RFID logger come from the assignment of one of the users of the site. He wants from me to construct, if possible, litlest data logger of RFID cards for some of his goals. After ten day I was ready with the prototype and using materials found on our markets. Today I decided to share with you how it was created. Because I will not put up for sale, I'll explain in detail what is required if you want to produce your such same device. (More information about RFID technology you can read at article for RFID emulator).
The device has the ability to read the unique code of the RFID card or key ring, and write it on micro SD card. Powered by a small 12 volt battery inside the box, can record virtually infinite cards depending on the memory card you are using. A client want's from me that the logger must be separated via cable from RFID chip, but there is the possibility of combining them in a single box.
- IC ID12LA - which is a card reader with integrated antenna. It comunicate and send Card ID information via the serial protocol. For more information, please read the technical specifications of the chip manufacturer's site.
The chip ID12LA (PDF) has verry interesting optional pins, for external antenna or for status of the presented card that can be used for your purposes. Tse size of the chip are also described in the specification. It really is a little bigger than standard chips and raster pins it is not completely standard, but the manufacturer sold boards for the purpose. I must say that there are older versions of the chip without (LA) last letters, but not recommend it because the older modification has higher power consumption.
- Serial logger OpenLog from the same manufacturer SparkFun.
He has some modes of recording the serial data, which are set by the information recorded on a text file in the SD card. The first time, it bootloader search for it and create it if it does not exist on the card. Later you can change it to your preferences. The device is quite functional for its size and I am sure that you will like to experimenting with it.
The default configuration of OpenLog file config.txt is 9600,26,3,0,1,1,0 but i use 9600,26,3,1,0,1,0 to be able to write new code to the new line of same file. More about the options of logeer you can see HERE.
Pictures can help you for connections between the logger and antenna. The only peculiarities are that:
RX and TX are exchanged between the two devices connection. i.е. RX<->TX и TX<->RX.
Another peculiarity is that I use the 12 V battery, but ID12LA operate at lower voltage. To supply it without damage take +5 V output of the linear regulator 7805 on the board. The GND is common for both devices.