Sentrifying a Nerf gun

vulcan

[Brittliv] made the mistake of getting her friends into Nerf weaponry, and so began the race to mutually secured destruction via foam darts. She may have the upper hand in this war, because her Nerf Vulcan sentry gun is both incredibly powerful and is able to be operated autonomously with a webcam featuring a friend or foe identification system.

The azimuth and elevation mount for the gun is made out of plywood, with each axis controlled by a single servo attached to an Arduino. Of course a stock Nerf gun would be fairly boring, so [BrittLiv] increased both the voltage going to the gun’s motor and the strength of the gun by replacing a 2kg spring with a 5kg spring.

Targets are tracked with a webcam using Processing and a bit of code from Project Sentry Gun. One interesting feature is a friend or foe tracking system; if the gun sees someone wearing a t-shirt with the Instructables logo, the target is identified as a friend and is not brutally mowed down with plastic darts.

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Motivating Engineering Students with Microcontrollers

We see a lot of microcontroller based hacks around here, and it’s not hard to see why learning how to use microcontrollers is valuable to prospective engineeer. Unfortunately, microcontroller courses are dreaded by students since they focus on theory instead of application. In The First Lecure, [Colin] talks to a class of engineering students about how to get practical with microcontrollers.

He starts with an overview of a bomb countdown project that he used to learn the basics of microcontrollers. This started as a 555 based timer, but he ended up using a PIC18 after having issues with timing and reliability. Next, he discusses a paintball sentry gun inspired by a Hackaday post.  He finishes off some advice and gives the students some hardware: a Pickit2 programmer and a Saleae Logic Analyzer.

It’s easy to lose motivation due to the heavy focus on theory in engineering. [Colin]‘s advice to start building stuff will hopefully motivate these students to take an interest in microcontrollers. We also like how he advises students to read Hackaday. Check out the full video of the lecture after the break.

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Detecting ASCII art across the Internet

As a web developer and designer, [Victor] has a habit of putting a very nice ASCII signature in an HTML comment at the top of every web page he designs. He was inspired by seeing others do this,  and this piqued his curiosity to see who else was doing this. His idea was to scan through a chunk of the Internet and see what other web pages had ASCII signatures in an HTML comment. With a lot of very clever work, [Victor] managed to grab some interesting ASCII art that would have been missed without looking at the source of millions of web pages.

After gathering a list of the top million top-level domains from Alexa, [Victor] wrote a script to download the HTML for all the pages in parallel. After that, it was just an issue of detecting the ASCII art in all the HTML files. There were a few earlier ASCII art detection algorithms, but nothing that suited [Victor]‘s use case. The best result came from only looking at the first comment (otherwise the signatory wouldn’t want you to find it with a quick glance at the source) that were at least 3 lines long and 40 characters wide. After discarding everything with HTML tags in it, [Victor] had an awesome gallery of the ASCII art from webpages all around the Internet.

What did he find? Well, there’s far too many ASCII signatures for [Victor] to put up on his webpage, but he did provide a nice sample of what he found. They’re mostly logos, although there is a Hypnotoad and Aperture Science sentry turret in there.

If you’d like to try out [Victor]‘s script, he made everything available on GitHub.

Portal puppet probably won’t kill us

This incredibly detailed puppet of the Wheatley from Portal was sent into us, and we a so very happy that we’re not writing about a GLaDOS build right now.

Hewn from florist foam and covered Wonderflex and Apoxie Sculpt, Wheatley pretty much tows the line as far as cosplay and prop builds go. What makes Wheatley interesting is his movement mechanism – he’s actually a hand-controlled puppet. Portal quotes come a small sound module that plays 10 Wheatley quotes. The control system has ten buttons and allows for the display of a lot more emotion than we would expect from a talking sphere. We really like the completely manual solution to an articulated robot eyeball – a really great, simple solution to a complex problem.

Like the portal turret and the adorable and friendly companion cube, we’re really impressed with the build quality of Wheatley. Yet again we’re left wondering why Valve doesn’t license some awesome toys like their office sentry.

Check out the intelligence dampening sphere in action after the break.

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A Robotic Turtle Platform to Buy or Build

This electric turtle bot instructable describes a fairly simple turtle-style robot meant to be laser cut out of acrylic (although other materials such as aluminum, MDF, or polycarbonate should work just as well). This frame is also optionally for sale, which should appeal to those that would like a mechanical robotics platform to play with, but don’t have access to machine tools. The build instructions include a detailed bill of materials which should come in handy.

As displayed in the video after the break, the robot uses a sonar sensor to navigate. This sensor is set up on a servo in order to scan the terrain, and, depending on how it’s programmed, hopefully avoid obstacles. As of when the video was taken, the little robot appears to sense an obstacle then scan with the servo left and right to see what the best way to turn is.

If this little turtle robot doesn’t have enough power for your taste, check out this autonomous ATV sentry.

Detecting muscles with electromyography

The folks at Advancer Technologies just release a muscle sensor board with a great walk through posted on Instructables describing how this board measures the flexing of muscles using electromyography.

Using the same electrode placement points as the remote controlled hand we covered earlier, the muscle is measured by sensing the voltage between the muscle and its tendon. The result is a fairly fine-grained sensing of the output – more than enough to provide some analog control for a project.

The board itself is relatively simple – an INA106 differential amp is used to sense if a muscle is flexing or not. This signal is then amplified and rectified, after which it can be connected to the analog input of your favorite microcontroller. The video demo shows the board connected to a Processing app running from an Arduino, but it wouldn’t be hard to adapt this towards remote Nerf sentry turret controlled by your biceps.

Check out the video after the break to see the muscle sensor board in action.

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Color object tracking with an 8-bit microcontroller

[Craig] sent in a link to this project which manages to implement color tracking on an 8-bit microcontroller at 60 frames per second. That’s some pretty incredible performance, but we’re also not talking about using a hobby-grade microcontroller. The C8051F360 is an ARM microcontroller with 100 MIPS throughput and with a system clock that can operate at up to 100 MHz. You also must consider that the chip will be able to do nothing else while in the tracking mode. Even with those gotchase, it’s still pretty incredible.

The setup uses an Omnivision OV7720 camera module. It has its own 24 MHz clock, which is used as the clock signal on the microcontroller’s PLL to generate a 96 MHz system clock. The code, which is written in a combination of C and assembly language, pushes captured tracking data to a PC via a serial port connection. After the break you can watch a bare-bones demo video that illustrates what the camera sees and what data shows up on the PC.

If you had the system in hand, what would you use it for? Perhaps it’s a perfect addition to that paintball sentry gun at which you’ve been hacking away?

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