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 I had a little fun and threw together something I always wanted to do.
Back in the day, we used these massive handsets with our land line telephones. They had just the right amount of heft and a design that allows you to ’shoulder’ the handset. You can still find them in hotels and attached to payphones.
Today our cellphones are tiny, light, and too slim to shoulder. So, with a nostalgic wisp I decided to pack a cell phone into the handset of an old rotary telephone.
Continue reading Old School Bluetooth Handset
I’m super glad I ran across this post before shelling out the money to buy and external DVD+R/RW for my netbooks. I pulled a Homer S. and asked myself why I didn’t think of this before…
 I’m not sure why I haven’t run across this in the past, but I just saw an AVR demo board called the AVR Butterfly. It has an LCD, joystick, speaker, temperature sensor, a real-time clock, voltage sensor, and serial port all for an amazing $20 over at Mouser or DigiKey. The whole package is about the size of a name tag and runs on a single button battery.
The Butterfly looks like a prime candidate for a cheap prototype platform (it has an ATmega169V Microcontroller) and diagnostic probe. Not only that, people have been using it for other projects. There’s a low power logger project called Butterfly Logger. Another project called Buttload uses a Butterfly as an ISP Programmer. So, instead of spending $22 for LadyAda’s USBtinyISP, you can give Buttload a shot since it can be modified to program over USB too.
I need to order one of these soon since I’m itching to mess with it.
Half-byte was hacked recently due to it using an old version of back-end software that was vulnerable to silly and easy security breaches.
The site should be back to its full glory shortly. I’m taking the opportunity to make changes in security as well as the overall site appearance. Stay tuned.
Update (2010/01/17): Half-byte.com should be back up and running with a new layout and theme. Most everything has been finished except a few more header images need to be created. The ones used now don’t have the best quality.
How much current does a simple over the counter five dollar laser produce when hitting a small solar panel? I wasn’t sure, so I did a little experiment.
 Using my handy multimeter, I determined the laser circuit was 4.5V at 25 mA. Since W = V * A, 4.5V x 25mA is 112.5mW. Now that’s just the internal circuit power. There’s a sticker on the the cheap-o laser explaining the laser output is < 5mW.
I had a small photovoltaic sensor from All Electronics, that has an output of about 0.5 volts. When placed under a lamp it produced 2mA of current.
 When the laser was directed on the sensor, the current registered 4.5mA. This means 0.5V x 4.5mA is 2.25mW.
The reading includes the background lamp light, so the power generated by the laser hitting the cell is much less. A lot of the light was lost due to reflection, but my objective wasn’t to test the light output of the laser. I really wanted to see how much power could be generated on the solar cell side.
 I used the Charge Station I built for a while, but the appearance started to annoy me. Why would I want to have a plastic tupperware box sitting out in my living room, especially when the duct tape was visible through the frosted top? The box was too sloppy so I made another attempt at it.
This time I spent the following (Total $7.50):
- Tiny surge protector from Daiso: $1.50
- Three wooden trays from Daiso: 3 x $1.50 = $4.50
- Hinges from Daiso: $1.50
- Elmer’s Glue: practically free…
The power adapter was cheap, so I felt free to disassemble it to fit it through the tray handle; the power plug wouldn’t fit otherwise. This was straight forward since the power adapter had regular Phillips screws.
  
I needed to use a razor to cut out the bottom of one tray to make more space for the power adapters. This was a little tedious and probably the most difficult part. But, otherwise this project was simple, fun, and quick. It only took about an hour to complete.
 There’s a good tutorial over at Instructables on making custom ethernet prongs out of zip-ties if the original snapped off. I had a busted cat5 cable causing me trouble and, surprisingly, I had the right size zip ties stowed away in my electronic gear. So, I gave it a shot.
The result ended up better than expected. The only adjustment I made was to loop some electrical tape around the prong piece to keep everything tidy and secure the prong in place.
 Who knows why the guy that designed ethernet cable heads placed the prong point towards the cable and away from the plug. They are extremely fragile and frequently snap off when you simply try to pull a cable from behind a desk or out of a nest of wires. You’d think there would be a ubiquitous design that doesn’t have this flaw.
 I’m actually tempted to snap off all the prongs on all my cables and replace them with zip-ties since this hack version correctly points the prong away from the wire making untangling much safer.
I recently thought up a great project idea that involved controlling motors from a PC. I’ve done some experimenting with an Atmel USB interface in the past, but stopped when I hit a bug in the open source toolchain. It was frustrating spending hours debugging only to find out the compiler wasn’t handing an instruction correctly.
This time I wanted to build a prototype fairly quickly and increase the budget to do so. Moving motors from a computer has been done many times before and it has been broken up into modular components. So, I only had to determine what I wanted to move and get that connected to one of many types of PC ports.
The type of motor I wanted to start with was a servo. So, I did some searching on the web and located a reasonably priced Pololu Servo controller that receives commands over an RS-232 DB9 port. Now, since most modern PC’s don’t have serial ports, I purchased a cheap USB to Serial adapter, the TU-S9. The adapter would also be useful for other projects since the serial interface is fairly basic. Since I already had a servo from Parallax, that was all I needed.
Parts:
The TU-S9 is a nice adapter since it is built with the PL-2303 chipset and is supported on most Linux distros. Once you plug it in your PC, you should see ‘/dev/ttyUSB0′ appear. This worked without problems on my Ubuntu Netbook Remix distro.
The servo controller is nice, but I initially had some problems with getting the configuration right. I started with a modified test application with a tcl UI (created for the 16 servo controller). When that didn’t work, I moved on to a Python test script. The servo’s didn’t budge with it either. The only thing that worked was a .Net test application on an old Windows PC. It was odd since running the Python script on that same PC wouldn’t work, even when the transfer signals were identical for both.
Since I didn’t have the source code for the .Net test app, I couldn’t find out what serial configuration could be different between the other applications. At one point, I simply pulled out the default DTR/RTS jumper and gave it a go. This ended up being the problem. The .Net app must have handled the RTS line properly so that it didn’t reset the controller. Wow! I wish I tested the other RS-232 lines!
In the end I was able to whip together a simple python demo script (see below) that moves the servo to various positions. Feel free to use it, I got inspiration from a previous test script.
Continue reading Servo Controller Driven over a USB-Serial Adapter
 Many companies are producing minute PC’s for different purposes. Some create them for smart home utilities, where as others create zero space thinclients. Marvell has created a cheap, pretty powerful, plug PC call the SheevaPlug. It is ARM based that can run a Linux distro and has an effective 1.2 GHz CPU with 512 MB of RAM. The compact size and minimal power draw (5V/3.0A) make this another great choice for mobile robotics. The $100 price for the development kit doesn’t hurt either.
LinuxDevices.com has a good overview of the device. More detailed specs can be found here.
Of course, there is potential for the many thinclient devices out there. They are getting more beefy and much, much smaller. The Jack PC, from Chip PC, is small enough to fit in the wall socket itself and can even be powered via LAN. The abundance of ports is useful, but the low performance, less RAM, and higher price (higher than $300) makes it less desirable. However, Chip PC did just release a Linux version of the Jack PC, which does pull some extra attention.
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I had a little fun and threw together something I always wanted to do.
