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need help in RFID circuit


New Member
I have decided to use RFID technology to locate products or small items in home. I was wondering that can I able to build RFID reader and a transponder. If anyone knows about it..plz help me..I need the circuit for RFID receiver and transponder and any useful information regarding RFID. I thought i would use PIC controller to find out the distance b/w the product and the reader. U can email me to gaurav707@hotmail.com..thanx guys..


New Member
what kind of distances are you talking about? inches? feet? meters? multiple meters? it makes a huge difference.


New Member
gaurav707 said:
i m talking abt feet..ard 10-20 feet..For this purpose, is it better to use RF technology or RFID?
20feet ..so ur looking on to active rfid system, where both transmits.
... to find out the distance b/w the product and the reader
i don't think that an easy task .:rolleyes:


Well-Known Member
Most Helpful Member
Microchip have a few application notes showing how to design RFID circuits.

Have a look at this RFID Application Note. It even has a schematic on page 107 (Adobe counting) using a 16C84 !!

As AKG said, above a few inches distance will be tricky.

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New Member
hey..i cant open the link...can u try to email it to me if possible..gaurav707@hotmail.com...or any other way to access that website..


New Member
this doesn't sound like a task for RFID, which, as the name implies, is for identification, not for measuring distances or location...

do you actually need to identify the objects with unique ID's, or are you only concerned with the distance measurement?

Either way, if you want 10+ feet, you need to be using an active tag, and probably one that's actively transmitting RF instead of backscattering, at which point it's really just a small radio transmitter, with a microcontroller if you need the ID functionality, and not really a traditional RFID system at all. If you build a small transmitter like that, then you can try to measure the signal strength at the receiver to get an idea of distance... search for RSSI (Received Signal Strength Indication)

But I have to warn you, don't expect it to be an easy project. I had a friend attempt an RSSI-type radio transmitter location project for his senior project as a EE student and ended up having to give up and switch to IR to get it done on time.
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New Member
I don't think signal strength is going to be sufficient as antennas are not perfectly uniform point sources - orrientation will matter. Of course, you could use accelerometers in the mobile unit and broadcast orrientation, too. getting kind of complex, though.

frankly the more I think about this more it sounds like a dead-end.

why not look into using motes? search for tinyos. have a number of the receivers sprinkled about. the "mobile item" would broadcast and the sensors would receive and report. you could then do a "centroid" analysis on which motes report receiving the mobile signal and determine a likely location. Maybe even vary the mobile's broadcast strength to better isolate the closest mote. Won't give you exact location.

seems like a lot of work to find lost keys. we still don't know what problem you are trying to solve.


New Member
I am doing a project for RFID and i am just trying to put it in to a cuircuit. I know how when a tag goes through its ranges the curcuit activates. Are there any cheap applications out that i could just buy?

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