RFID Reader Systems

The predominate sources of RFID reading systems suitable for sediment tracking in North America are Aquartis, which is no longer active, Texas Instruments, which has done substantial work in

developing RFID equipment but provides minimal technical support, Biomark, which actively markets to fish and wildlife research community, and OregonRFID who manufactures and distributes equipment for RFID tracking and provides substantial technical support both before and after sales of their products.

One of the common reader systems mentioned in RFID tracking literature is the Texas InstrumentTM

RI-STU-251B series 2000 combined tuner-reader-control module (Morhardt, et al., 2000; Lamarre, et al.,2005). The RI-STU-251B has an auto tuner coupled with reader and control module, with the auto tuner suitable for antennas with an inductance range between 26 – 27.9 µH at 134.2 kHz (Texas Instrument, 2000). This system is demonstrated for fish tracking by Morhardt et.al (2000) as shown in Figure 41. Since they use the Texas InstrumentTM _{RI-ANT-S02 stick antenna with an inductance of}

27 µH, the antenna can be directly connected to the auto tuning reader. The reader has a serial output which can be configured to automatically send the tag ID every time a tag is detected.

More control and flexibility of the system can be accomplished by using separate reader, controller, and tuner as accomplished by Schneider et.al (2010). They used the Texas InstrumentTM _RI-RFM-

008B reader, RI-CTL-MB2B control module, and RI-ACC-008B tuning board; enabling them to use two different antenna of their own custom design. They experimented with flat bed antennas ranging in width from 3.5 m to 4 m and ranging in length from 1 to 2 m to determine the optimal geometry for maximizing read range. By using a separate tuner module, the range of inductances of the different antenna geometry could be accommodated and driven by the same reader.

To record detected RFID tag numbers, the data needs to be communicated from the reader to some other device via serial communication. There are many options for serial communication with the reader. The reader can be connected to a data logger which can periodically be downloaded to computer or stored on a removable SD card. The serial port from the reader can be directly connected to a palmtop computer (Allan, et al., 2006), connected to the serial port on a desktop computer, or connected through a serial to USB converter. Once the connection is established with a the computer, the serial data can be read on the COM port which the computer has assigned to the serial

communication device by using a terminal emulator program such as HypterTerminal which comes with window versions prior Windows 7 or PuTTy (http://www.putty.org/) which will can be configured to log data from the serial port and record it to a text file.

The serial data from a reader can also be read by an Arduino micro controller. These are dedicated control units which are becoming popular in educational environments due to their low cost, ease of programming, and direct input and output capabilities. The Adruino can be coupled with an LCD for readout, enabling a low-cost field display to be created. When connecting to an Arduino, a voltage converter chip must be used because serial port standard is for a on bit (1) represented by a -13 volts and an off bit (0) represented by +13 volts (upper chart in Figure 40), wherein the Arduino uses TTL logic in which on bit (1) is +5 volts and an off bit (0) is 0 volts (lower chart in Figure 40). A Max 232 Serial to TTL module (https://www.sparkfun.com/products/13029) can provide this require

conversion.

Figure 40 Serial and TTL levels (RS-232 vs. TTL Serial Communication, 2010)

A Bluetooth dongle can also be connected to the serial port on the reader to enable transmission to Bluetooth on a computer (Bradley & Tucker, 2012) or a smart-phone. Bluetooth is a wireless networking technology transmitting radio waves at 2.4 GHz and establishing a small network, referred as a piconet with 2 to 8 nodes. The range of communication is a function of the class of Bluetooth being used as shown in Table 4.

Device Class Transmitted Power Intended Range

Class 3 1 mW Less than 10 meters

Class 2 2.5 mW 10 meters

Class 1 1000 mW 100 meters

Table 4 Bluetooth Device Transmitter Classes (Wright, n.d.)

If a Bluetooth device does not have the class stated, it will likely be a class 2 or 3 device. Because of the higher design requirements of Class 1 devices, the documentation on Class 1 devices commonly states their class designation as seen in products such as the GridConnect Serial to Bluetooth Adapter – Firefly (http://gridconnect.com/serial-to-bluetooth.html) or IOGear Long Range Bluetooth USB Adapter (https://www.iogear.com/product/GBU321/). The Firefly and IOGear USB adapter can be used together in conjunction with a computer to provide serial communication over Bluetooth. When using this method of communication, the GridConnect Serial to Bluetooth adapter needs to be configured to receive serial communication from the RFID reader at the baud rate set by the reader, while the computer needs to establish a serial connection with the IOGear using the baud rate set on the GridConnect for serial over bluethooth transmission (GridConnect, 2007).

Bluetooth communication can also be achieved between a reader and a cellphone equipped with Bluetooth. Wherein on a Windows based PC, the control panel indicates the COM port designated to the serial port over Bluetooth and the baud rate can be controlled by the user, cell phone users are not provided this level of control. A review of literature and websites indicates that the cell phone may automatically set the appropriate baud rate through the “Remote Port Negotiation Command” (Bluetooth, 2001). This would indicate that if the FireFly’s serial over Bluetooth baud rate is set to a common value such as 9600 or 115200 bps, then the terminal emulator application on the cell phone should automatically query the FireFly and establish port settings.

Rather than using wireless communication, the serial data has also be read directly by a Hewlett Packard 48GX programmable calculator with serial communication capabilities as shown in Figure 41 (Morhardt, et al., 2000). Rather than needing to connect all 9 pins of the DIN 9 serial port, the only pins required for communication are the transmit (TXD), receive (RXD), and ground (gnd) pins. The HP 48GX has been discontinued. However, an HP 50G graphing calculator has the programmable functionality and is equipped this a USB port. By purchasing an HP 50g RS-232 Serial Cable (http://commerce.hpcalc.org/serialcable.php) for US$20, the HP 50C can be connected to read data from a serial device such as an RFID reader.

Figure 41 Schematic of connection between antenna, reader and data-logging calculator (Morhardt, Bishir, Handlin, & Mulder, 2000)