MirC Board Features

"Reliable Remote Relay Control - No Matter How You Connect"

Switch From One Location - Control Another

MirC boards come in married pairs, letting you control a relay using a simple dry contact - no voltage input. That contact can come from a switch, a sensor, another relay - anything that can close a dry contact circuit.

When the input contact is closed, the relay stays energized. When the contact opens, the relay turns off. So the relay will follow either momentary or toggle-style inputs depending on what you wire into it.

Each MirC pair is built to handle tough environments - heat, cold, vibration - you name it. These boards are workhorses, and they're designed to stay that way.

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Relay Outputs

MirC relays act as dry-contact switches. They don't output voltage - they simply open or close the circuit feeding your device.

Each relay is rated for 240 VAC or 24 VDC. For full electrical specifications and relay models, check out the Data Sheets tab above.

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Status of Remote Relays

Both boards include LEDs that show the real-time status of the relay on the remote board. Thanks to true 2-way wireless communication, status indicators stay accurate.

If communication drops, the status LED turns off so you know immediately. Every MirC controller also includes a Busy/Ready LED:

• A flashing Busy LED means the remote board received and accepted your input.
• If the Busy LED doesn't flash, the other board is out of range or unable to respond.

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SPDT Relay Installed

SPDT (Single Pole Double Throw) relays include three terminals: Common (COM), Normally Open (NO), and Normally Closed (NC)

• When the relay is off, COM is connected to NC.
• When the relay is energized, COM switches to NO.

Your load can be wired to either the NO or NC terminal depending on whether you want the device to turn on when the relay activates or when it releases. Examples of wiring methods can be found in the gray Relay Logic tab.

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2 Million+ Cycles

ProXR relays are built for longevity - expect years of reliable operation and millions of mechanical cycles. Every board ships with a 5-year warranty and 30-day money-back guarantee.

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Break-A-Way Tabs for a Smaller Design

Need a smaller footprint? The MirC PCB includes Break-A-Way Tabs, allowing the board to fit into optional undrilled enclosures or tight-space installations.

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Essential Power Requirements

Clean, regulated power is critical.
A stable 12VDC supply ensures both the relay coils and onboard firmware operate correctly. Unstable or noisy power can cause improper switching or communication issues.
We recommend the PWR12-US (120VAC → 12VDC @ 1.25A) or our international supply with interchangeable adapters.
Learn More

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RoHS Compliant & Lead-Free

All MirC controllers are built with RoHS-compliant components and lead-free solder.

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5-Yeary Warranty & Guarantee

Every MirC controller is covered by:

• 5-Year Functional Warranty
• 30-Day Money-Back Guarantee

If you're not satisfied, send it back for a refund within 30 days. (Damage caused after delivery isn't covered.)

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Shipping

All boards ship directly from our Missouri facility. Each unit is built and tested at the time of order - please allow 3 - 5 days for production. We ship primarily through UPS, but we're happy to use FedEx or DHL for international orders when you provide your account number. Questions? Call us at 800-960-4287 or email sales@relaypros.com.

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Induction Suppression

One of the most important parts of relay control - yet the most commonly overlooked - is inductive load protection.

Anything with a magnetic coil (motors, solenoids, transformers, etc.) generates high-voltage "kickback" when switched. Without a suppression capacitor, that spike can:

• Shorten relay lifespan
• Cause electrical noise that disrupts the microcontroller
• Trigger unexpected shutdowns
• Require power cycling to restore communication

Adding an induction suppression capacitor protects your relay contacts and keeps everything running smoothly. Capacitors are available at checkout, and our Induction Suppression Page has wiring diagrams and more details.

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Contact Closure Relay Is Here!

A more streamlined manufacturing process brings a more durable, reliable and better relay board to the market. Here's a lists of great features:

User Friendly Board Design


• Single Pole Double Throw Relays Installed
    - Wire to Normally Open or Normally Closed Position
    - 12 Guage Solid Core Wire Capacity
• Screw Terminal Contact Closure and Relay Connections
• Break-A-Way Tabs Lets you Decide the Board's Size
• Temperature Rating -40° C to 85° C
• RoHS Compliant

MirC Features

• Control Relay from a Dry Contact (No Voltage)
• Inputs on Sender Board Control Relays on Receiver Board
• Sender Board Displays Status of Remote Relays

MCNET / MXNET Setup

"A quick setup gets you rock-solid network control"

Before You Start (Requirements)

These boards communicate over your Local Area Network - not the public internet. Both boards must be on the same LAN and assigned a static IP address. They do not work if the boards are plugged directly into each other or directly into a computer - they must be connected through a LAN.

We strongly recommend assigning IPs outside your router's DHCP range to avoid conflicts.

If this installation is part of an IT-managed network, share this guide with your network administrator before beginning.

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Static IP Required

During configuration, you'll designate one board as the server and the other as the client. Each board also requires a static IP address. If the boards are left on DHCP and the router power cycles, the router may assign new IP addresses, which means the client board may no longer know where to find the server board - communication stops cold. Assigning static IPs prevents that.

We recommend assigning addresses outside your router's DHCP range. One board will act as the server while the other acts as the client, connected through a TCP socket. You can choose any port number you like - in our setup we used port 2101. This can matter if the boards are on separate subnets.

Relay Pros / NCD can't provide support for complex network setups - for that level of configuration, your network admin is the one to loop in.

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Windown Configuration

Setup requires the free configuration software and a Windows computer connected to the same network as the boards.

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Managed Network Required for Setup

Out of the box, both boards are set to DHCP mode. That means configuration must begin on a managed network.

Once setup is complete, the boards may be installed on an unmanaged network, no problem.

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Configuration

Initial setup

• Download and install the NCD5500 NCD 5500 Configuration Software.
• onnect standard Ethernet cables to both boards, attach them to the network, and power them with a regulated 12VDC supply.
• Open the NCD5500 Configuration software.
• Click Search until both boards appear in the list.
  Each board will be identified by its MAC address, which is also printed on the Ethernet module - helpful for telling them apart.

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First board Configuration (Server)

• Select one of the boards to open its settings.
  All steps are under Basic Settings - nothing needed in Advanced Settings.
• Set the baud rate to 57600.
• Under Network Settings, switch to Use the following IP address.
• Assign a static IP address and enter Subnet Mask, Gateway, and DNS Server as required for your network.
• Under Connection, set Work As to TCP Server.
• Enter a Local Port (any port except 80). We used 2101 in our testing.
• Click Apply Settings.

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Second Board Configuration (Client)

• Select the second board to open its settings.
• Set the baud rate to 57600.
• Switch Network Settings to Use the following IP address.
• Assign a different static IP address, and enter Subnet Mask, Gateway, and DNS Server.
• Under Connection, set Work As to TCP Client.
  (Local Port is not required here.)
• Enter the Server Board's IP address into the Remote Host field.
• Enter the Server's Local Port number in the Port field.
• Click Apply Settings.

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Final Testing

Once settings are applied on both boards, communication should establish automatically.

You can verify a successful TCP connection two ways:

• The red LED on the Ethernet module (next to the metal jack) will be solid on.
• The Busy/Ready LEDs on the boards will flash periodically, confirming communication.

Close the dry-contact inputs, and you should hear the relays on the remote unit switch on and off.

Power & More

"Reliable Power = Reliable Switching"

20/30 Amp Board Performance Ratings

This tab brings together the essential performance ratings you'll want to know for NCD 20/30 Amp Relay Controllers and their supported communication modules. You'll find practical electrical requirements, power consumption estimates, operating limits, relay timing details, and more-all based on typical 12VDC operation at 70°F (21°C). Think of it as a reliable snapshot of how our hardware behaves under real-world conditions. Because every installation is unique, some values are estimates and may evolve as designs and testing continue. Use this information as a planning tool to help you choose the right controller, build an accurate power budget, and understand the capabilities built into every NCD 20/30 Amp relay board.

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Powering from a Battery or Solar Panel?

NCD relay controllers are well-suited for battery-powered and solar-charged applications when operated within the recommended 10 - 15VDC range. This makes them ideal for remote, mobile, and off-grid installations using common 12V battery systems with solar charging. The power consumption data on this page helps you estimate runtime, size your battery, and avoid over-discharge. Staying within the voltage limits ensures stable, reliable operation in long-term battery and solar-powered setups.

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SPDT Relay Specs

Specs of NCD SPDT Relay Boards	Minimum	Nominal	Maximum	Notes
Operational Voltages	10VDC	12VDC	15VDC
Standby Power Consumption	35mA	100mA	200mA	No Active Relays, No Com Module
Relay Power Consumption	28mA	35mA	60mA	Consumption of Each Activated Relay
Operational Temperature Range	-40°F (-40°C)	70°F (21°C)	185°F (85°C)	Theoretical Component Limits Shown
Storage Temperature Range	-67°F (-55°C)	70°F (21°C)	185°F (85°C)	Theoretical Component Limits Shown
Operational Ambient Air Humidity	0%	50%	70%	Non-Condensing Humidity Values Shown
Relay Activation Time			15ms	Needs Further Validation
Relay Deactivation Time			10mS	Needs Further Validation
Operational Life Mechanical	10,000,000			Component Operation Rating
Operational Life Electrical	100,000			Component Rating at Maximum Load

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Communication Modules

Communication Module Specifications

This table provides a quick, clear overview of all NCD Communication Modules. While each module operates at 3.3VDC, the values shown here reflect the impact on a 12VDC master controller at 70°F (21°C). Use the maximum ratings for power-budget planning - they represent short-term peak consumption and may include estimated values that are updated as modules evolve.

Communication Module Power Consumption

Specs of NCD Communication Modules	Minimum	Nominal	Maximum	Notes
Operational Temperature Range	-40°F (-40°C)	70°F (21°C)	185°F (85°C)	Theoretical Component Limits Shown
Storage Temperature Range	-67°F (-55°C)	70°F (21°C)	185°F (85°C)	Theoretical Component Limits Shown
Operational Ambient Air Humidity	0%	50%	70%	Non-Condensing Humidity Values Shown
USB Module Power Consumption	N/A	N/A	N/A	USB Modules are Powered by the USB Port Do Not Consume Device Current
RS-232 Module Power Consumption		10mA	20mA
Ethernet Module Power Consumption	58mA	82mA	100mA
WiFi Bluetooth USB Module Power Consumption	37mA	50mA	100mA	Up to 300 Foot Indoor Wireless Range, Unobstructed. Up to 50 Foot Range Through Walls
900MHz Wireless Module Power Consumption	13mA	30mA	50mA	Up to 1,000 Foot Indoor Wireless Range, up to 2 Mile Outdoor Wireless Range using Included Antennas. Up to 28 Miles Outdoor Wireless Range using High-Gain Antennas.
KFX Wireless Key Fob	11mA	15mA	25mA	Up to 200 Feet Outdoor Wireless Range using 1, 2, 3, 4, or 5 Button Key Fobs. Up to 700 Feet Outdoor Wireless Range using 8-Button Remotes

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A/D Inputs

AD8 Analog Input Usage Notice

Analog inputs should never have voltage applied when the controller is powered down. If your application requires voltage to remain on an input, add a 220-ohm current-limiting resistor to each channel to protect the controller from damage. Keep all analog inputs within the 0 - 5VDC range - exceeding this limit can permanently damage the on-board CPU. Most inputs include a 10K pull-up or pull-down resistor to keep the line stable when unused, but note that this resistor may introduce a slight bias in readings for certain sensors.

Accessories

Relay Logic

"Using a light as an example load, let's wire to the board"

Relay Wiring Samples

This page provides simple examples showing how to wire a single relay - or multiple relays - for common switching applications. We use a light as the example load, but you can substitute a gate controller, security panel input, dry contact device, motor trigger, or most other switched loads. These wiring samples demonstrate different ways to connect relays to achieve the switching behavior you need.

Get a printout of this page

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Relay Types

SPDT Relay

SPDT (Single Pole Double Throw) relays include three terminals: Common (COM), Normally Open (NO), and Normally Closed (NC).

• When the relay is off, COM is connected to NC.
• When the relay is energized, COM switches to NO.

Your load can be wired to either the NO or NC terminal depending on whether you want the device to turn on when the relay activates or when it releases. Examples below demonstrate both wiring methods. The SPDT relays offered on this site are 5-Amp, 10-Amp and 20-Amp models.

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SPST Relay

SPST (Single Pole Single Throw) relays provide two terminals: Common (COM) and Normally Open (NO).

When the relay coil is energized, COM connects to NO to power the load. The only SPST relays offered on this site are our 30-Amp models. All SPDT examples shown on this page apply to these relays as long as the example does not require a Normally Closed terminal.

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DPDT Relay

A DPDT (Double Pole Double Throw) relay contains two SPDT switches that operate together.

• Each side includes its own COM, NO, and NC terminals.
• Both internal switches change state at the same time.

This allows you to control two independent circuits with one relay. Wiring for each side of a DPDT relay follows the same rules as an SPDT relay, so the examples on this page apply directly. We offer the DPDT relays in 1-Amp, 3-Amp and 5-Amp models on ProXR boards starting at 8 relays.

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Relay Logic Examples

Example 1 - Simple Off/On Control

This example shows the most basic way to use a relay to switch a device such as a light. When the relay energizes, its NO (Normally Open) contact closes to COM (Common), completing the circuit and turning the light on.

Only a single power wire is switched in this setup, making it the simplest method for controlling a light - or any device - using a relay.

Use this example for switching a light or any device you want to power only when the relay is on.

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Example 2 - Simple On/Off (Using NC Contact)

This wiring method keeps the light on by default. The relay switches a single power wire through the COM (Common) and NC (Normally Closed) terminals.
When the relay is not energized, the NC contact is closed to COM and the light remains on.
When the relay energizes, the NC contact opens, interrupting power and turning the light off.

This approach is ideal for devices that stay on most of the time, reducing relay wear since it doesn't need to remain energized to keep the device powered. It's also a useful method for power-cycling equipment - energizing the relay momentarily will turn the device off.

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Example 3 - AND Logic Using Two Relays

This example shows how two relays can work together so a light turns on only when both relays are energized. This creates an AND Logic condition:
Relay 1 AND Relay 2 must be on for the light to receive power.

A single power wire is switched, but it must pass through both relay contacts before reaching the light. This setup is ideal when two conditions must be met at the same time - such as requiring input from multiple sensors or system parameters.

MirC/MirX Users: This wiring requires two contact closure inputs on the sender board before the receiver's relay activates. Use this approach when two independent outputs must close before turning on the light.

For example, a light could turn on only when:
• A light sensor detects it's dark AND
• A motion sensor detects activity in the room

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Example 4 - AND Logic Using Three Relays

This example expands on the previous AND Logic concept. Here, the light will turn on only when all three relays are energized:

Relay 1 AND Relay 2 AND Relay 3 must be on for power to reach the light.

A single power wire is routed through all three relay contacts. Wiring from the NO (Normally Open) of Relay 1 to the COM (Common) of Relay 2, then from the NO of Relay 2 to the COM of Relay 3, creates a series path that requires every relay to energize before the light can activate.

This method can be scaled easily - just continue wiring NO of each relay to the COM of the next relay. Add as many relays as needed to meet your logic or safety requirements.

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Example 5 - AND/OR Logic with Override

This example demonstrates a combined AND/OR logic setup. The light will turn on when:

• Relay 1 AND Relay 2 are both energized
  OR
Relay 3 is energized (override)

This wiring is useful when you need a normal logic condition plus a manual or automatic override option.

For example:
• Relay 1 = night/day sensor
• Relay 2 = motion sensor
• Relay 3 = manual override (local switch)

If it's dark and the motion sensor activates, Relays 1 and 2 energize to turn on the light. But if you want to control the light manually - regardless of sensor conditions - Relay 3 can override the logic and activate the light on its own.

A/D Board Users: The Relay Activator function on any A/D board or ProXR Lite board lets you connect a button or switch to any A/D input. This input can then control the override relay, giving you a convenient local button to manually override the first two relays.

MirC/MirX Users: Add a manual button or switch to trigger the third relay when you need direct control instead of sensor-driven control.

Reactor Users: A local button or switch can be wired to the third relay input to provide a manual override for sensor-based logic.

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Example 6 - OR Logic (Either Relay Activates)

This example demonstrates OR Logic - the light will turn on when either relay is energized. Only one power wire is switched, but it can pass through Relay 1 or Relay 2 to reach the light.

• If Relay 1 activates, the light turns on
• If Relay 2 activates, the light turns on
• If both activate, the light remains on

This setup is ideal when two independent sources should be able to control the same device. Common uses include:

• A timer controlling one relay, with a manual or secondary control for the other.
• Two sensors where either condition (motion detected or low light, for example) should activate the light.

A/D Board Users: The Relay Activator function on any A/D board or ProXR Lite board lets you connect a button or switch to any A/D input. This input can then be used as a manual control of the relay.

MirC/MirX Users: Wire two contact closure inputs into the sender board - either input can trigger the receiver relay to control the light.

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Example 7 - 3-Way Switch (Relay-Based 3-Way Control)

This example shows how to create a 3-way light switch setup using relays. A traditional 3-way circuit allows two switches to control the same light from different locations. In this wiring sample, each physical switch is replaced by a relay - but the operation is the same.

Only one power wire is switched, and the relays toggle the light depending on their current state.

• Activating either relay will toggle the light
• Activating both relays at the same time has the same effect as flipping both switches at once

This wiring method is especially useful because you can replace one of the relays with a physical light switch, giving you both computer control and manual control of the same light. When used correctly, this becomes one of the most flexible and powerful diagrams on the page.

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Example 8 - DC Motor Direction Control

This example demonstrates how to control the direction of a DC motor using two relays. By changing how the motor's leads connect to power, you can run the motor forward, reverse, or place it in a brake state. Braking is achieved by tying both motor terminals to the same power connection, which stops rotation through Faraday's Law.

Relay Operation Summary

• Relay 1 Off / Relay 2 Off → Motor Brake to +
• Relay 1 On / Relay 2 Off → Motor Forward
• Relay 1 Off / Relay 2 On → Motor Reverse
• Relay 1 On / Relay 2 On → Motor Brake to -

The capacitors shown are optional for small motors, but may be required in some situations:

• The induction suppression capacitor prevents the relay from shutting off due to motor back-EMF
• The 0.1µF filter capacitor reduces electrical noise, especially useful when powering sensitive electronics such as radios or amplifiers.

Capacitor Placement
• Place the induction suppression capacitor near the relays
• Place the filter capacitor near the motor
• Additional capacitors may be needed for certain motors

Important Note on Inductive Loads
Motors draw significantly more current at startup than during continuous operation - often 2-3 times their rated running current. For example, a motor rated at 5A (125VAC) may require 10-15A to begin turning. Always select a relay that exceeds the motor's initial inrush current, not just its running current. In this case, a 20-30A relay provides optimal performance and longevity.

Data Sheets & Quick Start Guides

Below are the Data Sheets Quick Start Guides for this board.  These are the guides that will help you communicate and configure this board.