EM18 RFID Reader is a module which reads the ID information stored in RFID TAGS. This ID information is unique for every TAG which cannot be copied. Working frequency is 125KHz for EM18 TAGS and these tags are READ only , you cannot write on these tags.
EM-18 Features and Specifications
Operating  voltage of EM-18: +4.5V to +5.5V
Current consumption:50mA
Can operate on LOW power
Operating temperature: 0ºC to +80ºC
Operating frequency:125KHz
Communication parameter:9600bps
Reading distance: 10cm, depending on TAG
Integrated Antenna
 
 
Pin Number
Description
VCC
Should be connected to positive of power source.
GND
Should be connected to ground.
BUZZ
Should be connected to BUZZER
NC
No Connection
NC
No Connection
SEL
SEL=1 then o/p =RS232
SEL=0then o/p=WEIGAND
TX
DATA is given out through TX of RS232
DATA1
WEIGAND interface DATA HIGH pin
DATA0
WEIGAND interface DATA  LOW pin
 
EM-18 can provide ouput through two communication interface. One is RS232 and another is WEIGAND. The form of communication is selected by SEL pin.
If SEL pin is selected HIGH then form of communication is RS232 and if SEL pin is pulled LOW then form of communication is WEIGAND. Usually the RS232 is selected because it’s popular so SEL pin is pulled HIGH.
         The output of MODULE bit rate is 9600bps (bit per second). The controller should be programmed to receive information from MODULE at this rate. If bit rate of controller mismatches then the system will not work correctly.
When a TAG is brought near the MODULE it reads the ID and sends the information to controller in 12 ASCII CHARACTERS. In them, 10CHARACTERS represent the TAG ID and 2 CHARACTERS are XOR of previous 10 CHARACTERS.
So DATA sent = 10ASCII DATA (tag no.) + 2ASCII DATA (XOR result)
Once the Information is sent, the MODULES stop sending DATA. This serial DATA received by the controller though RX pin contains TAG information which is ready for processing. We can program the controller to save the DATA or process it to provide response immediately.