This block enables you to read RF transponder data and to write commands to the RFID sensor (via the I2C bus at hardwired address 4) connected to a selectable port.
The transponder must be of type EM4102. The ID number of a transponders has 40 bits, which are transferred as 5 bytes and provided as text string at the wire hub with a prefixed 0x. The block also converts the 5 bytes into decimal values at the outputs Raw Value 0 to 4.
The typical read distance is between 5 and 30 mm depending on the size and the orientation of the transponder.
You must drag at least one output data wire from this block’s data hub to another block for any information to be sent.
RFID Sensor and keyfob transponder
RFID stands for Radio Frequency IDentification. The RFID Sensor is transmitting a low frequency radio signal (125 kHz) via its integrated ferrite antenna. This electromagentic wave is activating the transponders by inducing energy into the transponder's coil. The transponder then starts modulating this signal according to its number which is stored in a non volatile memory. This modulated signal can be detected (demodulated and decoded) by the RFID sensor.
There are some advantages and restrictions of the RFID technology. A major advantage is that the transponders are passive, meaning that they do not need any internal battery, giving them an almost unlimited lifetime. Another advantage is the identification without line of sight, even with material (non metallic) in between the RFID Sensor and the transponder.
One restriction is the limited reading distance, due to the fact that the energy for activating the transponder has to be transmitted from the RFID Sensor. Also the orientation of the transponder versus the ferrite antenna is a limiting factor for the achievable reading distance. Look at the picture below to see optimal transponder orientation:
The circles represent the transponder's coil. If the coil is oriented like the blue circles show, reading distance is optimized. The read circles orientation result in low or no even no reading distance.
In your application you have also to keep in mind, that the modulated transponder signal can be disturbed by any electrical noise (coming from motors, fluorescent lights, electrical switches, a.o.). In this case the RFID Sensor may not decode the signal properly resulting in bad or no reading. The bigger the distance of the transponder from the sensor is, the more critical is the noise influence.
You can minimize this effect with repeated reading and reducing the distance between RFID Sensor and transponder.
Following commands are available:
- 0 Reader Stop: The RFID sensor
stops any reading and goes into power saving Sleep Mode!
- 1 Single read: With this command
you can force the RF sensor to do a single read. If a transponder is close
enough to the antenna, the transponder data will be read and information
provided to the corresponding wires! The maximum read rate is app. 3 reads per second!
After execution of a single read command the RFID sensor will enter the Sleep
Mode!
- 2 Continuous read: This command
forces the RF sensor to continuously reading available transponders. In this
mode you achieve the highest read rate. You can read up to app. 10 reads per
second by repetitive use of the block
in a loop! If there is no read or any other command on the I2C bus for app. 2
seconds, the RFID sensor will automatically enter the power saving Sleep Mode!