AVR RFID, Optimized and Ported to C

Way back in 2008, I posted a writeup about using an AVR microcontroller as an RFID tag. Since then, it’s been great to see many people pick up this code and build their own DIY RFID tags. In my original project, I was just interested in using an AVR as a way of emulating any tag protocol I wanted, even proprietary protocols like the HID cards that are so common for door entry. But a general purpose microcontroller really lends itself to making... Read More

AVRFID 1.1 Firmware

I don’t normally write bloggy posts on every version of every source file I check in, but every so often an older project sees some more activity, and I love the opportunity to revisit software I wrote years ago. Sometimes I wonder why I wrote such-and-such thing that way and oh my god what an ugly hack. But usually it’s just refreshing to think about a problem I haven’t thought about in a while. The AVRFID was a quick but rather... Read More

Open source extra-sensitive high resolution TED receiver

Previously on the bloggy blog, I posted a few of my projects related to home data acquisition and to The Energy Detective (TED), a whole-house power measurement device. I made a set of homebrew wireless temperature sensors that display graphs on a digital picture frame, I reverse engineered the TED protocol, built a small self-contained open source TED receiver, and used that design to make a nifty clock. So, I wanted to take the next step and set... Read More

Lego Sky

Over the weekend, I had a chance to finish up a project that I started (and immediately became distracted from) several weeks ago. In our house, Paul and I have a game room. This is where the video games live, as well as other assorted geekery. We have Magic cards, D&D books, some manga.. it’s super nerdy Best of all, Paul has a Lego city on display. We had been looking for an interesting way to add light to the city, so when I saw some... Read More

Self-contained TED receiver

My previous entry introduced a homebrew receiver for the powerline-based data protocol used by The Energy Detective. I just designed a second revision of that receiver. This one is self-contained: It gets power and modulated data from a 9V AC wall-wart transformer, and decoded data leaves via an RS-232 serial port at 9600 baud. Best of all the circuit is very simple: Just an 8-pin microcontroller and a single op-amp. Major changes in this version: DC... Read More

Interfacing with The Energy Detective

I recently bought The Energy Detective (TED), a pretty inexpensive and friendly way to keep tabs on your whole house’s electricity usage. It’s a lot like having a more featureful version of your utility company’s power meter, sitting on your kitchen counter. It can estimate your utility bill, and tell you how much electricity and money you’re using in real-time. The resolution is pretty good- 10 watts, 1 second. As a product,... Read More

Using an AVR as an RFID tag

Experiments in RFID, continued… Last time, I posted an ultra-simple “from scratch” RFID reader, which uses no application-specific components: just a Propeller microcontroller and a few passive components. This time, I tried the opposite: building an RFID tag using no application-specific parts. Well, my solution is full of dirty tricks, but the results aren’t half bad. I used an Atmel AVR microcontroller (the ATtiny85) and... Read More

R/C helicopter lights, Revision A.5

Atmel is going to personally revoke my electrical engineering license if they ever find out what’s in that yellow heat-shrink blob, but I now have a shiny new 5 gram version of my helicopter light kit =D This version has all the same remote-control dimming and strobe capabilities of the heavier Revision A. The only practical drawback is that it isn’t quite as bright.  Read More

Hardware sketch: R/C helicopter light kit

As great as it is to finish a professional-looking hardware project with optimum component choices and full design documentation, I love the feeling of sketching in hardware (or as I’ve called it in the past, improvisational electrical engineering). Despite all the faults and rough edges in today’s development tools, we do live in a world now where it’s easy turn an idea into a working prototype with very little time and money. Flying... Read More