High Speed Imaging Of Magnetic Fields

February 15, 2018 by Brian Benchoff 41 Comments

Some time before experimenting with MRI machines and building his own CT scanner, [Peter Jansen] wanted to visualize magnetic fields. One of his small side projects is building tricoders — pocket sensor suites that image everything — and after playing around with the magnetometer function on his Roddenberry-endorsed tool, he decided he had to have a way to visualize magnetic fields. After some work, he has the tools to do it at thousands of frames per second. It’s a video camera for magnetic fields, pushing the boundaries of both magnetic imaging technology and the definition of the word ‘camera’.

When we last looked at [Peter]’s Hall effect camera, the device worked, but it wasn’t necessarily complete. The original design used I2C I/O multiplexers for addressing each individual ‘pixel’ of the Hall effect array, limiting the ‘framerate’ of the ‘camera’ to somewhere around 30 Hz. While this would work for visualizing static magnetic fields, the more interesting magnetic fields around us are oscillating — think motors and transformers and such. A much faster magnetic camera was needed, and that’s what [Peter] set out to build.

Instead of an I/O expander, [Peter] re-engineered his design to use analog multiplexers and a binary counter to cycle through each pixel, one at a time. Basically, the new circuit uses two analog muxes for the columns and rows of the Hall effect array, a binary counter to cycle through each pixel at Megahertz speed, and a fast ADC to read each value. It is, bizarrely, the 1970s way of doing things; these are simple chips, and the controller (a Chipkit Max32) only needs to read a single analog value and clock the binary counter really fast.

With the new design, [Peter] is able to get extremely fast frame rates of about 2,000 Hz. That’s fast enough for some beautiful visualizations of spinning motors and transformers, seen in the video below. Further improvements may include three-axis magnetometers, which should allow for some spectacular visualizations similar to [Ted Yapo]’s 3D magnetic field scanner.

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Pipes, Tees, And Gears Result In Smooth Video Shots

February 13, 2018 by Dan Maloney 13 Comments

It’s depressingly easy to make bad videos, but it only takes a little care to turn that around. After ample lighting and decent audio — and not shooting in portrait — perhaps the biggest improvements come from stabilizing the camera while it’s moving. Giving your viewers motion sickness is bad form, after all, and to smooth out those beauty shots, a camera slider can be a big help.

Not all camera sliders are built alike, though, and we must admit to being baffled while first watching [Rulof Maker]’s build of a smooth, synchronized pan and slide camera rig. We just couldn’t figure out how those gears were going to be put to use, but as the video below progresses, it becomes clear that this is an adjustable pantograph rig, and that [Rulof]’s eBay gears are intended to link the two sets of pantograph arms together. The arms are formed from threaded pipe and tee fittings with bearings pressed into them, which is a pretty clever construction technique that seems highly dependent on having the good fortune to find bearings with an interference fit into the threads. But still, [Rulof] makes it work, and with a little epoxy and a fair amount of finagling, he ends up with a complex linkage that yields the desired effects. And bonus points for being able to configure the motion with small adjustments to the camera bracket pivot points.

We saw a similar pantograph slider a few months back. That one was 3D-printed and linked with timing belts, but the principles are the same and the shots from both look great.

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Plastic Model Emulates The First Untethered Spacewalk

February 11, 2018 by Donald Papp 18 Comments

Here’s something really wonderful. [Dave Akerman] wrote up the results of his attempt to use a high-altitude balloon to try to re-create a famous image of NASA’s Bruce McCandless floating freely in space with the Earth in the background. [Dave] did this in celebration of the 34th anniversary of the first untethered spacewalk, even going so far as to launch on the same day as the original event in 1984. He had excellent results, with plenty of video and images recorded by his payload.

Adhering to the actual day of the spacewalk wasn’t the only hurdle [Dave] jumped to make this happen. He tracked down an old and rare “Astronaut with MMU” (Mobile Maneuvering Unit) plastic model kit made by Revell USA and proceeded to build it and arrange for it to remain in view of the cameras. Raspberry Pi Zero Ws with cameras, LoRA hardware, action cameras, and a UBlox GPS unit all make an appearance in the balloon’s payload.

Sadly, [Bruce McCandless] passed away in late 2017, but this project is a wonderful reminder of that first untethered spacewalk. Details on the build and the payload, as well as the tracking system, are covered here on [Dave]’s blog. Videos of the launch and the inevitable balloon burst are embedded below, but more is available in the summary write-up.

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Large Format… Videography?

February 8, 2018 by Jenny List 41 Comments

Large format photography gives a special quality to the images it produces, due to the differences in depth of field and resolution between it and its more modern handheld equivalents. Projecting an image the size of a dinner plate rather than a postage stamp has a few drawbacks though when it comes to digital photography, sensor manufacturersdo not manufacture consumer products at that size.

[Zev Hoover] has created a large format digital camera, and is using it not only for still images but for video. And it’s an interesting device, for the way he’s translated a huge large-format image into a relatively small sensor in a modern SLR. He’s projecting the image from the large-format lens and bellows onto a screen made from an artist’s palette, a conveniently available piece of bright white plastic, and capturing that image with his SLR mounted beneath the large-format lens assembly. This would normally cause a perspective distortion, but to correct that he’s mounted his SLR lens at an offset.

He does point out that since less light reaches the camera there is also a change in the ISO setting on the camera, but once that has been taken into account it performs satisfactorily. The result is a camera that allows something rather unusual, for Victorian-style large-format images to come to life as video. He demonstrates it in the video below, complete with friends in suitably old-fashioned looking steampunk attire.

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Easy Time-lapse Video Via Phone And Command Line

January 13, 2018 by Donald Papp 6 Comments

A good time-lapse video can be useful visual documentation, and since [Tommy]’s phone is the best camera he owns he created two simple shell scripts to grab time-lapse images and assemble them into a video. [Tommy]’s work is just the glue between two other things: an app that turns the phone into an IP camera with a web server on the local network, and the ability to grab a still image from that server on demand.

The app he uses for his iPhone normally serves video but has an undocumented feature that allows single frames to be downloaded by adding ‘/photo’ to the end of the URL, but the ability to get a still image is a common feature on IP camera apps for smartphones. His capture script (GitHub repository here) should therefore need only minor changes to work with just about any IP camera app.

Perching a phone over a workspace and using it to create a time-lapse with a couple of shell scripts is a great example of combining simple tools to get better functionality. It could be a good way to get additional use out of an older smartphone, too. Heck, even older dumbphones can still get some use out of them; Shmoocon 2017 brought us details on rolling your own 1G network.

A Wireless Webcam Without A Cumbersome Cloud Service

December 8, 2017 by James Hobson 42 Comments

After a friend bought a nannycam that required the use of a cloud service to make the device useful, [Martin Caarels] thought to himself — as he puts it — ”I can probably do this with a Raspberry Pi!”

Altogether, [Caarels] gathered together a 4000mAh battery, a Raspberry Pi 3 with a micro SD card for storage, a Logitech c270 webcam, and the critical component to bind this project together: an elastic band. Once he had downloaded and set up Raspbian Stretch Lite on the SD card, he popped it into the Pi and connected it to the network via a cable. From there, he had to ssh into the Pi to get its IP so he could have it hop onto the WiFi.

Now that he effectively had a wireless webcam, it was time to turn it into a proper security camera.

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Rage Against The Dying Of The Light With A Raspi Night Vision Camera

November 29, 2017 by Kristina Panos 8 Comments

One of the most interesting things about hacking is the difference between the vision we have at the beginning and the reality of we’ve built at the end. What began as a simple plan to build a night vision VR headset turned into a five-month adventure for [facelessloser] that culminated in this great-looking camera. He thought it would be easy, but almost every aspect presented some kind of challenge. The important thing is that he kept at it.

One of the major issues [facelessloser] encountered was power. He found that the Pi (Zero W), the screen, and the IR LEDs draw between 1.5 and 2A altogether. He was able to solve this one by using the charging board from a 2A power bank paired with a 1200mAh Li-Po built for the high draw required by vaping. If not for space issues, he might have used a 18650 or two.

Another challenge he faced was storing the video and images. He’d considered setting up the Pi as an access point to view them from a phone browser, but ultimately extended a USB port with an OTG cable to use flash drives. With a bit of Python he can watch for the drive to mount and then write to it. If the flash drive suddenly disappears, the Pi starts saving to the SD card.

There are two videos after the break, a walk through and a night vision demo. You’ll see a bit of a lag happening in the demo video—that’s because [facelessloser] is running the feed through PyGame first. No matter what nightlife you want to peep, it might be nice to add automated zoom with a rangefinder or get a closer look with some PiNoculars.

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