RFID type sensor with 2 to 3 meter range?

Is there anything like RFID that can work in a 1 to 3 meter range while maintaining a small footprint on the detected object side? Like something close to the size of a quarter?

I'm wanting to detect the presence of something at a range of 2 to 3 meters, but I want it small enough to easily and comfortably go on a key ring that goes in my pocket. It seems like the small RFID tags that are the ideal size, are usually limited to about 10mm, much to short for my application. Any type of RF device that I've seen seems to big for my goal and also I was hoping there was something like passive RFID tags that didn't require any sort of power.

I know some cars have features now that detect the key inside the car and won't let you lock the doors, does anyone know what method those devices use? Those are probably battery powered I imagine since I'm sure it's something in the Key FOB transmitting a signal, but whatever it is, is low enough power usage to not need battery replacements for years. I'd prefer not to have another key FOB sized object on my key ring, one key FOB is enough lol.

You'll be needing UHF (900Mhz) tags and readers. Readers and antennas are quite bigger and more expensive than the usual 125KHz or HF tags.

Is there anything like RFID that can work in a 1 to 3 meter range while maintaining a small footprint on the detected object side? Like something close to the size of a quarter?

No.

RFID's short range is part of it's security, else anybody could scam a persons rfid enabled credit card by simply passing them in the street, unfortunately this has been proved, on the plus side the antenna used stands out like a sore thumb

For meters range i would use NRF21L01 modules

Hmm, the UHF looks interesting, but it is apparently not very popular for small projects. Can’t find anywhere selling small quantities for it. What small dimension tags I could find weren’t bad, 3 to 6 dollars each (but wanting orders of 100 or more lol), but the cheapest reader I saw was 265 which is a lot more than I’d like to spend atm.

I’ve got some nrf24L01s, but the size of them… by the time I added a MCU and battery, anything I could fabricate would be just as big or bigger than my keyless entry remote. Not to mention the only MCU I’ve been able to get to work with them is the ATMega’s which aren’t exactly small themselves (at least not the ones I’ve used). Not to mention the battery life on them would be less than ideal. How could you make them sleep when in the presence of a reading station but already read? Unless the nrf24L01s have a feature of detecting nearby nrf24L01s without actually talking to them that I’m not aware of?

Really 1 meter range would be plenty, I could even get by with a 30 to 50 cm. The longest range RFID I’ve seen is more like 10mm though, a couple that claimed 3 inches and that was with a credit card sized tag, that is to large of a tag and to short of a range.

So what part of no do you not understand?

Grumpy_Mike: So what part of no do you not understand?

Oh I understand no just fine, I simply ignore it when it's incorrect. And sometimes I'll ignore it when it looks to be correct because if you never try to find a way around a problem, you'll never get around the problem.

However, if I had the money to spend on it UHF would work, so your 'No' in this case is simply incorrect.

I spent five years designing RFID readers and even if you had the money it woul still be no. :P

Grumpy_Mike:
I spent five years designing RFID readers and even if you had the money it woul still be no.
:stuck_out_tongue:

Care to explain then? Everything I’m reading about UHF says it works at up to 30 feet generally. And there are passive tags available smaller than a quarter. Looks like both of those meet my requirements. How is it still no?

Regardless, I know what I want to achieve is possible, because it exists as features in cars made today, I’ve seen it work. It just might work a little differently than my line of thinking. I’m not using it for the same purpose as not locking keys in the car, but it’s a similar application.

Trouble with UHF tags is that they come in huge quantities. Some sellers offer a sample pack, but most of the time they charge between $50 and $100 dollars for it.

In UHF tags, you have to take into consideration the type of surface you are attaching the tag to (is it metal, paper, etc).

There are some development boards, but they are not cheap.