Low Voltage Protection On HID Smart Card Readers


HID released a bulletin PLT-02604, Rev. A.0 in May of 2016 which states Unintentional voltage drop in an electrical power supply system (commonly called “brownout”) can occur during extended main power outages and deep battery discharge. HID Global readers may become damaged when exposed to input voltages below the specified range.

The following is directly from the bulletin.


Unintentional voltage drop in an electrical power supply system (commonly called “brownout”) can occur during extended main power outages and deep battery discharge. HID Global readers may become damaged when exposed to input voltages below the specified range. This technical note outlines recommendations on how to prevent and/or address the potential adverse effects of low input voltage on iCLASS SE®, multiCLASS SE® and pivCLASS® contactless smart card readers.

To mitigate any possibility of reader damage or loss of functionality after brownout conditions, HID Global recommends that organizations take proactive steps, if not done already, to implement low voltage protection at their physical access control system power source. This best practice will protect customers against the potential adverse effects of a brownout event.

If a reader is damaged due to brownout conditions prior to implementing the electrical protection outlined in this technical note, HID Global will repair or replace the device under the terms of our industry-leading lifetime warranty policy. HID Global stands behind our stated reader performance and is committed to customer satisfaction.

Brownout Condition Overview
A brownout failure may occur when readers are powered by a physical access control panel power supply and low voltage cut-off protection is absent from the power source circuit. If back-up batteries are deeply discharged during extended main power outages, readers may be subject to input voltages below the stated specification, 5 - 16 VDC. Reader input voltage conditions ranging from 3.8 – 4.1 VDC with a 1 Vpp ripple at 10-100Hz could permanently corrupt flash memory during critical read/write operations. Based on customer reports and empirical testing, this condition is extremely rare. Readers that are affected by such abnormal power conditions will no longer read credentials, and typically exhibit one or more of the following behaviors when normal power is restored:

  • A dim white to light pink LED
  • A continuous audible buzzer
  • No LED or buzzer activity

Per device installation guidelines, the specified input voltage range for iCLASS SE, multiCLASS SE, and pivCLASS readers is between 5-16 VDC. Regional regulatory agencies, including UL and CE, have tested and approved reader performance at the extremes of this voltage range and during normal power-up and power-down conditions. HID Global recommends power supply performance be designed to provide the reader with a steady input voltage within the specified range during extended power outages.

Best Practice for Reader Installation
Customers who wish to eliminate the possibility of adverse effects during a brownout should make a simple technical adjustment to the power supply source to prevent the reader input voltage from dropping below the specified minimum value of 5VDC. HID Global recommends installation of common off-the-shelf low-voltage cutout equipment to protect devices, including readers, on the power source circuit.

This practice typically requires only one cutout device be installed at the primary power supply source of the physical access control system or control panel. In addition to protecting HID readers, these cutout devices also protect downstream devices and/or batteries from becoming damaged during extended power outage conditions.

More Information

The following is a commercially available low-voltage cutout device commonly used for this purpose:

For other makes and models, GOOGLE low voltage cut-off devices.

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  • 26-Sep-2018