#97: Flux alarm

We are surrounded by more (magnet-containing) motorised devices than ever before. From cameras to pedal bins to door mirrors to catflaps (I haven’t mentioned these for a while, so I thought I’d grab the opportunity).

We are also increasingly reliant on magnetic storage devices, but these two technologies tend not to work well when in close proximity to each other.


Today’s invention is an alarm which is activated when a significant magnetic field moves near to your credit card or your laptop’s hard drive. It takes the form of a low-cost, stick-on patch containing a copper wire coil.

If someone happens to dump an alternator on the desk beside your patch-bearing wallet, the magnets it contains would induce a small current within the coil: enough to trigger another circuit of the type used in those annoying musical christmas cards so that an alert note sounds (or a quick burst of Silent Night, if you are doubly unfortunate).

This would be made sufficiently sensitive to the arrival of a strong magnetic field that the alarm sounds before damage can occur to the (usually less sensitive) system which is to be protected.

A variant on this patch might also be developed which reacted to high levels of magnetic flux variation; such as that which is sometimes suspected of damaging cell development in young children living near electricity transmission pylons.

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