Simple RFID Door Lock System

Group entry hacks are a favorite for hacker social groups. Why use old fashioned keys when you can use newfangled electronic keys? If you are looking to build a simple RFID-based security system to secure your important stuff, this project from is a good place to start. In it, [Joe Roberts] outlines the process of building a simple RFID-triggered mechanism for their office door.

It’s a pretty simple setup that is composed of an RFID reader, a Rasperry Pi and a Neopixel ring. When someone places an RFID card against the reader hidden behind a poster by their front door, the reader grabs the code and the Pi compares it with a list of authorized users. If the card is on the list, the Pi triggers the door lock using a signal line originally designed to work with an intercom system. If the user isn’t on the list, a laser is triggered that vaporizes the interloper… well, that’s perhaps in the next version, along with an API that will allow someone to open the door from the company chat application.

At the moment, this is a clean, simple build that uses only a few cheap components, but which could be the basis for a more sophisticated security system in the future.

Die Photos Of A Runner’s RFID Chip

A mass participation sporting event such as a road race presents a significant problem for its record keepers. It would be impossible to have ten thousand timekeepers hovering over stopwatches at the finish line, so how do they record each runner’s time? The answer lies in an RFID chip attached to the inside of the bib each runner wears, which is read as the runner crosses the line to ensure that their time is recorded among the hundreds of other participants.

[Ken Shirriff] got his hands on a bib from San Francisco’s “Bay to Breakers” race, and set about a teardown to lay bare its secrets.

The foil antenna pattern.
The foil antenna pattern.

Stripping away the foam covering of the RFID assembly revealed a foil antenna for the 860-960MHz UHF band with the tiny RFID chip at its centre. The antenna is interesting, it’s a rather simple wideband dipole folded over with what looks like a matching stub arrangement and an arrow device incorporated into the fold that is probably for aesthetic rather than practical purposes. He identified the chip as an Impinj Monza 4, whose data sheet contains reference designs for antennas we’d expect to deliver a better performance.

After some trial-by-fire epoxy removal the tiny chip was revealed and photographed. It’s a device of three parts, the power scavenging and analog radio section, the non-volatile memory that carries the payload, and a finite-state logic machine to do the work. This isn’t a proper processor, instead it contains only the logic required to do the one task of returning the payload.

He finishes off with a comparison photograph of the chip — which is about the size of a grain of salt — atop a 1980s 8051-series microcontroller to show both its tiny size and the density advancements achieved over those intervening decades.

Since RFID devices are becoming a ubiquitous part of everyday life it is interesting to learn more about them through teardowns like this one. The chip here is a bit different to those you’ll find in more mundane applications in that it uses a much higher frequency, we’d be interested to know the RF field strength required at the finish line to activate it. It would also be interesting to know how the system handles collisions, with many runners passing the reader at once there must be a lot of RFID chatter on the airwaves.

We’ve featured [Ken]’s work before, among many others in his reverse engineering of Clive Sinclair’s 1974 scientific calculator, and his explanation of the inner workings of the TL431 voltage reference. Though we’ve had many RFID projects on these pages, this appears to be the first teardown of one we’ve covered.

RFID Lock Keeps Your Bike Safe

What do you do with an RFID chip implanted in your body? If you are [gmendez3], you build a bike lock that responds to your chip. The prototype uses MDF to create a rear wheel immobilizer. However, [gmendez3] plans on building a version using aluminum.

For the electronics, of course, there’s an Arduino. There’s also an RC522 RFID reader. We couldn’t help but think of the Keyduino for this application. When the system is locked, the Arduino drives a servo to engage the immobilizer. To free your rear wheel, simply read your implanted chip. The Arduino then commands the servo to disengage the immobilizer. You can see the system in operation in the video below.

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GuardBunny Active RFID Protection Going Open Hardware

There are two sides to every coin. Instead of swiping or using a chip reader with your credit card, some companies offer wireless cards that you hold up to a reader for just an instant. How convenient for you and for anyone who might what to read that data for their own use. The same goes for RFID enabled passports, and the now ubiquitous keycards used for door access at businesses and hotels. I’m sure you can opt-out of one of these credit cards, but Gerald in human resources isn’t going to issue you a metal key — you’re stuck hauling around that RFID card.

It is unlikely that someone surreptitiously reading your card will unlock your secrets. The contactless credit cards and the keylock cards are actually calculating a response based on a stored key pair. But you absolutely could be tracked by the unique IDs in your cards. Are you being logged when passing by an open reader? And other devices, like public transit cards, may have more information stored on them that could be harvested. It’s not entirely paranoid to want to silence these signals when you’re not using them.

One solution is to all of this is to protect your wallet from would-be RFID pirates. At this point all I’m sure everyone is thinking of a tin-foil card case. Sure, that might work unless the malicious reader is very powerful. But there’s a much more interesting way to protect against this: active RFID scrambling with a project called GuardBunny. It’s a card that you place next to whatever you want to protect. It’s not really RFID — I’ll get that in a moment — but is activated the same way and spews erroneous bits back at any card reader. Kristin Paget has been working on GuardBunny for several years now. As of late she’s had less time for active development, but is doing a great thing by letting version 1 out into the world for others to hack on. In her talk at Shmoocon 2016 she walked through the design, demonstrated its functionality, and shared some suggestions for further improvement.

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RFID Enabled Robot Plays Music for 3 Year Old

[Ronald] has a three year old daughter who loves music, but hasn’t quite gotten the hang of complex MP3 players or the radio yet — what gives, three is pretty old?! Inspired by an RFID enabled cassette player he saw, [Ronald] decided to make her something that was cute — and easy to use.

He started with the adorable KNG Andrew Home Invader speaker, and proceeded to jam a Raspberry Pi inside. What he wanted to do was be able to put RFID tags on certain objects that his daughter could associate with her favorite music — only problem, he didn’t know how to use RFID tags! Luckily he found another article which explained how to write a script in Python in order to easily use an RFID system.

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RFID Audio Book Reader For the Visually Impaired

When [Willem] visited home last year, he stopped in at his grandparents’ house and found that his very active 93-year-old grandfather had recently gone almost completely blind and was passing the days just sitting in a chair. [Willem] suggested that he listen to audio books, but his grandfather wasn’t receptive to the idea until [Willem] convinced him that the well-narrated ones can be very gripping and entertaining. Once his grandfather was on board, [Willem] knew that he needed a much more accessible solution than a tiny device with tiny controls, so he built an RFID audio reader using a Raspberry Pi.

[Willem] has posted the build details at his personal site. Essentially, the box you see above contains a Raspi and an RFID reader. He created different ‘books’ by placing RFID cards inside of DVD boxes, which makes them more tangible and accessible. When a book is placed on the box, the RFID reader tells the Pi which mp3 files to load. The large colored buttons let the user pause, rewind 20 seconds, and control the volume.

We love to see this kind of build. It’s simple, effective, and greatly enhances the user’s quality of life. [Willem]’s grandfather loves it and uses it every day.

Quick and Dirty RFID Door Locks Clean up Nice

homemade RFID Door Locks

[Shawn] recently overhauled his access control by fitting the doors with some RFID readers. Though the building already had electronic switches in place, unlocking the doors required mashing an aging keypad or pestering someone in an adjacent office to press a button to unlock them for you. [Shawn] tapped into that system by running some wires up into the attic and connecting them to one of two control boxes, each with an ATMega328 inside. Everything functions as you would expect: presenting the right RFID card to the wall-mounted reader sends a signal to the microcontroller, which clicks an accompanying relay that drives the locks.

You may recall [Shawn’s] RFID phone tag hack from last month; the addition of the readers is the second act of the project. If you’re looking to recreate this build, you shouldn’t have any trouble sourcing the same Parallax readers or building out your own Arduino on a stick, either. Check out a quick walkthrough video after the jump.

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