28140 Parallax Inc, 28140 Datasheet - Page 5

• Manufacturer Part Number: 28140
• Description: READER MODULE RFID
• Manufacturer: Parallax Inc

Specifications of 28140

• Rf Type: Read Only
• Frequency: 125kHz
• Features: Single 5V Power Supply
• Package / Case: Module
• Product: Microcontroller Accessories
• Data Bus Width: 8 bit
• Clock Speed: 125 KHz
• Interface Type: USB
• Operating Supply Voltage: 5.5 V
• Board Size: 46.99 mm x 69.22 mm x 21.84 mm
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

Optional Tag Information
Even though Parallax only carries a Round Tag and a Rectangle Tag the following values were obtained
from different tags available in the market.
ISO Card:
World Tag 50mm:
World Tag 30mm:
Bobsleigh Keyfob:
Tear shape:
Wristband:
RFID Technology Overview
Material in this section is based on information provided by the RFID Journal (www.rfidjournal.com).
Radio Frequency Identification (RFID) is a generic term for non-contacting technologies that use radio
waves to automatically identify people or objects. There are several methods of identification, but the
most common is to store a unique serial number that identifies a person or object on a microchip that is
attached to an antenna. The combined antenna and microchip are called an "RFID transponder" or "RFID
tag" and work in combination with an "RFID reader" (sometimes called an "RFID interrogator").
An RFID system consists of a reader and one or more tags. The reader's antenna is used to transmit
radio frequency (RF) energy. Depending on the tag type, the energy is "harvested" by the tag's antenna
and used to power up the internal circuitry of the tag. The tag will then modulate the electromagnetic
waves generated by the reader in order to transmit its data back to the reader. The reader receives the
modulated waves and converts them into digital data. In the case of the Parallax RFID Reader Module,
correctly received digital data is sent serially through the SOUT pin.
There are two major types of tag technologies. "Passive tags" are tags that do not contain their own
power source or transmitter. When radio waves from the reader reach the chip’s antenna, the energy is
converted by the antenna into electricity that can power up the microchip in the tag (known as "parasitic
power"). The tag is then able to send back any information stored on the tag by reflecting the
electromagnetic waves as described above. "Active tags" have their own power source and transmitter.
The power source, usually a battery, is used to run the microchip's circuitry and to broadcast a signal to a
reader. Due to the fact that passive tags do not have their own transmitter and must reflect their signal
to the reader, the reading distance is much shorter than with active tags. However, active tags are
typically larger, more expensive, and require occasional service. The RFID Reader Module is designed
specifically for low-frequency (125 kHz) passive tags.
Frequency refers to the size of the radio waves used to communicate between the RFID system
components. Just as you tune your radio to different frequencies in order to hear different radio stations,
RFID tags and readers have to be tuned to the same frequency in order to communicate effectively. RFID
systems typically use one of the following frequency ranges: low frequency (or LF, around 125 kHz), high
frequency (or HF, around 13.56 MHz), ultra-high frequency (or UHF, around 868 and 928 MHz), or
microwave (around 2.45 and 5.8 GHz). It is generally safe to assume that a higher frequency equates to
a faster data transfer rate and longer read ranges, but also more sensitivity to environmental factors such
as liquid and metal that can interfere with radio waves.
There really is no such thing as a "typical" RFID tag. The read range of a tag ultimately depends on many
factors: the frequency of RFID system operation, the power of the reader, and interference from other RF
devices. Balancing a number of engineering trade-offs (antenna size v. reading distance v. power v.
Parallax, Inc. • RFID Reader Module (#28140) •Updated 02/2006 v1.1
6.3cm (2.5") +/- 10%
6.8cm (2.7") +/- 10%
5.3cm (2.1") +/- 10%
5.3cm (2.1") +/- 10%
4.0cm (1.6") +/- 10%
4.0cm (1.6") +/- 10%
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