HID Hi-O iCLASS Installation Guide - Manual (Page 7)

iCLASS OEM75 Integration Guide, 3141-907, Rev. B.0
January 2014 Page 7 of 49
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2.2 Peripheral Circuits
The following section details recommended peripheral circuitry.
2.2.1 External Noise Filter
If false card detections occur in Ultra Low Power Mode, or the host has spectral noise, a line filter
designed to block frequencies in the 10 KHz to 50 KHz range is beneficial when inlined with the
power line.
2.2.2 Adding External LEDs or Beeper
Connect external LEDs to the OEM75 by connecting wires to the P2 connector The LEDs are
connected to an external +3.3VDC supply with an external series current limit resistor.
See Table 5-5: P2 I/O Electrical Specifications.
The Cathodes are connected through an external resistor to the RED or GREEN LED connector
port signals. The OEM supplies current limiting resistors for modules.
The value of these resistors will depend on how much current is provided for the LEDs. The
combined voltage drop of the resistor and output low voltage of the OEM75 on these signal lines
should be factored in when selecting the LED brightness.
2.2.3 Adding External Resistors
For I2C Mode operation, external 10k pull-up resistors are required on the SCLK signals.
Note: There is already an internal pull-up resistor on the I2C SDA signal.
2.3 Transitioning from HID’s OEM50 or eProx Lock modules
Provided are suggestions for transitioning from the HID OEM50 and HID eProx Lock modules to the
OEM75.