1.0 Introduction

The following information explains how to install the NXT-2D or NXT-4D controllers and peripherals that connect to those controllers. Other wiring diagrams and additional NXT installation information can be found in the NXT-4x4, NXT Reader and NXT-RM3/WI+ installation guides.

2.0 Important Note:

Keri Public Statement on the Amazon Key

3.0 Wiring and Layout Diagrams

3.1 NXT-4D Installation Drawing

Notes:

• This equipment has been tested and found to comply with the limits for a Class A digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference when the equipment is operated in a commercial environment. This equipment generates, uses, and can radiate radio frequency energy, and if not installed and used in accordance with the instruction manual, may cause harmful interference to radio communications. Operation of this equipment in a residential area may cause harmful interference in which case the owner will be required to correct the interference at the owner’s expense.
  
  
  
  • PCBs revision M and later only have 2 x Ethernet activity LEDs (A and B).
    
    

  • This controller uses a CR-2032 3 volt backup battery that retains all controller configuration and cardholder records if the controller is down-powered. The voltage level of the battery should be checked annually.

    
    

3.2 LED Definitions Table

1. PCBs at revision M or greater have only 2 Ethernet communication LEDs (D21 and D22).
   PCB revisions earlier than M also have the D33 (Activity) LED.
   
   
2. If LED s is green, the power wires are reversed; if LED s is red, the unit is drawing too
   much current.
   
   
3. PCBs at revision F or greater have the RS-485 Bus Over Current LEDs t, u, v, and w.
   PCB revisions earlier than revision F do NOT have these LEDs.
   
   
4. If LED t, u, v, or w is red, that individual bus is drawing too much current and the bus
   is shut down to protect the controller. When this condition is corrected, the LED will
   turn off and the bus will be activated.

3.3 Wiring a Fail-Safe Lock

3.4 Wiring a Fail-Secure Lock

3.5 Lock Port Protection

Transorbs are provided with the controller ship kit. They are used to protect the controller from
voltage spikes induced on the port wiring by absorbing the excess voltage and slowly releasing it
back into the circuit. Keri strongly recommends wiring in the transorbs provided with the controller
ship kit. Refer to the Transorb Wiring Diagram below.

Note: The transorbs that Keri provides are non-polar; they can be installed in either
orientation.

3.6 Using Isolation Relays

For locking devices that may induce heavy voltage spikes – Mag Locks and devices with heavy-duty solenoids such as turnstiles, vehicle gates, and overhead doors – Keri recommends using isolation relays.

​

Please refer to the IRP-1 Isolation Relay Installation Guide (p/n 01833-001) for further detailed information.

4.0 Wiring Instructions

4.1 Terminal Blocks

Note: Screws on terminal blocks must be tightened securely.

4.2 Connecting the Earth-Ground and the 12VDC Power

5.0 NXT Controller Earth-Grounding

5.1 At the Controller's Metal Enclosure

To ensure optimum earth-grounding of the controller and its connected peripherals, you should make a quality earth-ground connection to the metal enclosure lug (which displays an adjacent earth-ground symbol).

This good-quality earth-ground at the enclosure lug will provide an earth-ground for the entire enclosure - and will therefore ground anything that is connected to the metal enclosure - (the four metal screws at each corner of the PCB) - plus, through circuitry on the PCB, this includes anything connected to the lug marked J6 or pin 3 of the TB10 power connector.

In addition, the enclosure itself must be earth grounded to a good quality ground point external to the enclosure for a complete path to ground.

5.2 At the Controller's Earth-Ground Lug

NXT controllers have Ground Lug J6 at the top of the PCB near the TB10 power connector. Make your NXT earth ground connection directly to this lug.

6.0 Grounding RS-485 Devices and Readers

The shield/drain wire of any reader/peripheral cables MUST be terminated to one of the following points: any corner screw attaching the controller to the enclosure, Pin 3 of TB10, the green ground lug (J6) on the controller, or the ground lug of the enclosure. Failure to properly earth ground the reader drain wire may result in unreliable communication or operation of the attached peripheral.

The following diagram illustrates correctly grounding an NXT reader at the controller.

7.0 Controller Maintenance

7.1 The 3-volt Lithium Backup Battery

The controller's backup battery retains all controller configuration, including cardholders and this information is completely cleared if the controller loses power - (when the battery is flat or low voltage).

Once the controller is powered back up, an update must then be performed on the controller - to re-send the controller configuration and cardholders.

Notes:

When changing the controller's backup battery you should do the following:

1. Check that the controller is online - so you will be able to update it.
2. Ensure that the controller is down-powered when you remove the 3 volt lithium battery.
   - failure to do so may permanently damage the controller.
3. Perform an update on the controller after changing the controllers backup battery.
   - the controller will need to be configured again when the battery has been replaced.

7.2 The Power-Supply Backup Battery

Many installations also use backup batteries connected to the power supplies - this will keep the
controller powered-up for a certain amount of hours if there is a power-outage at the site. Again,
these backup batteries should be checked every 18 months-2 years.

After a while, battery backups on the power-supply may develop a fault - often causing them to
draw more current from the power-supply. With certain power-supplies this may result in less power
being available for the controller and its connected peripherals - If you disconnect the PSU backup
battery, and the voltage is low, then it is likely that the battery needs replacing.