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Archive for the ‘high speed photography’ Category

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.

This is the second such chronograph that [td0g] has built, and he changed the frame to be mostly 3D printed for easier construction, and upgraded the sensor boards to custom PCBs instead of the perfboard. If you want to build your own, all the design files are up on Github, and the light gate sensors should be for sale on Tindie soon. He has successfully used the rig to measure various projectiles ranging from 100m/s (paintball) to 875 m/s (rifle bullet). With a high power rifle, the chronograph needs to be at least 2 m from the muzzle to avoid damage or false readings from the muzzle blast, which also means the careful aim is required to put the bullet through the sensing area, without killing the chronograph in the process.

Getting the shutter to trigger at just the right moment is probably the biggest challenge of high speed photography. We’ve a number of different triggers, including for water balloon photography, and a laser for droplets.

To capture images of bullets “interacting” with various objects, photographic hacker Tyler Gerritsen created an impressive chronograph rig, able to measure the speed of a bullet launched from a rifle at 1000 meters per second. While the concept of measuring time from one sensor to another isn’t new, implementation at this speed required some interesting tricks.

To accomplish this feat, Gerritsen designed his own sensor array using photodiodes in a reverse-biased setup, and even calibrated the clock speed of the Arduino Uno for control in order to account for any variation. Finally, the time between triggering a flash and light actually appearing had to be compensated for in the code, a different value for each type of equipment.

The project write-up is a great read for anyone interested in this type of photographic or measurement technique, and the resulting photos can be seen here.

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.


Filed under: Arduino Hacks, digital cameras hacks, hardware

doubledriparticle-25High speed photography is great for capturing the moment when two water droplets collide and make incredibly beautiful fluid impacts.

Read more on MAKE

The post Capture Incredible Water Droplet Impacts with a High Speed Camera Rig appeared first on Make: DIY Projects and Ideas for Makers.

High speed photography is fun. Ultra high frame rate video, even more so. But since not many of us have access to $10,000 HFR cameras… we have to make do with long exposure shots a perfectly timed camera flash. You can design a system to trigger the flash at just the right millisecond — but they’re still pretty expensive typically.

[Electronupdate] has a 100W LED module and penchant for Arduino Nanos — so he wondered if he could make an affordable high speed camera rig — and he did.

It’s a pretty slick little setup. He has a limit switch mounted to a nail on a piece of wood — when the water balloon drops on it, it triggers the mechanical switch. The Arduino then triggers the LED flash, which is quite a large load and requires a High Side Switch to operate. A small LCD and series of buttons allow him to dial in the time offset just right in order to get some awesome photos of a water balloon exploding.

Alternatively, you can achieve the same effect with friggin’ lasers.


Filed under: Arduino Hacks, digital cameras hacks


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