Experimenting With An Air Muscle And Sensor Feedback

November 21, 2011 by Mike Szczys 29 Comments

Check out this setup that [Ruenahcmohr] is using in his air muscle experiments. The orange mesh contains an air bladder that is connected to a hose on the right side. The bladder can be filled, or emptied with two solenoid valves not seen here (but you can get a good look in the video after the break). The muscle attached to chain on the other end and is kept under constant tension by a spring. The chain bends 180 degrees around a gear which is connected to a potentiometer. This gives feedback to the ATmega32 which controlling the whole thing. This way, the slider seen above can be used to control the apparatus.

We don’t know if [Ruenahcmohr] has a use in mind for this setup, but it certainly looks promising! We’ve seen these air muscles used for haptic feedback before, but right now we’re drawing a blank when it comes to ideas. What would you use it for?

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Getting Useful Data From A Dirt Cheap RFID Reader

November 19, 2011 by Mike Nathan 21 Comments

cheap-rfid-reader

[Aaron] was looking for a cheap RFID reader that had some easy to follow documentation and a standardized interface. Most everything he saw was pretty expensive, so he decided to buy a cheap $10 reader from eBay to see how easy it would be to work with.

The reader came with very little documentation, but [Aaron] did know that the device identifies itself as a USB keyboard, outputting scan tag data into a text editor. That functionality wasn’t incredibly useful, so he took it apart to see if he could interface with it in some other manner. Exposing the PCB revealed an unknown IC for which he could find no documentation, but the board did include some breakout pins, so [Aaron] started by probing those for data.

He tried reading the data in both a terminal program and with a logic analyzer, but nothing seemed to make a whole lot of sense. He turned the sampling rate of the sniffer down, and things started looking a little better. After comparing the data from the sniffer with known tag codes, he noticed that each digit had an offset of 39 applied, so he whipped up a bit of code to correct the numbers.

[Aaron] did a good amount of legwork to get usable data from the reader, but at a cost of $10 it can’t be beat. We certainly know what we’re going to be hunting for on eBay this afternoon…

Lighting LEDs With Raindrops

November 18, 2011 by Mike Nathan 40 Comments

[Steven] had one of those musical gift cards laying around, and thought he might as well reuse the piezo speaker inside it. Without a particular project in mind, he soldered an LED to the piezo and tapped on it, which caused the LED to illuminate as expected. He started to wonder what quantity of force would be required to light the LED, and if it could be done by a raindrop.

He first tested his theory in the shower, and as you can see in the video below it actually worked, though the light was dim and sporadic as you might imagine. He eventually discovered that for optimal lighting, the piezo worked best when struck by single droplets falling with pauses in between, from a minimum height of 4 feet. To achieve a water flow within those specifications, he built a rain funnel so that he can control the droplet frequency and intensity.

It seems to work pretty well from what we can see. Off the top of our heads we can’t seem to come up with any practical applications of the water powered LED, but it is an interesting set of experiments nonetheless.

Have an idea to use this setup that we totally missed? Let us know in the comments!

[Thanks, Rob]

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A Head-mounted Tesla Coil – What Could Possibly Go Wrong?

November 18, 2011 by Mike Nathan 26 Comments

We can hear the commercial now…

“Reeeeeeal men of geniuuuuuuus! Here’s to you Mr. no-fear, singing Tesla coil on your hat wearing guy…”

Call him a genius or call him crazy – all we know is that [Tyler’s] Tesla coil hat is awesome! Even though it’s the middle of November, we couldn’t pass up this Halloween costume.

[Tyler’s] creation essentially boiled down to taking a standard dual resonant solid state Tesla coil and shrinking it down to a reasonable size for mounting on his skull. The mini Tesla features a pretty compact boost core which worked reasonably well, at least for a little while. He says that the boost never truly worked properly and needs a redesign, which is something he’ll tackle when he gets some free time.

Boost issues or not, we think that the video below speaks for itself. The hat is certainly an attention getter, and we think it’s great – even if wearing a Tesla coil on your head is not necessarily the safest thing to do.

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This Animatronic Horus Guard Mask Is So Good, Even Anubis Would Be Fooled

November 17, 2011 by Mike Nathan 32 Comments

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[Jerome Kelty] is a big fan of the movie Stargate, and when he saw it for the first time, he wanted one of the awesome helmets worn by the Horus Guards. This isn’t the kind of thing you would normally find at your local costume shop, so he knew that he would have to build one of his own. After rejecting multiple designs over the years, he finally came up with a solution that he thought would work well.

His Horus Guard helmet was constructed primarily out of cardstock, papier-mâché, spray foam, and spackle. Don’t let that list of materials give you the wrong idea about this helmet however – it looks absolutely amazing!

Not only does it look good, but it moves just like the guard’s helmets in the movie too. To control the helmet’s movements [Jerome] used an Arduino animatronics setup he designed, which we’ve seen before in his slick Predator build from last year. The Arduino controls a set of 5 servos, which are tasked with turning the helmet’s head and actuating the fans mounted on either side.

Stick around to see a short video of the mask in action, and if you’re thinking of building one yourself, be sure to check out his writeup for a very thorough BoM.

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20 Kilovolts Replaces Push Pins On This Bulletin Board

November 10, 2011 by Mike Szczys 89 Comments

Electrical Engineers don’t need push pins. That’s because they know how to control electrons! [Sven] put his knowledge of these subatomic particles to use when building his high voltage bulletin board. It uses a set of vertically strung wires to keep paper pinned against the board. The wires have high voltage at low current travelling through them. They’re in front of the board, but not touching it, and the board is serving as a ground plane. In this way an electrostatic charge pushes (or should that be pulls?) against the paper to keep each sheet right where he places it.

In the video after the break [Sven] gives us a tour of the hardware at work here. It starts with a 12V psu which feeds a buck converter. The regulated feed is patched into a high voltage supply which was designed as a CCFL driver. Finally, a voltage doubler is used to reach the final voltage, measuring about 20 kV per wire.

Don’t worry, [Sven] says the bare wire is “almost completely safe” because of the low current being conducted.

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Bullhorn Mod Lets You Disperse Angry Crowds To The Dulcet Tones Of [Kenny G]

November 10, 2011 by Mike Nathan 11 Comments

megaphone-mod-aux-audio-in

[Randy] had a cheap megaphone, and like most models in this price range, it didn’t have an audio input jack on board. He wanted the ability to pipe both music and audio from an external mic through the megaphone, and in a brief tutorial, he shows how he modified his bullhorn to do just that.

Most megaphones carry their electronics near the built-in mic, just outside the battery compartment. Removing the screws from the cap in [Randy’s] model revealed a circuit board and a couple of wires connecting it to the on board mic. His megaphone happened to play some canned music from a secondary circuit board, and he spliced in an audio jack with a built in cutoff switch between that and the main PCB. He also added a resistor in between his jack and the microphone circuitry to attenuate the line level signal properly. Once he reassembled everything, and then tested his input using a portable audio player, slowly ramping up the volume to the desired level.

It’s not every day that you require the ability to blast music through a bullhorn, but [Randy’s] modification is a great addition when you do need it.