September 5, 2013 /
This build uses good old FSK (frequency shift keyring) technology sending 1′s and 0′s through the air. Although its applied using infra-red, the same concept is used for RF. Also Infra-red is still technically wireless (lol). So on to the build. Just in-case you want to brush up on your FSK I recommend just straight up hitting wikipedia. (If not, here’s the TLDR version; A steady pulse is used to represent a 1, and a variation in the pulse width is used to represent a 0)
On the transmitter side a 555 timer is set up as a Astable Multivibrator, the digital input (fed from say a microcontroller) pulls down the transistor which modifies the frequency of the 555 timer, causing a 0. Leaving the pin high (representing a 1) leaves the 555 timer alone. The data is transmitted via infra-red led.
On the receiver side, a 565 PLL (Phase Lock Loop) IC locks on to the frequency of the 555 timer and outputs a 1 or a 0 when the signal alternates between the 2 frequencies.
This is a great project but mostly as an educational one. Full post up on gadgetronicx.
August 31, 2013 /
The weekends are a good time to learn something new. I stumbled on this site called Learn X in Y Minutes. It’s a crash course in a decent sized list of programming languages and tools. There aren’t any chapters or anything, it’s like viewing the source code of a language to learn it.
I wouldn’t recommend the site if you don’t know any programming languages however, but if you know … C, you can check out ruby or haskell and I’m sure from just the code and comments you’ll pick a few things up. While it’s mostly programming, there is shell scripting with bash, and git. And once you learn git, you can add your own to the list!
August 29, 2013 /
Ever pick up a transistor without being able to read the part number to look up ? Or can’t find it when you look it up ? Well grab a multimeter and with a little know-how you might be able to figure it out.
First thing is to find the base, this can be done by measuring the resistance. Once you have the base figured out, then with the tip of your finger touching the base (acting like a switch) you can determine which one is the collector, and which one is the emitter. Sounds cool right ?
Check out the full instructions here. (fixed link)
August 21, 2013 /
You’ve learned how to use your local hackerspaces’ laser cutter and cutting acrylic like crazy but you want to start getting into some wood projects. Well one favorite among the DIY community is using Baltic Birch. It’s a plywood, so it’s strong but also available in real thin increments.
Dan was nice enough to create a post describing some of the details of Baltic Birch. Apparently you can tell the number of ply’s by the thickness, also what kind of grading scale is “CP” ? If you’re trying to buy wood off the internet for your laser cut box you may want to stick to grade “B” because seeing those patches will look ugly when stained. Or you may be OK with a lower grade wood when building a structural piece.
Whatever your reason, you should read the post if you intend to work with this medium.
August 15, 2013 /
Albeit slowly, git is taking over your crusty old subversion repository. The mainline Linux kernel development has already switched and github is just about as popular as ever nowadays! So it’s time to learn some git commands.
Git might be a little difficult to wrap your head around at first, especially if you are used to using svn now. Some things don’t translate 1:1. I found this great resource called Git Magic . It’s a GPL’d book on git. It’s available in a ton of different formats and languages. I prefer the PDF version myself. It starts out by helping you get the concept around git, when you clone a repo (… check it out in svn speak) you are creating your own repo, which you publish your changes, and eventually push the changes upstream. Then it covers a few scenarios that you are likely to run into. A great book on git, especially for the price. Well worth a read.
If you’re too lazy to read there’s always a cheat sheet.
August 14, 2013 /
Unless you’re just upgrading from windows 3.1, you’ve seen the cheap SDR (software defined radio) rtl-sdr project. SDR’s aren’t new but someone figured out how to turn a cheap sub-20$ dongle into a decent SDR bringing the entry price low enough for everyone to experiment with them.
Every electronic device you own is screaming its name into the infinite void
Melissa Elliott has put together a presentation titled “exploring the world of unintentional radio emissions” that was presented at DEF CON. After talking about the concept itself, she shows you how almost everything that runs on electricity emits some sort of electronic signature. That signature can be profiled and sometimes data can be decoded from it.
No it’s not time to break out the tin foil hats or anything but if you really are paranoid, Melissa gives some tips how to shield this information in the form of Faraday cages. You don’t have to be an old ham radio buff or even a budding electronics engineer to appreciate how cool SDR’s are.