Hello everyone! I've had some great help here before, so i was wondering If I could get some opinions? I'm thinking of putting together an RFID system that has the following functionality:
At a set time every day, the reader "scans" a 1 meter square area (approx) for 10 separate RFID tags. If one of these tags is not present, it sounds an alarm. Ideally the tags should be cheap, stick-on things like a shop security system and probably "passive"?
If I buy a Parallax RFID reader, do you think I can get this functionality? I think, form reading other posts, that I need collision control and a range of about one meter. Do I need HF RFID - and has anyone had any success with that?
125Khz RFID would definitely not work as it has a very short range. You may get away with 13.56Mhz which has a longer range, but I would recommend going with UHF at 860Mhz which works up to about 6m or more and has anti collision for up to 50 tags on most systems. It is the most expensive though, but if you shop around you can get some decent prices. I would have thought the extra range of UHF would be worth it so you can expand the system easily in future to include a wider area.
Thanks for your answer! I've been looking for a 13.56 system or a UHF system, but i'm keen to be able to easily interface with an arduino (or similar) , and all the things i've found seem to be at industry volumes and prices. Does anyone know where I might be able to get system at a hobbyist level? maybe i'm searching for the wrong things...
That system may not be RFID in the standard sense, ie it may not use the normal frequencies, and is just a cheap transmitter and receiver at 433Mhz (which are available very cheaply compared to RFID readers).
They would have to be active tags for a true RFID system to get that sort of range, and these are more expensive than the passive tags.
They would have to be active tags for a true RFID system to get that sort of range
No. From this and a previous post I see you knowledge of RFID is not the most comprehensive.
You can get this sort of range from passive tags especially the higher frequency ones. Even with the lower frequency ones and the right sort of antenna design you can get this sort of range. It is the anti collision requirement, that is reading more than one RFID in the same field that makes this request more complex.
Even with the lower frequency ones and the right sort of antenna design you can get this sort of range
Reading the review of the product from the link it says that it can go to 30 feet (9 metres). How can a lower frequency tag achieve this sort of range without being powered?
Thats why I imagined it would have to be UHF to get this sort of range, and you wouldn't find a UHF reader at the price range of the product.
1.5 meter range using a 60cm diameter coil operating on a passive tag
Thats a big difference to a 9 metre range though (as the product has)...
Is it possible to create diy reader solutions?
Yes definately, have a look at the EM4095 chip which is pretty easy to use, I created my own system with this chip and an Arduino. Also there is the U2270B from Atmel. Both are low cost, and work with 125Khz tags
True but the original poster was only asking for a 1M square. If you go to an active tag you can get a much bigger range. The problem with a big range on RFID is that people walking past can set it off not those just wanting to get through the door. Imagine walking down a corridor and opening every door you walk past.
have a look at the EM4095 chip which is pretty easy to use
But it is expensive, you can do it for a lot less from a hand full of parts.
But it is expensive, you can do it for a lot less from a hand full of parts.
They're only £3.50 for single quantities, and they make life a lot easier, especially when handling the manchester decoding. They need very few external parts as well, so you can make a complete reader for very little.
They are £3.85 there at the moment (I haven't bought any for a while). You can also get them from China at around £3 each (still in single quantities).
The U2270's are only £1.49, but need more external components.