanting to experiment with using optical mouse sensors but a bit frustrated with the lack of options, [Tom Wiggins] rolled his own breakout board for the ADNS 3050 optical mouse sensor and in the process of developing it used it to make his own 3D-printed optical mouse. Optical mouse sensors are essentially self-contained cameras that track movement and make it available to a host. To work properly, the sensor needs a lens assembly and appropriate illumination, both of which mate to a specialized bracket along with the sensor. [Tom] found a replacement for the original ADNS LED but still couldn’t find the sensor bracket anywhere, so he designed his own.
Continue reading “DIY Optical Sensor Breakout Board makes DIY Optical Mouse”
In need of a waveform generator for another project, [David Cook] crammed out the old turntable to modify it for a handy hack: By adding a simple reflectance sensor to the pickup he turned it into a waveform generator that optically plays back arbitrary waveforms from printed paper discs.
Continue reading “Turntable Turns Waveform Generator”
Everything is getting smaller all the time. Computers used to take rooms, then desks, and now they fit in your pocket or on your wrist. Researchers that investigate light sensors have known that individual diarylethene molecules can exist in two states: one where it conducts electricity and one where it doesn’t. A visible photon causes the molecule to be electrically open and ultraviolet causes it to close. But there’s a problem.
Placing electrodes on the molecule interferes with the process. Depending on the kind of electrode, the switch will get stuck in the on or off position. Researchers at Peking University in Beijing determined that placing some buffering material between the molecule and the electrodes would reduce the interference enough to maintain correct operation. What’s more the switches remain operable for a year, which is unusually long for this kind of construct.
Using chemical vapor deposition and electron beam lithography, the team produced over 40 working single molecule switches. These devices could be useful in optical computing and other applications. Future work will include developing multilevel switches comprised of multiple molecules.
If you want something more macroscopic, you might try using an LED to sense light. A switch is fine, but sometimes you want to generate a signal.