High Speed Chronograph Looks Like Pro Gear

November 14, 2017 by Tom Nardi 22 Comments

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 elude 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 its 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.

UV Sensitive Filament As A Persistent Display

November 14, 2017 by Jenny List 32 Comments

Some of the hacks we feature are modifications of existing devices, others are ground-up builds of entirely new ones. And then there are the experiments, things that have to be worth trying because they just might work. In this final category we have [Matt]’s work with UV sensitive plastic to form the basis of a simple persistent display, which has created something best described as a proof-of-concept that shows promise, and definitely proves that he had an idea very much worth trying.

The idea makes use of a plastic that changes colour from white to purple when exposed to UV light. He 3D printed a waffle-like structure to locate over a 3×3 grid of UV LEDs, which he could then illuminate under the control of an Arduino Mini Pro. A short illumination changes the colour of the plastic above it, creating a “pixel” that persists for several seconds. In this he has created a working proof of concept for a very simple 3×3 matrix display, albeit rather an unwieldy one. The advantage the idea offers is that a relatively long time of display can be achieved for a relatively short LED illumination, giving a potential for power saving.

The proof-of-concept itself isn’t particularly useful, but from this idea it’s possible a larger display could be practically made. An array of surface-mount LEDs could perhaps illuminate a larger array of plastic to a greater resolution, it’s definitely an idea that was worth trying, and which shows promise for further pursuit. If you’d like to see it in action he’s posted a video, which we’ve placed below the break.

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Modern Technology For An Ancient Contest

November 12, 2017 by Kristina Panos 2 Comments

Certamen is a special class of high school quiz bowl tournament that’s focused solely on the classics. No, not Austen and Dickens, the actual classics. All the questions are about stuff like ancient Greek and Roman civilization and culture, classical mythology, and the finer points of Latin grammar. Like any other quiz bowl, the contestants use buttons to buzz in and answer the questions.

To win at Certamen, a team needs more than just a vast working knowledge of classical antiquity. They also have to be fast on the buzzer. The best way to do that is to practice with official equipment. But this is Hackaday, so you know what comes next: all the ones you can buy cost five times more than they should, so [arpruss] made an awesome open-source version for a fraction of the cost.

The practice machine consists of 12 arcade-style buttons connected to a control box. An Arduino Mega in the control box records the order of button presses as they arrive and displays a corresponding code on an LCD. A toggle switch selects between Certamen mode, where one button press locks out the rest of the team, and a Quiz mode with no lockout.

Our favorite thing about this build is the way [arpruss] took care of managing long cables, which was one of his main must-haves. The buttons are wired to the control box with Cat6 in three groups of four—one cable per table, one pair per chair. Our other favorite thing is the Easter eggs. Hold down the clear button on the control box when the system is booting and one of two things happens: either the buttons band together and turn into piano keys, or some Latin poetry appears on the screen.

[arpruss]’s 3D-printed buzzer bases look pretty slick. If Certamen practice ever starts to get out of hand, he might consider more robust packaging, like these Devo hat buttons.

Roll Your Own Arduino PWM

November 12, 2017 by Al Williams 18 Comments

Most projects are built on abstractions. After all, few of us can create our own wire, our own transistors, or our own integrated circuits. A few months ago, [Julian Ilett] found a problem using the Arduino library for PWM. Recently, he revisited the issue and used his own PWM code to fix the problem. You can watch the video below.

Of course, neither the Arduino library nor [Julian’s] code is actually producing PWM. The Atmel CPU’s hardware is doing the work. The Arduino library gives you a wrapper called analogWrite — especially handy if you are not using an Atmel CPU where the same abstraction will do the same work. The issue arose when [Julian] broke the abstraction to invert the PWM output.

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Automating A Bowl Feeder With Arduino

November 11, 2017 by Dan Maloney 5 Comments

Search for “bowl feeder” on Hackaday and you’ll get nothing but automated cat and dog feeders. That’s a shame, because as cool as keeping your pets fed is, vibratory bowl feeders are cooler. If you’ve seen even a few episodes of “How It’s Made” you’re likely to have seen these amazing yet simple devices, used to feed and align small parts for automated assembly. They’re mesmerizing to watch, and if you’ve ever wondered how parts like the tiny pins on a header strip are handled, it’s likely a bowl feeder.

[John] at NYC CNC is building a bowl-feeder with Arduino control, and the video below takes us on a tour of the build. Fair warning that the video is heavy on the CNC aspects of milling the collating outfeed ramp, which is to be expected from [John]’s channel. We find CNC fascinating, but if you’re not so inclined, skip ahead to the last three minutes where [John] discusses control. His outfeed ramp has a slot for an optical sensor to count parts. For safety, the Arduino controls the high-draw bowl feeder through an external relay and stops the parts when the required number have been dispensed.

We know, watching someone use a $20,000 CNC milling station might seem overkill for something that could have been 3D printed, but [John] runs a job shop after all and usually takes on big industrial jobs. Or small ones, like these neat color-infill machine badges.

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Stop Motion With The Time Glove

November 9, 2017 by Donald Papp 29 Comments

What do you get when you put an ultra-bright LED in the palm of a glove, and strobe it controlled by an accelerometer? A Time Control Glove! In creator [MadGyver]’s own words, it’s “just a stroboscope with frequency adjustment” but the effect is where all the fun is.

The Time Control Glove uses the stroboscopic effect, which many of us have seen used in timeless water drop fountains where the strobe rate makes drops appear to change speed, freeze in place, and even change direction. [MadGyver] made the entire assembly portable by putting it into a glove. An on-board accelerometer toggles the strobe in response to a shake, and the frequency is changed by twisting the glove left or right. The immediate visual feedback to the physical motions is great. The whole effect is really striking on the video, which is embedded below.

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Listening For Hand Gestures

November 1, 2017 by Al Williams 15 Comments

[B. Aswinth Raj] wanted to control a VLC player with hand gestures. He turned to two common ultrasonic sensors and Python to do the job. There is also, of course, an Arduino. You can see a video of the results, below.

The Arduino code reads the distance from both sensors — one for the left hand and the other for the right. This allows the device to react to single hand gestures that get closer or further away from one sensor as well as gestures involving both hands. For example, raising your left hand and moving it closer or further away will adjust the volume. The right hand controls rewind and fast forward. Raising both hands will start or stop playback.

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