| Electronics > Projects, Designs, and Technical Stuff |
| Sensing an RFID car key? |
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| iXod:
Is there an electronic way to locate a lost car key? It’s a 2004-vintage transponder key which uses the immobilizer system (315 MHz?) I can get to within 12” (30 cm) of where I suspect the key is. I have a spare key to experiment with if necessary. No need to communicate (challenge/response) with the key—indeed this is beyond my skills. A new key and programming is more than US$200 so I’m motivated to try something geeky... Thanks.. |
| Yansi:
Immobiliser is 125kHz. And I strongly doubt you can locate it very far, especially using simple equipment. If you are just a foot away from where it is, then just stick there a hand and take it out. Not sure what kind of localisation would you help with searching a cubic foot. |
| iXod:
I can get to within 12”—along 1000 feet (330 m) surface—of the area I need to search. Let’s stick to the viability of electronic means to search. Thanks. |
| Yansi:
Okay understood then! Just get/build yourself a GDO (resonance dip meter for 125kHz). It should be possible to detect the 125kHz resonant circuit in the RFID transponder even at such distance, if the meter will be sensitive enough. (Which you can of course test and improve before searching it ib the wild) I hope you don't have it inside sone metal tube or sorts. That would not work. |
| mikeselectricstuff:
I'm not familiar with the specific protocols used in keyfob transponders, but in some cases all you need to do is create a 125kHz field and look for any modulation in the loading of it - a simple diode detector can do this. For 12" range you'd want an antenna of similar diameter. A possible issue is that the antennas in keys are rather directional, so you will either need to try the antenna in different orientations, or use multiple antennas with different orientations. |
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