Raspberry Pi As Speed Camera

Wherever you stand on the topics of road safety and vehicle speed limits it’s probably fair to say that speed cameras are not a universally popular sight on our roads. If you want a heated argument in the pub, throw that one into the mix.

But what if you live in a suburban street used as a so-called “rat run” through route, with drivers regularly flouting the speed limit by a significant margin. Suddenly the issue becomes one of personal safety, and all those arguments from the pub mean very little.

Sample car speed measurements
Sample car speed measurements

[Gregtinkers]’ brother-in-law posted a message on Facebook outlining just that problem, and sadly the local police department lacked the resources to enforce the limit. This set [Gregtinkers] on a path to document the scale of the problem and lend justification to police action, which led him to use OpenCV and the Raspberry Pi camera to make his own speed camera.

The theory of operation is straightforward, the software tracks moving objects along the road in the camera’s field of view, times their traversal, and calculates the resulting speed. The area of the image containing the road is defined by a bounding box, to stop spurious readings from birds or neighbours straying into view.

He provides installation and dependency instructions and a run-down of the software’s operation in his blog post, and the software itself is available on his GitHub account.

We’ve had a lot of OpenCV-based projects but haven’t featured a speed camera before here on Hackaday. But we have had a couple of dubious countermeasures, like that humorous attempt at an SQL injection attack, or a flash-based countermeasure.

Add A Slide Show To Your Fish Tank

Once in a way we get a hack that makes us wonder – why didn’t we think of that ? [hydronics] tore apart an old LCD monitor and built a fish tank around it. Not sure if the fish notice that they are swimming on the Moon, but it sure makes for an interesting fish tank display.

He starts by ripping apart an old 19″ LCD monitor and built an acrylic fish tank around the display. The backlight of the panel is fixed at the rear side of the fish tank, along with the rest of the electronics from the old monitor.

For an earlier version, he built his own back light, but the second version with the original back light turned out much better. The fish tank pieces were joined together using acrylic glue and left over night to dry, although he still needed to use some silicone to plug leaks.

A Raspberry Pi connected to the monitor’s HDMI input provides the background slide show. [Tony Rieker] helped add bubble animations via some OpenCV code running on the Pi. A live feed of the fish is overlaid on the slide show, adding a level of inception to this tricked up fish tank. The project was recently shown off at the Portland Winter Light Festival.

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Measuring Capacitance Against Voltage

Ceramic capacitors are pretty much the pixie dust of the electronics world. If you sprinkle enough of them on a circuit, everything will work. These ceramic capacitors aren’t the newest and latest technology, though: you can find them in radios from the 1930s, and they have one annoying property: their capacitance changes in relation to voltage.

This is a problem if you’re relying on ceramic caps in an RC filter or a power supply. What you need is a device that will graph capacitance against voltage, and [limpkin] is here to show you how to do it.

Of course capacitance is usually measured by timing how long it takes to charge and discharge a cap through an RC oscillator. This requires at least one known value – in this case a 0.1% resistor – by measuring the time it takes for this circuit to oscillate, an unknown capacitance can be calculated.

That’s all well and good, but how do you measure capacitance against a bias voltage? EDN comes to save the day with a simple circuit built around an op-amp. This op-amp is just a comparator, with the rest of the circuit providing a voltage directly proportional to the percentage of charge in the capacitor.

This little project is something [limpkin] has turned into a Kickstarter, and it’s something we’ve seen before. That said, measuring capacitance against a voltage isn’t something any ‘ol meter can do, and we’re glad [limpkin] could put together an easy to use tool that measures this phenomenon.

Texel: Art Tracks You, Tracks Time

French robot-artist [Lyes Hammadouche]  tipped us off to one of his latest works: a collaboration with [Ianis Lallemand] called Texel. A “texel” is apparently a time-pixel, and the piece consists of eight servo-controlled hourglasses that can tip themselves over in response to viewers walking in front of them. Besides making graceful wavelike patterns when people walk by, they also roughly record the amount of time that people have spent looking at the piece — the hourglasses sit straight up when nobody’s around, resulting in a discrete spatial representation of people’s attentions to the piece: texels.

We get jealous when we see artists playing around with toys like these. Texel uses LIDAR scanners, Kalman-filtered naturally, to track the viewers. openFrameworks, OpenCV, and ROS. In short, everything you’d need to build a complex, human-interactive piece like this using completely open-source tools from beginning to end. Respect!

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Creating Video Trails In OpenCV

The video trail effect is nothing new: it was first used in music videos like “Blame it on the boogie” from the Jackson 5 in 1978. Now,  [Antonio Ospite] has put together a nice article that shows the basics of using OpenCV to create this effect in live video. He used the open source video processing package OpenCV for this, creating the effect with a short script. It can run in multiple ways, creating video trail effects, or “catch-up”trails (where the trail reverses into a final frame).

This provides an interesting example of how these video effects have become so much easier to create. The Jackson 5 video was created using a Scanimate and Quantel Paintbox system that was as big as a closet and cost hundreds of thousands of dollars. Now, you can create these effects with free software and a cheap PC. Now you just need to figure out what in our modern world looks awesome with this throwback effect.

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Getting Biometrics in Hand

It is amazing how quickly you get used to a car that starts as long as you have the key somewhere on your person. When you switch vehicles, it becomes a nuisance to fish the key out and insert it into the ignition. Biometrics aims to make it even easier. Why carry around a key (or an access card), if a computer can uniquely identify you?

[Alexis Ospitia] wanted to experiment with vein matching biometrics and had good results with a Raspberry Pi, a web cam, and a custom IR illumination system. Apparently, hemoglobin is a good IR reflector and the pattern of veins in your hand is as unique as other biometrics (like fingerprints, ear prints, and retina vein patterns). [Alexis’] post is in Spanish, but Google Translate does a fine job as soon as you realize that it thinks “fingerprint” is “footprint.” The software uses OpenCV, but we’ve seen the same thing done in MATLAB (see the video below).

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Hackaday Prize Semifinalist: Picking Up Litter With Robots

On beaches, in parks, and in [BDM]’s back yard, there’s a lot of liter everywhere. The normal solution to this problem is to hire someone or find some volunteers to pick up all this trash. We’re living in the future, though, and that means robots. For his Hackaday Prize entry, [BDM] is building a robot that picks up trash.

A robot that picks up litter is a very, very interesting problem. It can’t be controlled by a person, or else it would be more efficient to just get out there and kill your back picking up bottles. This means it must work autonomously, and that means identifying litter, picking it up, and disposing of it.

For the identification part of the problem, [BDM] is using computer vision that captures an RGB image and discriminates against natural objects. Right now the computer vision is far from perfect, but it does a very good job, all things considering.

The next biggest problem is picking the trash up and disposing of it. For this, [BDM] has repurposed a Power Wheels and attached a DIY robot arm. It’s not a very powerful arm, and a children’s toy probably isn’t the best platform, but it is the start of something very, very cool.

You can check out [BDM]’s video for the project below.

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