I am working on a prototype, one function of which is to detect whether an object is "in range" by a few cm. Right now I'm just using an Arduino and a cheap Mifare RC-522 kit that operates at 13.56 MHz:
I've successfully gotten it to detect the tag, but only at a distance of about 3-4 cm when the tag is oriented parallel to the antenna.
I realize this inexpensive reader is not up to task as-is, but I'm interested in building something that achieves read ranges of 15-20 cm.
- No need to read multiple tags; only whether one tag is in range or not.
- No need to write to the tag.
- Cannot use an active tag.
I'm not experienced with RFID reader construction (yet) but am interested in knowing what I should pursue.
Here are some things I've considered:
- Ditch the embedded antenna on the cheap RFID reader and construct my own, larger antenna. I'd need to see if the onboard MFRC522 is up to the task of providing additional power.
- Look for a different IC around which to build a reader from scratch.
- Find a ready-made solution instead of trying to build one (more cost-effective?).
- Use something other than RFID for simple proximity detection.
I am experienced with microcontrollers and basic electronics, and have made audio and lighting projects, but this is a first with RFID. Since I don't need to read multiple tags, which RFID is suitable for, I've considered maybe some sort of magnet and hall-effect sensor, but the range does not seem adequate. I considered using an ultrasonic proximity detector, but the application calls for detecting the tagged object while ignoring untagged ones (ultrasonic would produce false positives on untagged objects). I've considered some sort of reflective surface placed on the object, and detecting reflected light, but the object orientation is not reliable enough to maintain alignment.
So, in a nutshell, What modifications can I make to my existing reader, or what alternate technology should I pursue to achieve 15-20 cm detection of a passively tagged object?
I plan on connecting whatever proximity detector is used to a microcontroller using SPI.