EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: whiskeyjack on November 22, 2015, 06:07:29 pm
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I am looking for a sensor which would allow non contact and non line-of-sight identification of an entity. Here is an example usage:
1) I attach the sensor module to my PC and I keep another node in my pocket. As soon as I come within one meter range of my PC, it unlocks. When I get out of one meter range, it locks back again. I also want the pocket node to send some identification information. The node that goes into my pocket can have a micro-controller and a small battery (CR2032) if at all that becomes a necessity. However I should be able to get a decent battery backup (at least a month)
2) Consider a room equipped with this sensor and various people carrying differently programmed nodes walk in. Sensor will sense the exact person and send out a greeting message. Also, the room sensor will know how many (and who exactly) are present in that room. It should also be able to know when someone leaves the room. This suggests a ping mechanism after every 5-10 seconds or so.
After some search, I found that bluetooth can be used for range measurement but I am not sure whether it will work in such a close range. Small range is a requirement. If I have flexibility to adjust range sensitivity in the range 1-5 meter, that'd be another benefit.
Second option is RFID/active RFID. Passive doesn't seem to be a good option because a tag/card is required to be brought close to the sensor. Active RFID might work but it's transmitted data can be sniffed easily and can be a security concern. Besides this, the module is quite bulky and it doesn't seem to be a suitable fit for example 1.
Is there any other option for implementing such a feature? I am not asking just for ready made solutions. If someone can suggest some ideas that I can start with, that also would be great.
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I have no clue on the technology used, but you can open some cars with the keys in your pocket...
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Second option is RFID/active RFID. Passive doesn't seem to be a good option because a tag/card is required to be brought close to the sensor. Active RFID might work but it's transmitted data can be sniffed easily and can be a security concern. Besides this, the module is quite bulky and it doesn't seem to be a suitable fit for example 1.
The range of the passive RFID pretty much depends on the shape and the size of the reading antenna and the radiated power from it. That most require close contact doesn't mean it is necessary - I have seen a project where a yagi antenna was attached to a gun-like device and used to read RFID-enabled passports and credit cards from many meters away.
There are also large RFID readers meant to be used with vehicle and asset tracking - those work up to a few meters as well.