Hackszine.com: Electronics Archives

Archive: Electronics

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December 15, 2007

Using an optical mouse for robotic position sensing

The standard optical mouse contains all of the hardware necessary for tracking X/Y movement on a flat surface. With a bit of modification, you can tweak the illumination and focal length of the device to create a compact motion tracking module for your robotics projects.

Mac A. Cody has done a really nice job of documenting a couple different configurations using the common Agilent/Avago ADNS-2610 Optical Mouse Sensor that powers a lot of cheap optical mice. The motion sensor pictured above has been hacked to sit further above the surface than a stock mouse, and he's included some fairly simple example code for reading the X/Y movements from the sensor.

The cool thing about using something like this, aside from the cheap cost, is that the motion detected by this system isn't dependent on your gearing, traction, or relative speed between wheels or tracks. If you are moving, the camera detects it. If you aren't, it can tell that as well. This is pretty difficult with standard wheel encoders, where you can tell that a wheel is spinning, but not that the robot is moving.

References:
Cody's Robot Optical Motion Sensor #1 - Link
BTC Optical Mouse Hack - Link
Interface to Optical Mouse Sensor (PDF) - Link

December 4, 2007

Open source MIDI keyboard

Here's a guide for creating a MIDI keyboard from a cheapo toy keyboard.

This project details the steps to build your own Open Source (musical) keyboard which connects to a computer via USB and sends MIDI signals. This is achieved using an AN2131 development board. The AN2131 is now discontinued, so development boards can be bought cheaply on eBay. Alternatively you could use another USB microcontroller, if you are able to port the firmware. You could also hack any EZ-USB based device, of which there are many.

The walkthrough also covers interfacing your open source midi keyboard with Linux using the Bristol synth emulator. Pretty neat stuff.

How to Build an Open Source MIDI Keyboard - Link

December 3, 2007

Ardiuno-controlled Gaggia Espresso machine

Here's the latest espressotronic creation in the long human tradition of modifying machines to produce the perfect cup of coffee.

The goal of this project is to create a computer interface for my Gaggia Espresso machine replacing the factory thermal switches with a PID controller and the "steam" and "pump" toggle switches with a LCD/button menu system.
...

The machine works great! I get better stability and control than I was expecting, and it came together pretty quickly with no major problems. Additionally, I still need to finish fine-tuning the PID parameters to maximize stability.

The creator, Nash Lincoln, got a few of his ideas from a similar project which used a PIC and an NES controller to manage a Rancilio Sylvia machine. Between the two of these projects, you should have enough inspiration and technical knowhow to start hacking your way toward your own espresso nirvana.

Gaggia Espresso PID Arduino Mod - Link
Rancilio Silvia "PID PIC NES" mod - Link
PID Without a PhD - Link

November 28, 2007

Internal bluetooth hack for the Asus Eee PC

tnkgrl spent some time exploring the motherboard of her Eee PC. Looking for available USB ports, she was able to hijack the USB trace that goes to the mini PCIe slot used by the Atheros wireless card. Since the Atheros doesn't use the USB signal, the card will still function without it. This gives you a spare USB port, perfect for embedding a tiny USB Bluetooth module!

If you don't mind soldering a few traces, you can add a built-in bluetooth device to your Eee PC. You'll still have the external ports available for other devices, and your wireless card will still function. The only difference is that when you can't find a hotspot, you'll be able to get a cellphone uplink and jack in using your new bluetooth connection.

Modding the Asus 701 (Eee) - Bluetooth - Link

November 24, 2007

Turn your soundcard into an oscilloscope

There are a couple decent software packages available for using your soundcard as an oscilloscope. Using the line-in or mic-in will allow you to sample signals below 44.1kHz with 16-bit resolution (depending on your soundcard). For Linux, there's an open source GTK package called xoscope that is pretty well maintained. On the PC side, you can try a package (not open source, unfortunately) called Soundcard Oscilloscope, which was written using LabView. Both programs will allow you to instantly transform your computer into a really affordable oscilloscope. Does anyone know of a good package for OS X?

Before you go probing any circuits, keep in mind that the peak voltage on your soundcard is probably less than 1 volt. For real world use, xoscope's creator put together a buffer circuit that will take care of high voltage protection as well as a level trim that will allow you to adjust the line level to something your card can deal with. You'll want to use this with either software package you end up using.

xoscope for Linux - Link
Buffer Cicuit for xoscope - Link
Soundcard Oscilloscope for Windows 2000/XP - Link

November 22, 2007

Wiimote controlled Aibo

What works well for a gaming input device also appears to be a useful tool for human robot interaction. University of Calgary students Cheng Guo and Ehud Sharlin performed a study in which participants tried to pose Aibos and navigate them through obstacles using both keyboards and a Wiimote-based gesture interface:

For the navigation tasks we did not expect that there would be a significant difference between the numbers of errors participants made using the different techniques. However, the data showed the opposite. Participants made 43% more errors with the keypad interface than with the Wiimote interface in the navigation tasks. Many participants felt that this was due to the small key size and the unintuitive mapping between buttons and robot actions.
...

Moreover, gesture input tends to support simultaneous input
compared to button input. As one of the participants
commented, "I could do both hands (both arm movements)
at the same time without a lot of logical thinking (with the
Wiimote/Nunchuk interface), where with the keyboard I
had to press one (button) and the other (button) if I was
doing two hand movements at the same time. Although they
would be intime."

I wonder if the same holds true as the gestures become more complex to support a larger command set. For a reduced set of instructions, however, this really makes a lot of sense. Knowing the spatial position of your hands is completely second-nature, making simple gestures much more intuitive than pressing keys on a keyboard.

Wiimote controlled Aibo - Link, Paper (PDF)

November 19, 2007

Hamster-powered night light

Here's a little howto on building a low-RPM generator from scratch. I assume that not all of you have extra hamsters lying around to power your night lights, but a similar design could be used for creating a small generator for wind or other energy sources.

Though it's hard for the hamster to make higher voltages with his low-rpm wheel, he has torque to spare. 2 LEDs are barely taxing him......we are drawing only about 30 milliamps into the LEDs at Skippy's top speed. If we add more electrical load to the circuit, he could make more power, with a resulting increase in physical resistance on the wheel---like running uphill. We have yet to try small incandescent flashlight bulbs in the circuit--something that draws more power and makes more physical resistance against the wheel spinning. We did try more LEDs -- he had no trouble lighting up 6 of them. Next we plan to try an array of low-voltage incandescent flashlight bulbs to get optimum power output without tiring Skippy out too much. DanF is guessing that Skippy is good for 200 milliamps without tiring...

One cool thing is that the author uses a bicycle computer to track the hamster wheel's average and top speeds over time. This is a nice tool to have if you're trying to monitor and optimize the environment for your generator setup.

Hamster-Powered Night Light - Link

November 16, 2007

HOWTO - Fix a "Red Ring of Death" Xbox 360

The photo above is taken from a Wikipedia entry titled Xbox 360 Technical Problems, which describes a hardware failure issue that is not uncommon for Xbox 360 owners. The general problem is that the array of solder joints that attach the GPU and CPU to the motherboard can break overtime due to heat expansion during normal use. This is actually quite similar to an issue with many early model iBooks, and the fix is similar: you find a clever way to re-fuse the electronics back onto the motherboard.

Brian Whitfield wrote in about his own experience:

So ... all the Xbox 360 owners out there have one thing in common. We all dread to wake up and turn on our 360 only to find the 3 "Red Lights of Death" (RoL). That happened to me the other day, and I started to panic. Christmas time is soon, and I have absolutely no money to spend to fix up my 360. So I started looking for tutorials on how to fix this problem (as my Microsoft is off warrenty since I bought it off eBay).
I came across this lots of these "Towel Trick" tutorials. So I watched a couple videos on YouTube and read a bunch of blogs (I never knew so many people had soo much time on their hands), in any case, I figured I'd give it a shot. Now for those who don't know, the "Towel Trick" (TT) is where you turn on your Xbox 360 and then wrap it in a towel and leave it on for a certain amount of time (most tutorials say 10 mins, but I only left mine on for like a minute to a minute and a half). I turned off my Xbox and then unwrapped the towel and turned it on, and it worked. I played for a good 3 hours and no problems.

Today, I went to use my Xbox 360 and yet again, I received the 3 RoLs. So I did the same thing, and it worked again. Now most people will say this is stupid and overheating something only causes more damage to it. Well it might, but if the Xbox works, you can save yourself $140 (which is what is cost to send and have Microsoft repair it without warrenty). I can't believe something this simple worked. I was reading online somewhere (not saying this is entirely true, but hey, worth mentioning) that the reason for the 3 RoLs, is because of the solder between the GPU and the board. Supposedly, if you heat up the 360 enough, the solders melt a bit back into position. Again, not saying that is true, but good enough reason for me.

As long as my Xbox 360 works, I will probably continue to use the "TT", cause let's face it, everyone would rather have a more damaged Xbox 360 that works, then a minor damaged one that doesn't.

If the towel trick works for you, awesome. For most people, though, it sounds like it's a very temporary fix. To get the job done right, you need to liquify those solder joints and allow them to make a more solid connection.

In the case of the similar iBook issue, Mark Hoekstra from GeekTechnique was using a can of sterno atop the GPU to heat things up. That route, while demanding some sincere applause, freaks me out too much.

YouTube user twitch88 has a video showing how to use a heat gun to get the same effect. It requires a little extra equipment, but the process is a bit more controllable that an open flame. To each his own, though (and send me a pic if you are brave enough to try the sterno trick and it works).

References:
Towel Trick Info @Engadget - Link
Fix the Xbox 360 With a Heat Gun (video) - Link
Xbox 360 Technical Problems - Link
Fix an old iBook's video problems... with fire! - Link

November 14, 2007

Microcontroller design final projects from Cornell University

Bruce Land writes:

Students at Cornell University were given the responsibility of choosing, designing and building a microcontroller project,. This year's projects include laser pong, air guitar, an evolving neural robot, and a USB host controller.

During the last 5 weeks of the spring semester in ECE476, Microcontroller Design, students have to combine sensors, actuators, microcontrollers, and mathematical techniques to build something. Some projects are infrsstructure, such as an 8-bit color display for video games or a voice recognition scheme. Many groups built some kind of robot or musical device. All projects show a great deal of originality and work. There are over 200 projects on the page.

Pictured above is David Drew and Joanna Dai's autonomous neural robot, which is able to learn to navigate an enclosed space at the fastest possible speed without bumping into things. Another project, Guitar Legend Maker by Thidanun Saensuksopa and John Del Gaizo, is a real-instrument version of Guitar Hero. Instead of monkeying around with a 5 button faux guitar, you play a real instrument and the system detects the tone actually played, deciding whether or not it matches the riff that is being output.

What's really killer about all of these projects is that the are thoroughly documented, with full source, circuit diagrams, and a discussion of design decisions. If anything inspires you, you don't have to recreate the wheel to start working on your own ideas. ...And with the diversity and number of projects on the site, somthing's bound to inspire you.

Cornell University ECE 476 Microcontroller Design Final Projects - Link
Autonomous Directional Rotary Artificial Intelligence Navigational System - Link
Legend Maker, Train to Be a Guitar Legend - Link

November 12, 2007

OLPC telepresence robot

Instructables hosted an iRobot Create competition a little while ago, and one of the third place winners was Damon Kohler's OLPC Telepresence bot. It mashes two of my favorite consumer product designs into a cute mutant bot that's controllable via a web interface.

Rather than a huge electronics/robotics exercise, this project is fairly accessible to anyone with a little programming know-how. Aside from some simple wiring, the majority of the work is in the software. Damon has created a high level Python interface, called PyRobot, for controlling the Create and interfacing with the OLPC's webcam. With an afternoon of effort, you could be hacking your own little telepresence bot that you can view and control over the internet.

OLPC Telepresence Instructable - Link
PyRobot - Link
OLPC Telepresence Project Blog - Link

November 11, 2007

Lego Autopilot

Chris Anderson came up with a kid-hackable UAV, the GeoCrawler 2, using an RC aircraft and a Lego NXT:

Features: In GPS mode, unlimited pre-programmed waypoints, with programmable options such as circle and hold. Ability to integrate other sensors, such as ultrasonic, compass, gyros, accelerometers, or barometric pressure (altitude). With optional bluetooth cellphone integration, control via text message, including dynamical-changed GPS waypoints, "come home" and "circle" commands, etc.

Instructions for the GeoCrawler 2 project are available at Chris' DIY Drones site, a growing social network for folks interested in building unmanned arial vehicles.

This is really an underexplored area of amateur robotics, primarily because it's been so cost prohibitive until very recently. I'm excited to see what people come up with over the next year or two. I expect it will be mind-blowing.

GeoCrawler 2 (Lego Autopilot) Instructions - Link
DIY Drones - Link

November 10, 2007

Third Hand++: DIY improvement on the classic "helping hands"

I use the standard Radio Shack "helping hands" tool a lot when I'm working on electronics. It's pretty useful for holding components in the right place while you're soldering or working with small parts. They can be a bit of a pain, though, because the little alligator clips tend to move around, causing components or wires to wiggle out of place while you are working. There are a few positions that the arms work well in, and many configurations in which they are just not articulated enough to function well.

Instructables user rstraugh has a nice do-it-yourself solution to this problem: Third Hand++, a multi-armed, modular tool made out of adjustable coolant hoses.

I was familiar with the adjustable coolant hose systems used to spray coolant at cutting tools in the machining industry and thought that would be a great place to start. I ordered various nozzles and hose segments from my favorite online machine tool supply company and started experimenting. This is what I came up with. While it still has plenty of room for improvement it has served me well over the last 3-4 years.
These arms can be placed into pretty much any position and they will stay there.

Another nice feature is that you can make all sorts of attachments for holding whatever you need to work on. So far I've made a circuit board holder, a clamp, a mount for an LCD, and an extraction fan for keeping fumes out of your face.

The cost? About $20.

The modular attachment idea is the real killer feature here. In addition to circuitboard and probe holders, you can also make grounded or powered arms. Heck, why settle for 3 arms? I wouldn't mind a big workbench octopus.

Third Hand++: A multi-use helping hand for electronics and other delicate work - Link

October 30, 2007

Ionic wind heatsink

Inventgeek has a slick DIY heatsink project. It's completely silent, unlike the traditional CPU fan. With a $24 ion generator and a few items that you can pick up at the hardware store, the device is able to generate an ionic wind that pulls air through a traditional heatsink. The total cost is under $60, is completely silent, and puts tens of thousands of volts of static electricity an inch or two from your CPU.

The Ion Cooler 3.0 - Heat Sink - [via] Link

October 27, 2007

Accelerometer Mouse

David writes:

Bernard shows us how to use an use an accelerometer as a mouse. This project uses a MEMS X/Y accelerometer, a PIC microcontroller and a old mouse. He also describes a trick for powering the new mouse with the unused RS232 serial control lines.

This is a great idea. My optical mouse is always goofing up on my desk's wood grain and traditional ball mice, well... they suck. Word has it that Apple's next Mighty Mouse is going to be accelerometer based. Why wait when you could build your own?

Accelerometer Based Mouse - Link

October 26, 2007

FlockBots

FlockBots, created back in 2005, were the product of the Evolutionary Computation Laboratory at George Mason University. The concept was to create an open-hardware reference platform for small, sub $800 robots that could be used in education and swarm research. I was noticing this afternoon that the project's wiki doesn't seem like it's been updated in a couple of years, but the build information and pricing is still relevant. And they still remind me of a tiny Dalek army.

One thing that has changed is the available processor and motor controller technology. The original FlockBots are built around a 200MHz Gumstix board connected to an Acroname Brainstem motor controller. Peeking at the current Gumstix offerings, you can build your own FlockBot at about the same pricepoint using the 400MHz Verdex motherboard, Robostix motor controller, and a choice between a bluetooth or wifi uplink.

FlockBots Wiki - Link

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