When designing an RFID access control system, one has to decide what kind of reader and what kind of tags one wishes to use. They all function more or less the same way, but there are a lot of practical considerations to take into account such as cost, range, ease of use, and security options. After a lot of research, [Glen] decided on inexpensive sticker-style tags and a compatible reader supporting credentials with an ISO14443 UID that could be suitably mounted on a building’s exterior.
Breakout boards with ready-to-use code libraries exist for some RFID readers, but that wasn’t the case for the reader [Glen] had. He ended up rolling his own code to handle communication with the reader, with a Microchip PIC18F45K50 doing all the work of reading tags and performing access control. His code is on the project’s GitHub repository, and if you also find yourself needing to interface to a reader that uses the Wiegand protocol, you might want to give it a look.
Controlling the actual garage door was the easy part. All that took was soldering two wires across the switch contacts of a spare garage door opener remote, and using a relay to close the contacts. Simple and effective. You can see it in action in the short video, embedded below the break.
[Matlek] had an interesting problem. On one hand, a 40 minute bike commute without music is a dull event but in France it is illegal for any driver to wear headphones. What to do? Wanting neither to break the law nor accept the risk of blocking out surrounding sounds by wearing headphones anyway, and unwilling to create noise pollution for others with a speaker system, [Matlek] decided to improvise a custom attachment for a bike helmet that plays audio via bone conduction. We’ll admit that our first thought was a worrisome idea of sandwiching metal surface transducers between a helmet and one’s skull (and being one crash away from the helmet embedding said transducers…) but happily [Matlek]’s creation is nothing of the sort.
The bone conduction is cleverly achieved by driving small DC motors with an audio signal through a TPA2012 based audio amplifier, which is powered by a single 18650 cell. By using motors in place of speakers, and using a 3D printed enclosure to hold the motors up to a sweet spot just behind the ears, it’s possible to play music that only the wearer can hear and does not block environmental sounds.
[Matlek] didn’t just throw this together, either. This design was the result of researching bone conduction audio, gathering a variety of different components to use as transducers, testing which performed best, and testing different locations on the body. Just behind the ear was the sweet spot, with the bony area having good accessibility to a helmet-mounted solution. Amusingly, due to the contact between the motors and the rest of the hardware, the helmet itself acts as a large (but weak) speaker and faint music is audible from close range. [Matlek] plans to isolate the motors from the rest of the assembly to prevent this.
The project relies on cheap, commonly available LED strip lights. Rather than any fancy addressable strips, these are just simple strings of LEDs with current limiting resistors already fitted in a convenient, adhesive backed format. This makes the job as easy as peeling off the backing tape, sticking the strips to the helmet, and providing a power source. In clsasic entry-level hack style, everything’s running off a single 9V battery. Is it as versatile as a rechargable lithium pack with integrated controller? No, but it’s a swift way to get a project off the ground.
The trick here isn’t so much the hardware side of things – there’s nothing fancy about a battery and some LEDs. The key here is that [Patrick] identified that his children are small and difficult to see, thus it made sense to fit helmet lights rather then more typical bike lights to make them more visible to surrounding traffic.