The Water Calligraphy Tricycle

September 26, 2011 by Jeremy Cook 12 Comments

Many westerners visiting or living in China may observe the art of “water calligraphy” and some may even try to imitate it. However, media artist [Nicholas Hanna] decided to take a totally new approach and make his own water painting machine.

Someone less creative would have devised some imitation of a human, but [Nicholas] decided to totally rethink the process in the form of a tricycle. Using 16 PC-controlled water solenoids, this tricycle is turned into a sort of moving dot matrix printer. It doesn’t have the same sort of grace that the traditional Chinese art does, but it’s quite a bit faster, so if you want to get your message out, this might have some practical applications.

The post doesn’t go into the electronics, but the video after the break includes some close-ups and video of [Nicholas] assembling the device. If you happen to be in china, his tricycle is part of an event for “Beijing Design Week” at the Northern Electric Relay Factory until October 3rd.

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Discrete Logic Driving Game Development

September 25, 2011 by Mike Szczys 3 Comments

[Caleb] is hard at work on a driving game based on 7400 series logic chips. This will be his entry in the Open 7400 Logic Competition, and it really outlines why this contest is especially tricky.

The concept behind the game is quite simple. You’re the driver of a car (the red dot at the bottom of the display square seen above) and need to navigate the curves in the road as you drive along. It’s the same game as we saw played on receipt paper back in June. [Caleb’s] using and LED matrix as the display, and we’re confident that if we grabbed our favorite microcontroller we could have this up and running on an 8×8 bi-color display in an afternoon. But doing it without the crutch of a programmable chip really brings out the clever engineer inside of you.

The circuit seen above is a Logisim proof-of-concept that [Caleb] went on to test on the breadboard. He thought he had everything figured out until he realized that his Data Flip-Flops were very occasionally not powering up in the same state as he predicted. Don’t worry, he found a solution to the problem. But we can’t wait to see what other hurdles he encounters as he pushes on toward completing the project.

Interfacing With A PS/2 Mouse

September 24, 2011 by Brian Benchoff 18 Comments

[David] sent in his implementation of reading a PS/2 mouse with a PIC microcontroller and some LED displays. Of course, this follows hot on the heels of using a PIC with a PS/2 keyboard so now might be the time to start digging out your old peripherals out of your junk pile.

[David] began his project trying to figure out how to connect a mouse to his breadboard. After hacking the plastic off a PS/2 mouse extension cord, he wired everything up according to the pinout. Programming the PIC to understand PS/2 commands was a little strange. [David] is used to having his microcontrollers provide the clock signal. The PS/2 protocol is a bit strange as the peripheral sets the clock. Since PS/2 is a bidirectional protocol, the mouse also accepts commands. The host – [David]’s PIC – must send the mouse a command to start sending movement data.

Because USB keyboards and mice are backwards compatible with PS/2 ports, [David] tried out a few USB mice with a USB to PS/2 adapter. Every attempt at using a USB mouse failed. Strangely, when a Bluetooth mouse was tried (via Bluetooth to USB to PS/2), everything worked perfectly. Check out [David]’s PIC mouse demo after the break.

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Interfacing With A PS/2 Keyboard

September 23, 2011 by Jeremy Cook 15 Comments

Anyone reading this post has undoubtedly used a keyboard. How they work, however, is a bit more complicated than “one button, one input.” [PyroElectro] has a great tutorial about building a PS/2 keyboard interface with a 7-segment LED display (video after the break). The tutorial also includes quite a bit of theory behind it.

The system displayed below uses a PIC controller to display the letter or number pressed. A schematic of the whole project is given here as well as a detailed bill of materials.

As for how the PS/2 keyboard works, each keystroke is encoded into a binary number or “scan code”. Most of these codes are 8-bit, but some special symbols use a longer code. Although the article doesn’t fully address it, a very similar method can be used to send data back to the keyboard for such purposes as tuning on a “capslock” or “numlock” key. Although turning on a light is fun, we could see this being used as an expedient method to control a relay for automation purposes.

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Tracking Commercial Aircraft With Salvaged Electronics

September 22, 2011 by Mike Nathan 56 Comments

ads-b_air_traffic_tracking_station

Early last year, [Edward] started work on an aircraft tracking system using components from old electronics he had sitting around the house. As you may or may not know, most modern aircraft continuously broadcast their current position over the 1090MHz band using the ADS-B protocol. [Edward] found that his old satellite receiver module was able to pick up the signals without too much trouble, and was more than happy to share how he did it.

The whole project cost him just under 5 Euros and requires the aforementioned satellite tuner as well as an ATMega48 microcontroller to decode the ADS-B messages. When the receiver is hooked up to a nice aerial and preamp he can listen in on planes within a 200km radius, but even with a simple piece of wire, he can locate aircraft up to 25 km away.

Raw ADS-B data isn’t terribly useful, so [Edward] put together a small application that plots nearby aircraft on a map for him. We imagine that it wouldn’t be too incredibly difficult to do the same sort of thing with the Google Maps API as well.

If you’re interested in putting together an aircraft tracking receiver of your own, be sure to swing by his site – he has a ton of useful information that will likely be a huge help along the way.

[Thanks, David]

Beginner Concepts: A Quartet Of Videos On Inductors

September 22, 2011 by Mike Szczys 18 Comments

Inductors can be found in many of the devices you use every day, but if you’ve been working only with DC in your projects there’s a good chance you’ve never needed to know anything about them. Now’s your chance to pick up on the basics with this video tutorial series. [Afroman] put together four short videos that we’ve embedded after the break. Set aside fifteen minutes to watch them; you’ll be glad you did.

The first in the series starts out by explaining that an inductor is a coil of wire that serves a similar function as a capacitor with one major difference. A capacitor stores voltage, while an inductor stores current. In the second video, [Afroman] hooks up some inductors to a square-wave generator, then measures the resulting current characteristics using an oscilloscope. He shows the difference between inductor core material (air core versus ferrite core) and illustrates the properties that make inductors so useful as filters. The third video covers filtering circuits, and the fourth is the best explanation of why you need a flyback diode when driving a motor (an inductive load) that we’ve seen yet.

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DIY RFID Shielded Wallet Keeps Data Thieves At Bay

September 22, 2011 by Mike Nathan 39 Comments

diy_rf_shielded_wallet

[Serge] was in search of a new wallet, but he was concerned about ne’er do wells with RFID readers stealing his data. He could have gone out to the store and plunked down $20-$30 for a shielded walled, but where’s the fun in that? Instead, he decided to make his own.

Using Kevlar-Nomex fabric, he laid out the general structure for his wallet. This ultra-strong fabric has a breaking strength of 500lbs, but blocking RF isn’t exactly its forte. To provide some electromagnetic shielding, [Serge] added a nice uniform layer of silver epoxy to the Kevlar, which carries an added bonus of strengthening the material. He fired up the sewing machine, adding a nylon strip to the exterior of the wallet for reinforcement, then he worked on forming the bill pouch and card holders.

The final result is a plain yet incredibly rugged wallet that’s sure to keep his various RFID-enabled cards safe. We really dig how unassuming the wallet is – no flash, all function. Nice job, we’ll take one!