Sensor Controlled Relay 1-Channel 20-Amp with USB Interface
LRR120_USB
Sensor Controlled Relay
The LRR120_USB can be configured to will allow attached sensors to trigger relays at a predetermined setting. 0 to 5 volt sensors can be connected to the board which will convert the voltage to a numerical value between 0 and 255. You can set what value you want the relays to trigger! Trigger above, below or in between values. Set delays after the value has been reached (light stays on for 10 minutes after sensor activation). Options are limitless!USB Configuration
The TLR120_USB Sensor Controlled Relay uses a USB cable to connect to your computer to configure the board. Remember, once the board is configured, the computer is no longer needed. Making this the ideal choice for controlling relays using a sensor or contact closure!
Sensor Controlled Relay 1-Channel 20-Amp with USB Interface
LRR120_USB- OVERVIEW
- USB Interface
- Reactor Setup
- Board Features
- Power & More
- Relay Logic
- ACCESSORIES
- Data Sheets
Sensor Controlled Relay at a Glance
- 1 20-Amp Relay Installed
- Single Pole Double Throw (SPDT) Relay
- Normally Open 20-amps, Normally Closed 10-amps
- Wire Using 1/4" Quick Disconnect Terminal
- Temperature Rating -40° C to 85° C
- Not-Expandable - Onboard USB Interface Module
- Configure Board with USB Connection
- Plugs Directly into USB Port
- Configure Using Base Station - Configuration options
- 256 Different Trigger Points
- 8 Background Timers Available
- 4 Rotation Counters Available
- Configure Activation Sequences
Operates Without a Computer
Once configured the board will operate on it's own and no computer is needed!
Reactor Relay
USB Configuration
The LRR120_USB Reactor Controller must be configured using a computer and the included Base Station Software. Once configured, a Reactor will operate without a computer. By choosing a USB version you will connect your computer to your controller via a USB cable. This is the easiest and most popular way to connect to the Reactor Board. At any time, a computer may monitor the Reactor, Trigger Events, Activate Relays, or Change Configuration settings. A computer can take over a Reactor or a Reactor can operate autonomously (without a computer).Inputs Monitored
Once a Reactor is configured, the Reactor monitors inputs. When inputs reach user-defined limits, relays can turn on or off. Reactors allow much more than simple relay control. Reactor inputs can trigger timers and rotations. A timer allows a relay to activate over a duration of time. A rotation is a simple counter, in which relays can be assigned to each "count". This allows powerful functions such as relay activation sequencing, flashing, and stepping. Event Piping allows timers and rotations to trigger other timers and rotations. This is very powerful for setting up complex relay activation sequences.Mounts as a COM Port
This ProXR series controller connects to the USB port of your computer and will mount as a COM port on your PC. USB Drivers will most likely be needed and can be found in the resources section to the right and will also be available in the Base Station Software. Windows 7 & 8 users will automatically download and install the necessary drivers.ZUSB Modules
This board is equipped with a ZUSB Module. The ZUSB communications module adds USB communications to the board. The ZUSB module is powered from the USB port of your computer and includes a 6' USB Cable. The board itself will require 12 volts of power and can be hard wired or you can purchase a "wall wart" type Power Supply at checkout.
8 Inputs Available
Reactor Inputs play a vital role in the use of a Reactor controller. Analog inputs are simply inputs that are sensitive to voltages. Analog Inputs are capable of reading switches and sensors operating in the 0 to 5VDC range. Once configured, the Reactor CPU is constantly monitoring external sensors using 8 analog inputs that can read switches, resistance changes, or voltages from 0 to 5VDC. Inputs can be configured to trigger relays, relay timers and relay activation sequences.Input Voltage Changes
Analog Inputs are very special in that they are sensitive to voltage changes. In the case of a Reactor controller, analog inputs have an 8-bit resolution, meaning the voltage input (from 0 to 5VDC) is interpreted as a value from 0 to 255.
- For Example
- A voltage input of 0 Volts is interpreted as a value of 0
- A voltage input of 2.5 Volts is interpreted as a value of 128
- A voltage input of 5 Volts is interpreted as a value of 255
So if you divide 5 Volts by 256 possible steps (0-255 for 8-Bit resolution), the Reactor controller is sensitive to voltage changes as small as 0.0195 Volts. A Reactor controller has 8 inputs. Each input is capable of reading a separate voltage from 0 to 5 VDC, provided all voltages can share a common ground. You configure exactly what value you want the board to trigger the relay or start a sequence or delay!
Who’s Qualified to Use the Reactor Series?
Some computer skills required. The Reactor Relays do not require programming, simply configure the device with the included Base Station Software. While programming is not required and simple functions can be done rather easily with basic computer skills, complex events can be configured which will require some understanding and patience.Induction Capacitors
Perhaps the most overlooked aspect of relay control is proper handling of inductive loads. Inductive loads can best be defined as anything with a magnetic coil, such as a motor, solenoid, or a transformer. Controlling a inductive load using this relay controller requires the use of induction suppression capacitors. The purpose of this capacitor is to absorb the high voltages generated by inductive loads, blocking them from the contacts of the relay. Without this capacitor, the lifespan of the relay will be greatly reduced. Induction can be so severe that it electrically interferes with the microprocessor logic of our controllers, causing relay banks to shut themselves down unexpectedly. In the case of USB devices, customers may experience loss of communications until the device is reconnected to the USB port. Capacitors that we offer are available at checkout, for more information view our Induction Suppression Video.
Base Station Configuration
Reactor boards are configured using the Free Base Station Software. The GUI interface makes it easy to configure simple automation tasks with a point and click interface! Download Base Station
Base Station Reactor Configuration
Base Station Software
Base Station will assist you in learning how this device functions and is the ultimate reference tool for configuring, testing and controlling this device. Base Station software supports every feature of this device - no other controller manufacturer even comes close to offering this type of software. Base Station works by communicating with your controller to identify the model and provides the appropriate graphical user interface for setting up and testing the identified device. All Reactor configurations will be made through Base Station and an overview will be discussed below. To help you get started and learn this controller Quick Start Guides are available for just about every feature. As you discover a feature in Base Station a link is provided where you can easily download the Quick Start Guide. Download Base StationeConfigure Each Input
The Reactor Relay allows users to define the activation of a relay or an event based on the voltage readings of the analog inputs. An input can trigger a relay directly or an input can trigger an
event, such as a timer. If an input triggers a relay, the relay may turn on. If an input triggers a timer event, a timer may be started,
but a relay may or may not be turned on based on how you have configured the controller (the time delay may be before the relay triggers). Triggering an event does not mean you are triggering a relay, it just means you are triggering an internal function. Relays may be associated
with this internal function to achieve a large number of possible operations.
Using Input Values

Reading from Left to right, the settings above indicate Input 1 will trigger a relay when Analog Input 1 is above 200. We have defined that a relay will turn on when the input level is defined by a value of 200.

In the above example, a relay is triggered when an analog input is inside a set range between 100 and 202. By defining two limits, you can further narrow the parameters for the activation of a relay. The limits can also be assigned to set the relay to be activated outside two set limits.
Output Configuration
The configuration software makes it easy to configure each relay. Relays or multiple relays can be can be assigned to each input.
There are many ways to directly control a relay from an input. Relays 1-5 in the below example shows how inputs can turn relays on, off, toggle relay state, set the relay to match the state of the input, or set the relay to NOT equal the state of a input.
In the example below, Relay 6 is controlled by Timer 1. In other words, if Timer 1 is active, the relay will stay ON. Otherwise, the relay will turn off. This is a great way to activate a light for a given period of time. If you are interested in Time Delay Relay, timers will be discussed on our Time Delay Relay Page.
Complex Automation through Experimentation
Dont be afraid to experiment with Reactor! Some complex automation can be achieved by experimenting with Reactor settings. Of course Reactor is capable of triggering relays and it can also trigger events. Relays can be associated with events, allowing you to play with all kinds of complex timing and counting settings. Events greatly expand the pallet of functionality available to Reactor.Computer Controlled Relays
Software developers who need remote access to a Reactor controller will find themselves at home.  The Reactor supports a very powerful computer-based command set, so it is possible for a computer to operate the relays and read sensor inputs.  The computer can over-ride the Reactor decision logic, trigger events, and return control of the relays back to the Reactor Logic. Configuration settings are stored in files that can be loaded into other Reactor controllers.Many More Options
We have just touched on the many ways the Reactor board can be configured. The applications that this board can be use in are extensive. For a more detailed look at the configuration and setup you can look at the Reactor Series Quick Start Guide.Reactor Video
Attention: 0 - 5 Volt DC Input Only
Please Note: Analog inputs can accept voltages from 0 to 5VDC ONLY. Higher voltages and negative voltages will damage the Reactor controller. Improper use of these inputs can cause irreparable damage to the board.
Reactor Board Features
Reactor Relay
In this tab we'll take a look at the Reactor board design itself. The Reactor series controllers are machine manufactured for a highly accurate and reliable design. Fully tested before they leave the production facility each Reactor controller is ready to stand up to rigorous demands from heat, cold or vibration. The best test of all is the numerous boards in the field from customers all over the world in all sorts of conditions. Take it from us, these controllers will hold up!Essential Power Requirements
Applying Good clean power to the board is essential for the operation of the board. Not only for the switching of the relays but the firmware that processes the commands. Without good steady clean power from a regulated power supply the board simply will not function correctly. All boards on the site require 12 VDC power. The PWR12 US power supply is a 120VAC to 12VDC 1.25A 60Hz regulated power supply and it plugs into the barrel connector on the board. The output connector is a 2.1mm I.D. x 5.5mm O.D. x 9.5mm Female R/A barrel connector. We also carry an international power supply with interchangeable adapters for international customers. Learn More
Amperage Rating
The 20-Amp relay is reated for 20-amps on the Normally Open connection and rated for 10-amps on the Normally Closed connection. Please keep this in mind when wiring to the Normally Closed side it is only rated for 10-amps.20-Amp SPDT Relay Installed
This device has SPDT relays installed. SPDT Single Pole Double Throw Relays have three connections - Common, Normally Open, and Normally Closed. When the relay is off, the common is connected to the normally closed connection of the relay. When the relay coil is energized, the Common swings over to the Normally Open Connection of the Relay. You can wire the device you are switching to either the Normally Open or the Normally Closed position.
The Common (COM) is the
moving part of the relay that comes in contact with the Normally Open (NO) when the coil to the relay is energized. Wiring is done directly to the Relay terminals using a common 1/4" quick disconnect terminal. To the right is a picture of the connector that will connect to the relay.
2-Million Cycles
Reactor series boardss are designed for long life, you should expect to get years of service from your controller and literally 2-million cycles from the relays on board. With a 5-year warranty and a money back guarantee you have nothing to loose!This Board is RoHS Compliant
This board is led free and RoHS Compliant. If your requirements are for RoHS compliant parts this board is manufactured with RoHS compliant led free parts and solder.
Not Expandable
The Reactor Series controllers are not expandable.Break-A-Way Tabs for a Smaller Design
The Reactor relays have a great feature where space is a premium - Break-A-Way Tabs. The Break-A-Way Tabs allow most boards to fit in an optional undrilled plastic enclosure. Snap off the Break-A-Way Tabs and you have a controller with a smaller profile when you need to fit in a tight space.30-Day Warranty/Money Back Guarantee
Reactor series controllers are guaranteed against manufacturing and functionality defects for a full 30 days! Not to mention a 30-day money back guarantee! If for any reason you are not happy with a relay purchased from Relay Pros, simply return it within 30 days and we will give you your money back! Controllers that are damaged by our customers will not of course be warranted under any circumstances.Shipping
The boards sold are brand new units shipped from our office conveniently located in Missouri. These boards are completely tested before they are released for shipping With so many boards on our site it is impossible to stock boards, please allow two to three days production time for your order to ship. If you have any questions please feel free to call our office at 800-960-4287 or e-mail us at sales@relaypros.com.
Sensor Control Is Here!
Trigger relays with a sensor with and configure with included Base Station software. Here's a lists of great features:- User Friendly Software
- Point & Click Interface - No Programming Knowledge Required
- Override Sensor When Computer is Connected to Board
- Read Sensor Levels in Base Station
- Read Status of Relays in Base Station
- User Friendly Board Design
- 8 Analog Sensor Inputs Available (0 to 5 Volt Only)
- Break-A-Way Tabs lets you decide the board's size
- Direct relay connections make connecting to the relays easy
Building a Power Budget
The operating range of the board is between 9 & 14 VDC, any power outside this range and the board can become unreliable. Use the tables below to build a power budget for the board you have based on the module you have and the anticipated time the relay will be active.
Power & More
20/30 Amp Relay Board Specifications
This table covers all NCD boards with 20 or 30 amp relays installed. All ratings assume 12VDC operation at 70°F (21°C). Please note that most ratings are estimated and may be subject to periodic revision. Some ratings represent stock controller settings without performance enhancement optimizations. The estimated processing time can be impacted by background services and choice of commands. Standby power consumption assume no communications module is installed and no relays are active on the controller. Please add the power consumption of the activated relays and communications module to obtain a better estimation of power consumption.| 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 |
Communication Module Specifications
This table covers all NCD Communication Modules. While NCD communication modules operate at 3.3VDC, the ratings below highlight the effect they will have on the master controller operating at 12VDC at 70°F (21°C). Maximum ratings should be used for power budget planning purposes and may reflect short term absolute maximum peak current consumption. Some ratings are estimated and subject to periodic revision.| 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 |
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| 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 |
AD8 Analog Input Usage Notice
Analog Inputs should not have a voltage present when powered down. Use a 220 Ohm current limiting resistor on each input to prevent damage to the controller if voltage will be present on the analog input when this controller is powered down. Do not exceed 0 to 5VDC on any analog input or the on-board CPU will be damaged. Most analog inputs include a 10K Pull Up/Down resistor to help keep the inputs quiet when not in use. This 10K resistor may slightly bias the readings of some sensors.LRR120_USB Accessories
Power Supply Available
The PWR12 is regulated power supply providing clean power necessary for
the performance of these boards. The PWR12 US power supply is a 120VAC to 12VDC 1.25A 60Hz regulated
power supply and it plugs into the barrel connector on the board. The output connector is a 2.1mm I.D. x 5.5mm
O.D. x 9.5mm R/A barrel connector.
Click Here for More
Enclosure Available
The TFL Enclosure is an undrilled, non-waterproof enclosure and is available at checkout for this controller.Spec Sheet and Drawings:
TFL Spec Sheet
CAD Drawing: TFL CAD Drawing
3D Model: TFL_3D
Induction Suppression
Controlling
an inductive load using our relay controllers requires the use of induction suppression capacitors. The purpose of this capacitor
is to absorb the high voltages generated by inductive loads, blocking them from the contacts of the relay. Without this capacitor,
the lifespan of the relay will be greatly reduced. Induction can be so severe that it electrically interferes with the microprocessor
logic of our controllers, causing relay banks to shut themselves down unexpectedly.
Click Here for More
Base Station
Reactor boards are configured
using Base Station Software (a free download). Using a point-and-click interface for configuration means you can accomplish automation tasks in minutes.
There are no programming languages to learn. Click for more on Base Station.
What Is Relay Logic?
Relay logic uses relays wired in specific configurations to achieve predictable switching behavior. In practical terms, it's the process of arranging relays so they perform the logical control functions your application requires.
Get a printout of this page
Relay Logic
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.
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.
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 SPST examples shown on this page apply to these relays as long as the example does not require a Normally Closed terminal.
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.
Relay Grouping in the ProXR Command Set lets you combine individual relays to function like a DPDT relay using separate channels. This is ideal when you need to control multiple relays simultaneously or exceed the 5-Amp switching limit of our standard DPDT relays.
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.
Example 2 - Simple On/Off (Using NC Contact)
This wiring method keeps the device 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.
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
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 close 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.
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)
- For example:
- Relay 1 = night/day sensor
- Relay 2 = motion sensor
- Relay 3 = manual override (local switch)
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.
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
- 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.
MirC/MirX Users: Wire two contact closure inputs into the sender board - either input can trigger the receiver relay to control the light.
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
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 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
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.





