Year: 2011

Using Your PC As A Simple Signal Generator

April 3, 2011 by 29 Comments

dc_offset_circuit

[Debraj] needed a simple signal generator for a project he was working on, but didn’t have one handy. He found that the easiest and cheapest way to get clean, reliable signaling was by using something that was already sitting on his desk – his PC.

He found that the tone generator built into Audacity was quite useful, at least for generating waveforms at less than 20 KHz or so. Upon plugging his scope into his sound card’s audio jack, he observed that the PC had good frequency fidelity, though it required an additional DC offset as most cards are built to remove that offset from the waveform.

Using a LM358 as a non-inverting summing amplifier, he was able to apply a steady DC offset and generate usable signals for his micro controller projects. A schematic for his offset circuit is available on his site, should you wish to build one of your own.

[Debraj] also notes that though Audacity is a cheap free way to generate simple signals, any number of complex signals can be generated using MATLAB if you happen to own a copy.

Hacking Game Port Peripherals To Work With Modern PCs

April 3, 2011 by 25 Comments

gameport_hack

[Atiti] has a bad habit of hanging on to old things. Some people call this sort of behavior “hoarding”, but around here we understand his affliction. It turns out that in his collection of old computer peripherals, he located a Thrustmaster Formula 1 racing wheel he used back in the day. Analog racing wheels can cost a pretty penny nowadays, depending on what you buy, so he decided to see if he could hack this outdated controller to work with his new PC.

You see, the problem with this wheel is that it utilized a “game port” connecter to interface with the computer. If you don’t remember the game port, go dig up an old PCI sound card and take a look on the back. That 15-pin connector? That’s a game port. Microsoft discontinued support for the game port once Vista was released, so [Atti] had to figure out how in the world he would get it to work on his new PC.

His solution was an Arduino, which is used to read the analog signals output by the wheel. Those signals are processed and sent to a parallel port joystick emulator, enabling him to use the wheel with any game supporting a standard joystick.

Obviously he could have just gone out to the store and bought a USB wheel, but where’s the fun in that?

Stay tuned for a video demo of his refreshed wheel in action.

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Macro Lens And Image Stacking

April 2, 2011 by 8 Comments

[Samuel Sargent] built his own lens for making stacked macro images.This project, which was completed as part of his senior thesis, utilizes a Zeiss enlarger lens. The aperture ring was broken, making it difficult to tell how much light was being let into the camera. Instead of scrapping the whole thing he turned it around, making it a macro lens when combined with a few other parts. He’s used a Nikon PB-5 belows, a PK-13 extension tube, and a body cap to provide a way to mount the lens to his camera. A hole was added to the body cap using his Dremel, and a liberal dose of epoxy putty seals all of the gaps.

After the break you can see a couple of photos that [Samuel] made of bismuth. He estimates the sharpest focal length by taking a few test shots. Next he captures a series of images, moving the bellows slightly between each shot. Finally, this set is combined using Helicon Focus image stacking software. Maybe for his graduate thesis he can build a mechanized platform to move the subject automatically.

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3D Printed Gun Fires Nerf Darts

April 2, 2011 by 24 Comments

[Vik Olliver] adds a bit more power to what has traditionally been a store-bought toy by designing this printable dart gun. His design prints the follower in the track where it belongs, which means it’s not going to come loose unless the material itself fails. After printing you’ll need to clean up that track just a bit, and ream out the pivot holes for the trigger parts. Two pieces of filament are used as the axles for pivot points and can be melted in place after assembly. A third length of filament acts as a spring, making this a completely plastic gun. Well, not completely; a couple of strong rubber bands deliver the stored energy which sends the Nerf dart on its way. The design is parametric so you can adjust it for the dart dimensions of your choosing before  printing begins.

If you still haven’t managed to boot-strap your own 3D printer don’t fret. You can always give this Nerf dart sniper rifle a try.

Robotic Berimbau Plays Itself

April 2, 2011 by 10 Comments

berimbau

If you have ever seen capoeira, you have undoubtedly heard the music of a berimbau. If you are not familiar, Capoeira is a Brazilian art form that melds martial arts, acrobatics, and music. This graceful fighting form is often accompanied by the sounds of a berimbau, a single-stringed musical instrument comprised of a gourd, a wooden bow, and a steel string.

[Ivan Monsão] and [Paulo Libonati] have constructed what is considered to be the first robotic berimbau in existence, capable of playing music without any human interaction. The robot strikes the berimbau’s metal string, mechanically muting the gourd when appropriate, and even shakes the caxixi (a rattle) in time with the music.

The builder claims that the berimbau learns songs by “listening” and repeating rather than having songs pre-programmed into the system. We can’t see any evidence of that functionality from the video, though we’d love to see the learning process in action.

While we try to find our VHS copy of “Only the Strong”, be sure to take a look at the following video of the berimbau playing itself.

[Thanks, Camilo]

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Manage Your Rechargeables At A Glance

April 2, 2011 by 17 Comments

If you enjoy photography, radio controlled vehicles, or any other activity that requires you to keep multiple sets of rechargeable batteries on hand you know how much of a pain it can be if you get a dead battery mixed in with your charged batteries. This easy approach to managing your batteries while on location does not require fancy electronics, meters or anything else that might pop into mind, but rather simple stickers and storage.

The first set of labels get stuck on the battery, offering a green and red color code along with a number so its easy to keep track of which group of batteries go where and to catalog date / life. The second set of labels gets attached to your storage compartment, when a battery is charged, place it in the box so the positive end is facing the green on the storage label, and when its dead just flip it around.

While this mainly focuses on AA batteries (and even shows you how to make a simple but effective holder out of some elastic band and staples) this idea can be used with just about any type of battery for a quick glance to see where you stand on juice.

Simple DTMF Decoder Pulls Numbers From YouTube Videos

April 2, 2011 by 28 Comments

dtmf_decoder

While many of us have banished land line telephones from our houses, there are still quite a few people who utilize POTS lines today. These analog phone systems use Dual Tone Multi Frequency (DTMF) signals in order to audibly represent all of the keys on a telephone keypad and place calls. [Brad] over at LucidScience decided that it would be useful to have a DTMF decoder on hand, and got busy building one.

His DTMF decoder box uses a CM8870 DTMF decoder chip, which you might assume is all you need to get the job done. This chip performs its duties very well, outputting a 4-bit binary code for each button press it registers, but that doesn’t do a whole lot of good without being able to represent those codes in a meaningful fashion. He first built a breadboard decoder circuit that would light 1 of 16 LEDs depending on the detected button press. This was well and good, but he decided that an Arduino-driven LCD display would work far better.

When he was finished, he had a compact decoder box with an LCD display, which accepts input from either an RJ-11 cable or an audio jack. He says that the audio jack is particularly useful for decoding tones from computer audio, such as YouTube clips. [Brad] praises the CM8870 chip, stating that it can pull phone numbers from pretty much any audio or phone signal you throw at it, regardless of quality. We think it would make a great basis for a telephone-based security system, if that was something that appealed to you.

Be sure to stick around to see his DTMF decoder circuit in action.

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