Bullet Time On A Budget With The Raspberry Pi

Bullet time became the hottest new cinema effect after it burst on the scene in The Matrix (1999). Back then, the cutting edge special effects required serious hardware and serious processing power to do the job. These days, of course, things have moved along somewhat. [Eric Paré] is no stranger to a high-end setup, but wanted to see what could be done at the lower end of the market. (Video, embedded below.)

Rather then relying on a bank of expensive DSLRs, [Eric] decided to try building a bullet-time camera rig out of 15 Raspberry Pis, and the standard Raspberry Pi Camera. Whereas just one camera in one of his professional setups may cost well over $1000, this entire rig was likely built for less than that in its entirety.

Initial results were jerky and unappealing, but [Eric] persevered. One of the biggest problems was inaccuracy in the camera assemblies, as they were stuck on with thermal paste. With some custom mods and tweaks, [Eric] was eventually able to get things to a passable state. It also has the benefit, compared to a DSLR rig, that the cameras can be mounted much more closely together due to their small size.

Work is already underway to upgrade the rig to the new Raspberry Pi HQ Camera, which we’ve discussed before.

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Measure The Speed Of A Speeding Bullet

In the study of ballistics, you can do very little without knowing the velocity of a projectile. Whether you need to hit a target at over a mile, check if a paintball gun is safe for opposing players, or photograph high-velocity objects, you need a way to measure that velocity. [td0g] enjoys the challenge of photographing bullets impacts, and has created an open-source ballistic chronograph to help achieve this.

A rifle bullet punching through a wine glass, captured with the help of the chronograph

[td0g]’s design makes use of two light gates spaced some distance apart, and the time that an object takes to travel between the two is measured and used to calculate velocity. Most commercial ballistic chronographs also work in this way. [td0g] created the light gates using pairs of infrared photodiodes and LEDs. When there is a sudden dip in the amount of light received by the photodiode, the Arduino control circuit knows that an object has passed between the photodiode and LEDs and triggers the timer. An LCD shield on the Arduino is used to control the software and display velocity. As you probably guessed, clock accuracy is very important for such time measurements, and [td0g] demonstrates a simple technique using a smartphone metronome app to manually calibrate the clock to acceptable accuracy for his purposes. Continue reading “Measure The Speed Of A Speeding Bullet”

Rocket Bullets: The Flame And Fizzle Of The Gyrojet

In the 1950’s and 60’s, the world had rocket fever. Humankind was taking its first steps into space and had sights on the moon. Kids could build rockets at the kitchen table and launch them in the schoolyard. On the darker side, the arms race was well underway with the US and USSR trying to close the fictional missile gap.

All around the world, engineers were trying to do new things with rockets. Among these were Robert Mainhardt and Arthur T. Biehl, who thought rockets could be useful as small arms. Together they formed MBA (short for Mainhardt and Biehl Associates), with an eye toward future weapons – – specifically rocket bullets.

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Coming Back To Curving Bullets

What do you do when you have time, thousands of dollars worth of magnets, and you love Mythbusters? Science. At least, science with a flair for the dramatics. The myth that a magnetic wristwatch with today’s technology can stop, or even redirect, a bullet is firmly busted. The crew at [K&J Magnetics] wanted to take their own stab at the myth and they took liberties.

Despite the results of the show, a single magnet was able to measurably alter the path of a projectile. This won’t evolve into any life-saving technology because the gun is replaced with an underpowered BB gun shooting a steel BB. The original myth assumes a firearm shooting lead at full speed. This shouldn’t come as any surprise but it does tell us how far the parameters have to be perverted to magnetically steer a bullet. The blog goes over all the necessary compromises they had to endure in order to curve a bullet magnetically and their results video can be seen below the break.

Here we talk about shooting airplane guns so they don’t get mislead after leaving the barrel, and some more fun weaponry from minds under Churchill’s discretion.

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Hackaday Links: December 7, 2014

Have some .40 cal shell casings sitting around with nothing to do? How about some bullet earbuds? If you’ve ever wondered about the DIY community over at imgur, the top comment, by a large margin, is, “All of these tools would cost so much more than just buying the headphones”

Here’s something [Lewin] sent in. It’s a USB cable, with a type A connector on one end, and a type A connector on the other end. There is no circuitry anywhere in this cable. This is prohibited by the USB Implementors Forum, so if you have any idea what this thing is for, drop a note in the comments.

Attention interesting people in Boston. There’s a lecture series this Tuesday on Artificial Consciousness and Revolutionizing Medical Device Design. This is part two in a series that Hackaday writer [Gregory L. Charvat] has been working with. Talks include mixed signal ASIC design, and artificial consciousness as a state of matter. Free event, open bar, and you get to meet (other) interesting people.

Ghostbusters. It’s the 30th anniversary, and to celebrate the event [Luca] is making a custom collectors edition with the BluRay and something very special: the Lego ECTO-1.

Let’s say you need to store the number of days in each month in a program somewhere. You could look it up in the Time Zone Database, but that’s far too easy. How about a lookup table, or just a freakin’ array with 12 entries? What is this, amateur hour? No, the proper way of remembering the number of days in each month is some bizarre piece-wise function. It is: f(x) = 28 + (x + ⌊x8⌋) mod 2 + 2 mod x + 2 ⌊1x⌋. At least the comments are interesting.

Arduinos were sold in the 70s! Shocking, yes, but don’t worry, time travel was involved. Here’s a still from Predestination, in theatres Jan 9, rated R, hail corporate.

Last Century’s Guided Missile Steps Aside For This Guided Bullet

Here’s an image of a bullet’s path to the target. There’s a couple of things to note. First of all, this is not a tracer round, the projectile actually has an LED incorporated which was picked up as a trail in the long (relative to bullet speed) exposure. The second – and most obvious – thing to consider is the non-liner path it took to its objective. That’s because this is a laser guided bullet.

The smart bullet is a about four inches long and carries with it a light sensor, 8-bit processor, and some electromagnetic actuators. The tip is searching for a laser-painted target, with an algorithm calculating course corrections along the way and using the actuators to move fins which alter its path. For us the most interesting part is that this ammo requires a non-rifled barrel. The rifling spins the bullet as it leaves the firearm, which usually results in a straighter and more dependable path. But the microcontroller wouldn’t be able reliably steer if it were spinning.

We’d bet this ends up as a special sniper tool in video games before we hear about it on the battlefield. Check out a clip of the dart-like bullet leaving the muzzle in the clip after the break.

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DIY Air Gap Flash Saves At Least Seven Grand

Did you know that a standard camera flash is much too slow to capture high quality images of bullets? A relatively long flash duration results in blurred images of the bullet. By building this air gap flash a bullet can be frozen in mid-air, producing some stunning results. There is an element of danger here, and not from the bullet. This flash uses a 35,000 volt capacitor to produce the mini-bolt of lightning which serves as the light source. The unit can be built for a few hundred dollars, which sounds like a heck of a deal if commercial models really do start at $8k and go up from there.

Now that the photographer has a super-fast flash, a camera axe takes care of the timing… which is everything.