[Pcmofo] has shared a well-built, well-explained example of how to implement an RFID key system for a door. We call this the right way because it is well thought out and functional. In the past we’ve seen doors that unlock via a secret knock, keypads, and RFID, but they are all non-permanent solutions capable being transplanted from one door to another. Rather than building a mechanism to turn the door handle, this implementation uses an electric strike mounted in the framing of the door to allow access. These are used for security doors in buildings and are built to keep your door secure.
The hack in this case is the electronics. Using an AVR ATmega168 running the Arduino boot-loader, [pcmofo] has prototyped a two-part design. An RFID reader is mounted outside the door with data wires running to the inside where the microcontroller resides. A hard-coded RFID card is used as a “master” to train any number of tags for entry. The master puts the device in training mode and the next tag to be read is added to the list of tags authorized to open the door.
We like messy wires and quickly thrown together devices but this is built to last and will look great once mounted in an appropriate enclosure.
They’ve provided a schematic for the device but we didn’t see any board artwork or pictures of the internals so you’re on your own for board layout. The libraries needed to use the bluetooth connection with homebrew software are up for download. This should provide a nice way to use the DS with a Bluetooth GPS module, or perhaps as a discrete Bluetooth sniffer and spoofer.
Do you remember the magnetic card spoofer in Terminator 2? It was a bit farfetched because apparently the device could be swiped through a reader and magically come up with working account numbers and pin numbers. We’re getting close to that kind of magic with [Jaroslaw's] card spoofer that is button-programmable.
Building off of a project that allows spoofing via an iPod and electromagnet, [Jaroslaw] wanted something that doesn’t require a computer to put together the card code. He accomplished this by interfacing a 16-button keyboard and a character LCD with an AVR ATmega168 microcontroller. Card codes can be entered with the buttons and verified on the LCD. Of course this is still dependent on you knowing the code in the first place.
As you know, credit cards use this technology. We don’t think Walmart is going to be OK with you pulling this out in the checkout line, not to mention local five-oh. This technology is also used for building access in Universities, businesses, and hotels. If used in conjunction with some other spy technology you’ll be on your way to becoming a secret-agent-man.
We’ve had a lot of requests in the comments for more Arduino centered posts so we were happy when [Njay] told us about his EDuino board. This is a minimal Arduino clone that has a crystal and its capacitors, a pull-up resistor and button on the reset pin, and a detachable serial programming connection. He also has a breadboard-friendly version seen above with all the interface pins on one side of the board. This is certainly a useful project and we’re glad to see the board files available for download. This does get us thinking… is this an Arduino, or is it an AVR ATmega168 breakoutboard that happens to use the Arduino boot loader and programming language?
Looks like they’re at it again over at Adafruit. This time they’ve produced a clock that looks more like it should be attached to a munition rather than cruising bedside. But, geek-cred aside, there’s a lot to be learned from their design. Like we’ve grown to expect, they’ve put together some good documentation on their choice of components.
Start off by taking a peek at their 5v power regulator. There is an extra diode on the output side that prevents reverse current from the 3v backup battery. The AVR ATmega168 that controls the clock is used to detect loss of power and quickly shift to the battery backup. They’ve also used the microcontroller as a boost converter for the high voltage VFD, a nice trick we’ve seen before.
We’ve seen our fair share of AVR projects, but this one’s pretty cool. AVGA is a color video game development platform based on the Atmel AVR family of microcontrollers. As seen in the picture above, one of the AVRs that the project uses is the popular ATMega168. There were several technical hurdles to using the AVRs to run color video games; one of the most difficult problems was figuring out a way to display detailed graphics from AVRs limited onboard RAM. Eventually, the developers figured out a way to display detailed graphics using a TILE-based driver. The TILE driver works by dividing the screen into X and Y coordinates, dividing the graphics into tiles. Then, when a graphic is needed it’s addressed from a reference table that’s stored in the AVR’s onboard RAM, allowing the bitmap graphic to be loaded from a game’s ROM. Currently, the only games available for the platform are a Super Mario clone, a Pacman clone, and a Snake clone. While there are only a few games available, the platform definitely looks promising. If anything, this project serves as a great example for what off the shelf microcontrollers are capable of.
The official Arduino Nano design has been updated to version 3.0. Like other new Arduino designs, it’s using the ATmega328 instead of the ATmega168. It’s also a slightly more reasonable $35. The small board is designed to be plugged directly into a breadboard and accessed via mini USB cable. This new design is also two layers instead of four making it easier to produce and modify. The new Nanos will ship at the end of the month.
[Humberto] from NerdKits sends in the newest addition to their excellent collection of videos. This video goes over the basics of DC motor control with microcontrollers. They begin by showing nine experiments and observations that can be done by the average hacker with a multimeter, motor, LED, and jumperwire. Using the results from these they show how to model and calculate the properties of a motor. Lastly, it shows how to control a motor using PWM. They have supplemental text and demonstration code for an ATmega168 on their website.
The guys over at NerdKits put together a really informative video on a meat thermometer using predictive filtering which is viewable below. The video, supplemental text, and code is available on their website. The thermometer is constructed of a LM34 temperature sensor attached to a piece of 12 gauge solid copper wire. The thermometer signal is processed on an ATmega168 microcontroller and visualized using the pygame library for python. The real gem in this project is their excellent explanation of predictive filtering, which could easily be utilized for a large number of projects.
Reader [Joe Saavedra] sent in his latest project: the spatialized umbrella. The base of each umbrella rib features an LED, speaker, and distance sensor. These are connected to an ATMega168 microcontroller running the Arduino environment. The IR sensor triggers a rain drop sound based on proximity. Shorter distances mean more droplets are played. The sounds are generated using a lookup table and the digital pins. You can see the demo video embedded below.
Using the Arduino environment without the associated board is part of another idea that [Joe] is working on. The MapDuino Project uses the standard Arduino hardware for programming, but then transfers the chip to a more barebones circuit in target project. They based their initial work on the ITP breadboard Arduino. Read the rest of this entry »
