Cheap small standalone 1m range RFID...is it possible?

Hi,
is it possible to develop a RFID reader that has a reading range of about 1m? Is it energy demanding?
I am just thinking about the feasibility of this.

Thanks :slight_smile:

is it possible to develop a RFID reader that has a reading range of about 1m?

Yes but they are not going to be small, the coil needs to ba large to get this sort of range.

Is it energy demanding?

No more so than a traditional RFID reader.

Thanks for the answer Grumpy_Mike.
Is there any other way to basically tell if a tagged device is within a certain (short) range?
Could nRF24L01 help me with that?
I'd like to have an active transmitter and passive labels like the ones in RFID.

Could nRF24L01 help me with that?

No.

I'd like to have an active transmitter and passive labels like the ones in RFID.

You can with UHF RFID but then it is no longer cheap.

Thanks again, so there is no technology to to this that is cheap and "small"?

Hi,
The only RFID that I have seen that has that sort of range is the Anti Shoplifting gates you walk through at shops.

About 12years ago I got to look at one from a supermarket, it had a pulse power of 500W to get the needed energy to the RFID chip to power it up, to allow it to wakeup, process and transmit its infomation.

Tom.... :slight_smile:

not to resurrect an old thread... but I am interested in a similar application and liked the feedback I read here.

The desired outcome is a system which can read 2-4 passive tags at a range of 50cm (or better).

UHF is not feasible due to cost, the experimental budget is <$100.

Reader antenna size is practically unlimited, desired tag size is key-fob size (or smaller).

looking forward to some knowledge drops!

The desired outcome is a system which can read 2-4 passive tags at a range of 50cm (or better).

As far as I know that is only available on a UHF system.

The magic words to google are:-
anti collision rfid reader

The problem is that the normal 13MHz systems while you can get some anti collision ones, will not read all the tags in a field.

Built-in anti-collision feature (at least 1 card is detected when multiple cards are presented).

from here:- RFID reader

Thank you for the quick feedback!

I might be able to concede the 2-4 and opt for 1 tag for the time being..
Does the remainder of the plan outline seem feasible?

I've seen some of your other posts and you don't seem grumpy! :stuck_out_tongue:

Well 1m range is also a challenge. You would need a bigger coil but tuned to the same frequency. It will also help if you put a bit of distance between the coil and the reader electronics.

I do believe one of my engineers did a reader with a 3ft range and an 2ft diameter coil for a passive tag for a demonstration at a show, some time before I joined them. But that was a 125KHz tag and at the show, the sales people ( muppets ) mounted the coil on a metal pillar in the hall so it didn't work and was never shown.

I read that nearby metal inhibits RFID significantly... one would think they might know that being salespeople... guess not!

Here's a question: if I needed two tags, could I have one reader with a large, tuned coil at 125kHz and another at 13.56MHz with 2 corresponding passive tags? Digikey has tags broken into those same frequencies, so I assume they are also finely tuned and would not respond to other frequencies...

Using e-m radiation ( ie a normal radio signal) rather than a magnetic field such as RFID uses could give you an enormous (>>1m) range with very little power...

Use coded active transponders and eg pager/mobile phone-type protocols to initiate a response. Look at eg pager specs. Binary subdivision of the code space is the key. Slow identification is the cost.
How many tags are there? How many in range at any one time? the ident tine is proportional to log(2) that number..

Could be done with <1mW at eg 433MHz. But the large range could be a pest! A very deaf receiver could help....

nRF2401''s could be configured to do this.

It's lots more expensive and bulky ( unless mass produced) per tag than normal RFID systems.

I'd fit the device with an activation button - like a car remote - which would synchronise the response with the base staion interrogations. Only press when you want entry.

regards

Allan

Here's a question: if I needed two tags, could I have one reader with a large, tuned coil at 125kHz and another at 13.56MHz with 2 corresponding passive tags?

I don't know but I suspect it would not. The amplifiers used in the 125KHz system are quite wide band and tends to be susceptible to to interference from all sorts of things but a near by transmitter would be one of them.

I suspect you problem, what ever it is, might be better served by an other approach.

allanhurst:
Use coded active transponders and eg pager/mobile phone-type protocols to initiate a response.

Active tag or a powered transponder are last options, passive tags are a requirement for the time being.

I understand this would be a very simple solution but the application does not permit power supplies outside of the reader module/main circuits.

Grumpy_Mike:
I don't know but I suspect it would not. The amplifiers used in the 125KHz system are quite wide band and tends to be susceptible to to interference from all sorts of things but a near by transmitter would be one of them.

I suspect you problem, what ever it is, might be better served by an other approach.

Does the interference you mention inhibit the functionality entirely? Even 1 out of 10 or 100 read attempts may still be acceptable for my application...

Just get a 500w amplifier, build a big a*s coil and start collecting your credit cards and tags info :smiley:

D.60

Does the interference you mention inhibit the functionality entirely?

It can do or it can just reduce the range.

Even 1 out of 10 or 100 read attempts may still be acceptable for my application...

It doesn't work like that. You either get a read or no read no matter how many times you try.

Does only firing one reader at a time solve the interference issue you mentioned?

Nope.

But.

a further thought.

You have an effectively infinite magnetic field power at the base station, but if you don't have a powered tag, it has only what it intercepts from the interrogating field. That small amount may be enough to activate a very small RF transmitter to respond....

experimentation required.

Allan.

There is only one reader in this setup. The interference comes from having more than one tag in the reader's field.

That small amount may be enough to activate a very small RF transmitter to respond.

That is exactly how 13.5MHz RFID cards work.