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I want to make a project on an anti-collision system using RFID. I'm facing many problems selecting RF reader and tag: the required UHF generator, tags and reader are expensive.

Any suggestions on how to measure distance in RTL (real-time location system) using RFID?

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    \$\begingroup\$ RFID tags are not expensive, but they are short range and don't intrinsically support location. What sort of colliding things are you trying to control? You may be better off with an ultrasonic system for short distances (few meters, low speed). \$\endgroup\$ – pjc50 Dec 17 '12 at 10:46
  • \$\begingroup\$ I want to prevention anti collision between two vehicle \$\endgroup\$ – RD meena Dec 17 '12 at 12:41
  • \$\begingroup\$ I want to prevention anti collision between two vehicle .RFID is better option for high speed and long distance .if any idea about tags for distance measure (RTL system )from moving object than give me information .... thanks for comment \$\endgroup\$ – RD meena Dec 17 '12 at 12:52
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    \$\begingroup\$ Why do you say RFID is a better option? \$\endgroup\$ – pjc50 Dec 17 '12 at 12:53
  • \$\begingroup\$ i don't know more about ultrasonic system but ultrasonic system is more expansive compare to RFID system .i think ultrasonic detection range is high. if any idea about distance measure (RTL system )from moving object please give information ........ \$\endgroup\$ – RD meena Dec 17 '12 at 17:09
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RFID is a terrible method to prevent collision. Here is why:

LOCATION: RFID does not detect location. At best you would have to get multiple receivers/readers and try to do triangulation based on RF signal levels, but that is tricky and error prone.

RANGE: RFID is inherently short range. There are versions which are longer range, but these versions actually make triangulating a position more difficult.

SPEED: RFID is SLOW. The "reader" has to transmit an RF signal long enough to charge up a small cap in the tag (for the APRT version). Only then can the tag respond with its ID. The bit rate is also relatively slow. This will reduce the reaction time of your collision avoidance system.

There are versions of RFID that try to improve the range and speed, but these systems are R&D projects and not commercial products. Even if you could get one, there is no guarantee that it would work for your application.

You could try to roll your own RFID solution that would work for your application, but it is more likely that engineering a proper solution (and not trying to force RFID into this application) would give you better results.

If I were doing this project, I would be looking into those cheap radar units that are currently used in cars for collision avoidance. They are mainly used in the rear bumper to detect objects when backing up, but they are being used more and more in cars facing forward for break assist and cruise control stuff.

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