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Electromagnetic remote control detector

Find any remote controls, mobile phones, etc.
  [vote for,

Even if you're intelligent enough not to lose your tv remote every 5 minutes, you probably spend at least half an hour each week walking around with someone else's mobile phone calling up your own, or pondering where you've put your walkman.

Well, what all these devices have in common, apart from being portable and easily loseable, is that they're all battery-powered electronic devices, and thus I'm thinking they have to emit a certain amount of electromagnetic radiation or magnetic field even when idle. And even if that's not sufficient to pick up, a low-frequency radio transmitter or induction device could perhaps induce a characteristic signal in the electronic device.

You'd need to experiment to find the characteristic signals emitted, but I think some variation of a metal detector or tool for locating hidden wires in walls might do the job. This would give you a general purpose tool, able to find almost any electrical item you've lost, from the very small like car-key remotes to portable CD players and maybe washing machines. And *this* tool would be permanently anchored to your wall by a prominent chain or elasticated flex.

I know there's about 7 million remote-control-related ideas both on 1/2B and in the not-so-real world, so if this is (half)baked I apologise.

pottedstu, Nov 03 2001

Half-Baked Home Inventory System http://www.halfbake...0inventory_20system
Read the annotation about cheap RF tags. [BigBrother, Nov 03 2001, last modified Oct 05 2004]

Now You Can Find It http://www.sharperi...8000&pcatid=&catid=
From Sharper Image. [DrCurry, Oct 04 2004, last modified Oct 05 2004]

Nonlinear Junction Detector http://www.tscm.com/tmdenljd.html
This gadget can detect electronic devices even when they're switched off. [Wrongfellow, Oct 21 2013]


       Ought to work. The things that activate those shoplifting detectors don't seem to have batteries at all, and the detectors still pick them up.
DrBob, Nov 04 2001

       This could be a problem if theives hapened to get hold of one... still I don't supose it would make things much worse... maybe you could have a security system that shows up really brightly to deter them from stealing your nice new em emitting TV...
RobertKidney, Nov 04 2001

       You could probably do it with mobile phones, but I doubt that a {disc,walk}man would emit very much when powered down. Placing a small transmitter (a couple of watts?) would help, but you'd run the batteries down far quicker - compare the time between charges of a mobile phone to the time that a walkman can survive when switched off.   

       I'm not sure whether IR remote controls (which are the most important item in your list from my perspective) would work with this scheme without modification.   

       Also, the detector might not work in areas where there are electronic devices operating (e.g. hi-fi, computer, television) and causing 'noise'.   

       On the other hand, I'm willing to be egnored about all of the above by someone who is knowledgeable about such things. (-:
cp, Nov 04 2001

       Unless your [specify portable electronic device] has soft power control, it will not emit any type of EM when the power is off, because there is no current flowing anywhere in the circuit. Soft power controlled devices have a small circuit that is always on to detect requests for a full power-on. I have not seen soft power control in very many portable devices, though, except PDAs and cell phones.   

       As for using the technology currently in inventory control (anti-shoplifting) systems, I think we already have ideas at the 1/2B for placing locator tags on [specify any item you tend to misplace].   

I found it. See the link.
BigBrother, Nov 05 2001

       [BigBrother] Exactly. You said what I was trying to say, only you knew what you were talking about (-:
cp, Nov 05 2001

       Use a magnetic field in your ERCD to induce current in the device's circuitry. Then it will radiate EM radiation.
hippo, Nov 05 2001

       [hippo]: Yes, you can induce current in an otherwise dormant circuit. But every piece of metal in the house suddenly looks like a circuit when you do this. Now you have to filter out the TV remote from all the chaff. Good luck. RF tags use precision-cut metal strips that resonate and reflect very precise frequencies. The resonance and reflection characteristic of an electronic circuit would be too complex, too spread out, and too similar to the characteristics of innumerable oddly-shaped metal objects in the area for the locator to isolate and identify.
BigBrother, Nov 05 2001

       //Yes, you can induce current in an otherwise dormant circuit. But every piece of metal in the house suddenly looks like a circuit when you do this. Now you have to filter out the TV remote from all the chaff.//   

       Electronic devices contain nonlinear parts which cause them to emit EM radiation at harmonics of the inducing frequency, which can distinguish active devices from pieces of metal [link].
Wrongfellow, Oct 21 2013


       That brings back memories.
MaxwellBuchanan, Oct 21 2013


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