NFC "force" activation

[TefaTBob]

Hi all, forum n00b here. Firstly, I apologize if this weirds anyone out, but I have an NFC tag (made by Dangerous Things) implanted in my right hand. That being said, I was wondering if anyone could imagine how to go about, and if it would be even possible, to wire the kill switch/main switch with a NFC antenna (possible combined with an arduino controller) so that the saber was "force" activated and only I could actually turn it on, kind of like mentioned in the EU.

[Forgetful Jedi Knight]

Welcome to the Forums.

While a Crystal Focus card can allow for "motion activation", there is no current way of making it turn on remotely, only by you. You'll have to use a saber like the rest of us for now. ;) A "Kill switch" (known here as a "kill key") is meant to completely cut the power from the battery to the sound card while not in use.

[Askew Wai]

Hi there TefaTBob,

The NFC tag appears to be passive, so using it as a switch will require swiping it close to a receiver inside your hilt. If it is in the webbing of your thumb you would have to build around not having the device switching at the wrong time. It sounds like it could be done, but as FJK notes above, it won't be a traditional kill key cutting off power. Power would still need to be delivered to the receiver. Managing power for the receiver and for the LED will be something to be wary of. Maybe even separate batteries. The website you linked did have some interesting information, but not specifically how to build your device. I imagine it is possible, the components look small (although I did not see exact dimensions). Alternatively you could wave a magnet over a reed switch (but any magnet would do) or install a key fob receiver (secure, encoded to "just you") for similar effect. I'm exploring those latter options but it is definitely beyond my electronics know-how today. Maybe tomorrow. Good luck, let us know what you learn!

[MedicineMan]

Have you looked into capacitive touch sensors? I've thought about doing a saber using one.

[Bandit_Grey]

I was mulling this over in my head... and I don't think you could do it as a traditional kill switch per say... however you could wire something up that keeps power from the board unless the RFID tag was in place.

The circuit would need to include a constantly powered microcontroller with the RFID receiver and an NPN transistor. That transistor would control the power going to the sound board. So, you could forego a kill key entirely and have a constantly powered microcontroller such as a PIC or ATMega listening for your RFID tag. When it receives the RFID signal, the NPN transistor would allow power from your main battery pack to flow to the saber's sound board.

Additionally, if you didn't want to use two power sources you could simply split the power from your main power pack through enough resistance so that you power your microcontroller within its ratings. You can easily do this with an Arduino mini, however ATMega's are easy enough to work with that you could save some money and build one from scratch with a ATMEGA328, 16ghz crystal, and a few 10pf caps.

I can provide a diagram for you if you would like =)