RFID Questions??

[Jeff_5_7]

ok so im new to RFID and looking for some help here are some questions i have..

1 With a passive tag can you turn it on and off or is it just on all the time?

2 What is the role of the microprocessor in the reader and Do you have to have a microprocessor to control the reader chip?

3 Where can i get some schematics for a reader circuit? (ex. The Texas instruments reader and the like)

4 Does a pasive tag work well in an electrically nosiey environment. (ex under a car hood with all the spark plugs and wires.)

5 Are there any FCC rules and regulations with RFID?

6 Do passive tags work good in a 3 to 5 foot range?

thanks guys i appreciate the help and will probably have more questions soon.

 

[Jeff_5_7]

Anybody?????

 

[DSGarcia]

ok so im new to RFID and looking for some help here are some questions i have..

1 With a passive tag can you turn it on and off or is it just on all the time?

2 What is the role of the microprocessor in the reader and Do you have to have a microprocessor to control the reader chip?

3 Where can i get some schematics for a reader circuit? (ex. The Texas instruments reader and the like)

4 Does a pasive tag work well in an electrically nosiey environment. (ex under a car hood with all the spark plugs and wires.)

5 Are there any FCC rules and regulations with RFID?

6 Do passive tags work good in a 3 to 5 foot range?

thanks guys i appreciate the help and will probably have more questions soon.

1) Actually the tag is off all the time. The field created by the reader allows the tag to charge with enough energy to transmit its information.

2) It depends on the reader. Of course, there will be an imbedded microprocessor of some sort in the reader, but I assume you are speaking of your own processor. Some readers have a serial interface where you can use a PC or any processor with a serial interface. It depends on the interface of your reader and what you want to do with the information read from the tag.

3) Check the manufacturer's web site. You may first wish to search for reader manufacturers or perhaps search electronic distributors such as Mouser, Newark, Allied, Digikey, etc. for RFID readers then click on the link to display the datasheet.

4) Depending on the noise, you should probably be ok. There is a problem however when there is lots of metal around the antenna or particularly between the reader antenna and the tag. The tag cannot be mounted on metal, but you can punch a hole in the metal or add a plastic spacer to keep the tag away from direct contact with the metal.

5) There are FCC rules for just about anything that transmits an RF signal. If you get a licensed reader you should be ok. If you build one from scratch, then you will have to check the FCC rules. I don't know specifically what they require, I always bought certified RFID readers. The manufacturer of your reader should be able to provide some help.

6) It depends on the antenna design and the surrounding environment (i.e., metal). You can purchase a gate antenna which will read tags that pass through if that would work for your application.

By the way, what is your application and what are you trying to accomplish?
Thanks,
Dale

 

[Jeff_5_7]

thanks but i still have some questisons

with a passive tag can you control the output of the tag with a sensor (ex if i want to hook the tag to a temperature sensor so that if the temp sensor senses a temp within a certain range the tag will transmit the signal to the reader but if the sensor reads a temp out of the range the tag wont transmit to the reader can this be done?? i hope you guys understand me here.)

Can i get tags that have the same code?? Say i have 100 tags with the same code i want one reader to be able to read them almost like universal.

How do i get around the reader trying to read more than one tag at once if they all have the same code though i have heard something about a delay in the tag??


As far as my application it is pretty much vehicle immobilization
thanks guys

 

[DSGarcia]

thanks but i still have some questisons

with a passive tag can you control the output of the tag with a sensor (ex if i want to hook the tag to a temperature sensor so that if the temp sensor senses a temp within a certain range the tag will transmit the signal to the reader but if the sensor reads a temp out of the range the tag wont transmit to the reader can this be done?? i hope you guys understand me here.)

Can i get tags that have the same code?? Say i have 100 tags with the same code i want one reader to be able to read them almost like universal.

How do i get around the reader trying to read more than one tag at once if they all have the same code though i have heard something about a delay in the tag??


As far as my application it is pretty much vehicle immobilization
thanks guys

They make temperature sensing RFIDs for cattle. Perhaps a search will turn up something. However, I don't know much about the temperature range they measure. The tag will always transmit the temperature and will not "be quiet" outside a certain range. You can do that part with your processor hooked up to the reader.

All tags I know about have unique codes. Talk to a manufacturer about duplicate codes, but I expect it would be expensive and they would require a very large order. It is better for you to have a list of "approved" tags. That would also be better in case one of your desired duplicate tags fell into the hands of an unauthorized user; you could unlist the missing tag number.

The tag will transmit when the reader scans the tag. The reader will read the ID of whatever transmits. The tags have no delayed transmit.

 

[Jeff_5_7]

how can i get a tag to work with sensors like pressure temp and motion im pretty sure u can do it but i think it has to be an active tag i would like to do it with a passive tag do you know anything about this.

 

[kchriste]

The passive tag gets its energy from the reader via RF so the power available is tiny. So unless the sensor uses microwatts of power, you'll have to use an active, or powered, tag.

 

[DSGarcia]

Jeff,
In addition to adding a temperature requirement, you are now adding pressure and motion requirements. At this point, you are getting beyond the capabilities of an RFID tag; you need a small data acquisition system. You can make your own system with a microprocessor with the sensors and inputs you need.

Your microprocessor can provide the "ID". To prevent unauthorized access, I would recommend you implement a challenge/response protocol so someone doesn't just duplicate your transmissions to fool your system.

There are a number of wireless communications methods you can use. You will need a power source for this but there are techniques to minimize the power requirements.
Dale

 

[Jeff_5_7]

i understand how a passive tag works what i want to know is can i get a tag that is hooked up to a temp and pressure sensor? Meaning MY temp sensor with read a temp in a range and if the pressure sensor has pressure applied then the tag will transmit to the reader. But if my pressure sensor dosnt have pressure applied and my temp sensor dosnt read in my temp range then the passive tag wont transmit to the reader even if its in range of the reader can this be done?? Im almost sure you can do it with a semi passive or active tag but im trying to stay away from a battery. I just want the 2 sensors to control the output of the tag.

 

[DSGarcia]

Without a source of power you cannot drive and sense the output from a pressure transducer or power its supporting circuitry. I do not know of any RFID tags that can be hooked up as a data acquisition system, especially passive tags. Sorry, I am unable to help you with your application as you have defined it. I have only used RFID tags for identification, the part "ID" part of RFID.
Dale

 

[Jeff_5_7]

well im almost sure it can be done just nobody here knows how i do know it is complicated there is company called gentag that makes a passive tag that measures body temp and sends it to a reader so i think i can do it

 

[DSGarcia]

Jeff,
If you go to the Gentag web site, you will notice they have a few specialty patented sensors (such as temperature) integrated with the tag electronics. [I mentioned a cattle tag earlier that also read temperature.] The Gentag tags have no external interfaces that I have found. Perhaps if you call them they can make a few million of them to your specifications.

If you want to make your own tag, I can tell you that there are a lot of really smart and experienced people on this forum and perhaps there is a reason more don't respond. When you come up with a passive RFID tag that does data acquisition and control, there are probably a lot of people that would be interested. Good luck and let us know when you have it ready.

Just exactly what are you trying to do anyway?

Dale