[Noisebridge-discuss] Please Return Dremels & Philips Screwdrivers
Garrett Mace
garrettmace at gmail.com
Wed Jan 16 01:09:39 UTC 2013
On 1/15/2013 10:14 AM, Garrett Mace wrote:
>
> --- Garrett
>
> On Jan 15, 2013, at 8:49 AM, jim <jim at systemateka.com> wrote:
>
>> Can you point us to plans and parts for making
>> a useful detector?
>>
>>
>>
>>
>> On Tue, 2013-01-15 at 10:03 -0600, Martin Bogomolni wrote:
>>> Actually .. that's not a terrible idea. The stickers that are used
>>> are not trackable in anything other than the "something is passing the
>>> portal" sense, and it's a fun project to make the detector. I have a
>>> spool of five hundred of those stickers I was using for a project a
>>> few years ago.
>>> _______________________________________________
>>>
Sorry, tried to respond from my phone and fumbled the ball.
Not sure which type Martin has. The most common type use a resonant
magnetizable material that is tuned to a 58kHz mechanical vibration. A
58kHz pulsed magnetic field will make the tag resonate, and it will
continue to resonate for a while when the pulse ends. This will induce a
continuing magnetic field. The detector can filter for a 58kHz field
when the transmitter is off, and if you're being a little more elegant
will also make sure the phase matches the transmitted signal.
The tags are small enough to stick on most tools, but susceptible to
accidental damage or identification and removal by people who have been
around the block a few times on this whole stealing activity. Most power
tools, test equipment, and computing devices probably contain enough
empty space inside to locate a tag (away from the motor), and it would
work for socket set and drill bit cases. Screwdrivers and wrenches would
be more difficult.
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