This tutorial will help you learn to use our Base Station graphical user interface to control ProXR USB Relay Controllers.  Base Station is the software we use to demonstrate the features of our devices.  Base Station works by identifying the controller.  This software will generate a list of compatible control panels and demonstrate each individual feature.  This tutorial will display the bytes of data required to control our entire line of USB Relay Controllers.  This makes integration into your own software effortless, regardless of language or platform.  NCD USB Relay Controllers will act as a virtual com port on your PC.  Simply open the port and send your data to begin controlling relays.  Download Base Station Software from // Base Station software is compatible with Windows 8 and Windows 10.  The latest Dot NET framework must be installed when working with older operating systems.

USB Relay Controllers: A Complete Tutorial

This guide covers all ProXR series controllers, we will primarily be focusing on using USB ProXR and ProXR Lite Series controllers for communications as this is the preferred technology for product discovery and initial testing.  Base Station software supports other interface technologies including Wireless, Ethernet, Wi-Fi, Bluetooth, and RS-232, the directions are largely the same for all of these technologies as all communication modules communicate to the ProXR controller using serial data.  USB Controllers mount as a Virtual COM port on your computer.  Most Windows PCs include the drivers necessary to talk to our controllers; however, a comprehensive list of supported drivers and operating systems are available at

Once the controller is plugged into the USB port of your computer, the USB LED should light on the USB interface module plugged into the controller.  If this light does not illuminate, your computer has not properly enumerated the USB driver (please see the link above install the latest drivers).

Communications to any NCD controller is as easy as sending bytes of data out the serial port or virtual COM port.  The default baud rate for all ProXR and ProXR Lite devices we manufacture is 115.2K Baud, 8 Data Bits, 1 Stop Bit, No Parity. NCD controllers expect to receive raw bytes of data for best possible speed. For this reason, common terminal programs should only be used in a way that supports raw data bytes rather than ASCII. The tables in this guide are shown in Hexadecimal values by default with an option to display commands in decimal values using a button above each table labeled “Show as Decimal”. All NCD ProXR class controllers are “Speak When Spoken To” devices.  Send a command and receive a response. The Hex values shown should be sent out the communications port (TX Portion of the table) and the controller will respond (RX Portion of the table).

API Commands

This guide demonstrates the use of API commands.  Every command begins with 0xAA (170 Decimal) as a header byte, followed by the number of bytes in the Payload (the actual command).  Next, the actual command payload bytes are sent, followed by the 8-bit checksum.  Every command in this guide follows this sequence of operations.  To learn more about the API structure, please see the API Codec Quick Start Guide.  Since NCD controllers are “Speak when Spoken To” devices, they will respond with a API formatted response (when appropriate), which also begins with 0xAA (170 Decimal).  The Payload is what is responsible for controller operations.  The Payload should ALWAYS be “Wrapped” with a NCD API structure as described in the API Codec Quick Start Guide.

Before You Get Started…

Power and Hardware Setup

Before exploring this guide, it is critical to provide appropriate power to NCD ProXR Series controllers and any associated expansions.  NCD ProXR controllers require a 12V DC regulated power supply.  A switching power supply should always be used to properly regulate power to NCD controllers.  Unregulated supplies such as wall-wart type transformers can fluctuate voltage significantly.  These types of power supplies are not suitable for use with NCD controllers.  Be sure to always use a computer grade switching power supply to power NCD devices and expansions.  Please allow up to 100mA per relay as part of your power budget.  This may be excessive for some controllers as smaller relays may consume less than 50mA per relay channel; however, allowing for surge currents is considered best practice when possible.  Most ProXR series controllers consume less than 25mA standby current, but we recommend allowing for 100mA Standby power budget at 12VDC.  NCD controllers are shipped in a conductive static protection plastic bag.  Please remember, this bag is conductive, and placing the controller on top of this bag during initial testing can cause permanent damage to the controller.  Please place this controller on a non-conductive surface BEFORE powerup.

Fuses and Current Protection

NCD controllers are not fuse protected nor are they current protected.  Exceeding the current rating or short circuiting critical parts of the controller can cause damage to the controller or connected electronics.  We strongly recommend using NCD controllers along with current protection and/or fuse protection as necessary to prevent damage to the controller or connected devices.  Since every application is different, a power protection strategy that matches the installation application is strongly advised.

Application Limitations

Please remember that NCD devices are not suitable for use in applications that could endanger human life or property.  NCD devices are not certified for use in medical devices of any kind.  Relays have a limited lifespan and the eventual failure of a relay should never endanger people or property.  Please keep in mind that relays can fail in the “On” state whereby a relay cannot turn off.  It is also possible for relays to fail in the “Off” state whereby a relay cannot turn on.  Please be prepared for these types of failures.  If this is not acceptable, your application may require a custom manufactured certified solution.  Please remember that NCD devices, like all electronics, are subject to receiving Electromagnetic Interference.  Nearby lightning strikes, both direct or indirect, may cause failure or unintended operation.  Additionally, power disruptions, physical jarring, and other unforeseen events may also cause unintended operation.  While we have taken every reasonable precaution to prevent unintended operation, this is something that can never be 100% guaranteed.  Please plan for unintended operation as you implement the use of NCD controllers.

Expansion Controllers

Please note that it is critical for all expansion to be powered up along with the main controller simultaneously.  The main controller will attempt to turn all relays off upon power-up as a first order of operations.  This significantly reduces the chances of relay “glitching” on power-up.  Expansion controllers should NEVER be powered up after or independently of the main controller as the controller has no possible way of initializing a newly powered expansion.  All power and expansion ports must be connected prior to powerup and operation.  Expansion ports cannot be implemented or modified in any way while power is applied to the main controller.  Powering up any expansion controller AFTER the main controller is powered up will likely damage the main controller, expansion controller, or both.  The XR and UXP expansion ports actively send data to expansion controllers, even if they do not exist.  Sending data to an expansion that does not have power will likely cause serious damage.  In addition, expansion controllers that do not have a properly connected XR cable will cause unintended relay operation.  Powering a relay expansion independently of the main controller will also cause unintended relay operation.  It is absolutely critical to follow proper operation guidelines and to power-up the main controller along with all connected expansion controllers at the same time.

Base Station Quick Start Guide

The Base Station Quick Start Guide can also help you see commands in real-time as you click through the Base Station User-Interface.  This is hidden by default to help simplify the interface, be SURE to examine this short quick start guide to help get the most out of the user interface experience.

Relay Status Feedback

All NCD Relay Controllers will report the intended state of the relay as it is represented in the controller memory, which may not be the actual hardware state of the relay.  The hardware state of a relay cannot be monitored without current feedback from each relay, which is not supported in any of the existing generation of relay controllers.  In most applications, the memory state (or the intended relay state) is correct, but damaged relays, improperly powered expansion controllers, high-induction, or extreme EMI can cause a mismatch between the relay controller memory and actual on/off state of the relays.

Controlling Inductive Loads

NCD defines Inductive loads such as motors, solenoids, transformers, or any other device that causes motion or includes a magnetic coil of any kind.  These types of devices generate a magnetic field within the coil.  This magnetic field collapses when turned off.  The collapse of this magnetic field generates a voltage spike that flows back into the relay.  These inductive spikes can be severe and may need to be suppressed using capacitors.  Please review our guide on how to properly control inductive loads.