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Low-frequency RFID transponders communicate with low-frequency RFID readers by something called inductive coupling. The coiled antenna in the reader antenna and the coiled antenna in the tag form an electromagnetic field. Changes in this field allow readers to send commands to tags, and tags to send data to readers. Think of it this way: You and I each have a hand on a balloon. I squeeze the balloon with short and long squeezes to communicate in Morse code. You then respond to my questions by doing the same.
The read range between the tag and the reader depends on the size of this electromagnetic field. The size of the field is determined by the size of the loop in the reader antenna, and by the power output of the reader antenna. It is possible to create an electromagnetic field that is roughly 3 feet (1 meter) in diameter. You could reach out to the reader maker to see if there is a way to use a different antenna or increase the power output.
If there are any experts in LF RFID technology with more insights, they are invited to post comments below.
Founder and Editor
The RFID realm of LF is not ISO standard and there are many different eeprom chips. Chips like EM4200, T5577, Q5, Hitag, etc. all have different memory mappings, often times different modulation techniques, ASK versus Manchester versus FSK, etc. Readers have firmware expecting to see a particular eeprom. If a Reader is made to operate with a read only EM4200 (aka 4100, 4102 and other previous generations) chip, any read only Tag from another source will work. If you use a Q5 Tag, it will not work. My first guess is you’ve got mismatched Tags and Reader, but there could be more troubleshooting to be done. Have you established communications with the Reader? Maybe the Tag is being read but not shown on your PC. Does the Reader have an indicator, say an LED, that shows power is applied and blinks say when a Tag is read? This would tell you the Reader is operational and reading the Tag, but no communications established with your PC. The issue could get deeper. The chip could very well be compatible. If the Tag was programmed in Manchester and your Reader is expecting ASK, the Tag would need to be re-programmed with your Reader. The folks at Sparkfun are wonderful and they offer easy to use products for hobbyist, students, and simple applications, but you get what you pay for. Higher end LF Readers can run as much as $1100. Please reach out to email@example.com if you’d like more assistance.
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