MirX Wired Contact Closure

"No Signal No Network Wire Is the Right Answer!"

When Wireless Isn't an Option

The MIRXR430_ZRS is sold as a pair of identical boards. Each board includes both contact closure input and onboard relay - the inputs on one board control the relays on the other. This creates a simple and flexible way to control devices in both directions between two locations using a wired connection.

Communication between the boards is handled over a three-wire connection, making this a straightforward solution when reliability matters most.

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Go Where Wireless Won't Reach

Wired MirX controllers are built for environments where wireless signals struggle or fail completely:

• Through thick masonry or concrete walls
• Around steel structures or equipment
• In underground installations
• In areas with heavy RF interference
• Where security requirements prohibit wireless communication

When wireless can't make the trip, a wire gets it there every time.

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ZRS Communication Modules

Each board includes a ZRS module, connected using a simple screw terminal interface. The two modules are linked using a three-wire connection.

For best performance, use quality cable such as twisted pair (Cat5 or Cat6). The system supports distances up to 1000 feet (304 m) between controllers.

Each board is powered independently using 12 VDC, either hardwired or with an optional plug-in power supply.

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Status of Remote Relays

Both boards include LEDs that display the status of the remote relay using two-way communication over the wired link.

• If communication is active, status LEDs reflect real-time relay state
• If communication is lost, the LED turns off
• Ihe Busy/Ready LED flashes to confirm successful signal transmission

If the Busy LED stops flashing, it indicates a communication issue between the boards.

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Order of Operation

1. A contact closure is detected on one of the boards
2. The signal is transmitted over the wired connection
3. The other board switches the relay ON or OFF
4. A confirmation signal is sent back
5. The Busy LED flashes to confirm successful communication

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What Happens When Communication is Lost

If a relay is energized and the connection drops between the two boards, you get to choose what happens next:

• The relay can stay energized until communication returns (Beacon Mode)
or
• The relay can turn off automatically (Smart Mode)

Just set the jumper for Beacon or Smart mode depending on how you want the system to behave.

MirX Board Features

"Reliable Two-Way Relay Control - No Matter How You Connect"

Switch From One Location - Control Another

MirX 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 MirX 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

MirX 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 MirX 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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SPST Relay Installed

This MirX model is equipped with an SPST (Single Pole, Single Throw) relay. SPST relays do one thing and do it well - they simply connect or disconnect two wires.

When the relay is energized, the Common (COM) contact connects to the Normally Open (NO) contact, completing the circuit. When the relay is off, the circuit is open.

Wiring is done to the Common and Normally Open positions directly to the relay using standard 1/4" quick-disconnect terminals. (A matching connector is shown at right.)

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2 Million+ Cycles

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

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5-Yeary Warranty & Guarantee

Every MirX 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 Single Throw Relays Installed
    - Wire to the Normally Open Position
• Wire Directly to the Relay Using 1/4" Quick Disconnect Terminal
• Break-A-Way Tabs Lets you Decide the Board's Size
• Temperature Rating -40° C to 85° C
• RoHS Compliant

MirX Features

• Control Relay From a Dry Contact (No Voltage)
• Inputs and Relays on Both Boards
• Inputs Control Relays on Opposite Board
• Each Board Displays Status of Remote Relays

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.

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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.