Onefinity Redline Optical Limit Switch Wiring for a MASSO Conversion

Article type: Machine-Specific Research
Machine family: Onefinity with Redline controller
Sensor manufacturer: F&C Sensing Technology
Sensor model: FC-SPX306
Output type: NPN
Operating voltage: 5–24 VDC

Research notice: This article documents hardware inspected and tested by PwnCNC while researching Onefinity-specific controller conversions. Manufacturers may change sensors, connectors, wiring, or other components without notice. Always confirm that your hardware matches the examples shown before making wiring changes.

Overview

Onefinity machines equipped with the Redline controller use an optical limit switch that operates from the controller’s 5 VDC sensor supply.

During our conversion-kit research, PwnCNC identified the sensor as an F&C FC-SPX306 NPN optical sensor. The sensor supports an operating range of 5–24 VDC, allowing it to be powered by the 24 VDC sensor supply used in our MASSO conversion-kit wiring.

This means the original optical sensors may be reused during a MASSO conversion rather than replaced, provided the sensors and wiring match the hardware documented in this article.

Identified Sensor

The model number printed on the sensor is FC-SPX306.

Specification	Identification
Manufacturer	F&C Sensing Technology
Model	FC-SPX306
Sensor type	Slot-style optical/photoelectric sensor
Detection method	Opposed-beam optical detection
Output type	NPN
Operating voltage	5–24 VDC
Factory Redline supply	5 VDC
PwnCNC conversion-kit supply	24 VDC

The manufacturer’s published specifications for the F&C FC-SPX306 confirm its 5–24 VDC operating range.

F&C FC-SPX306 optical limit switch, Onefinity cable and factory mounting hardware.

Verified Wire Functions

Opening the sensor allowed us to trace the conductors and verify how the Redline harness uses them.

Wire color	Function	Redline configuration	PwnCNC MASSO conversion
Brown	Positive sensor supply	+5 VDC	+24 VDC
Blue	DC common / 0 V	0 VDC	0 VDC
White	NPN signal output	Redline sensor input	MASSO input with power/resistor jumper
Black	Unused in this application	Not connected	Not connected

The blue wire is the sensor’s DC common or 0 V reference. It should not be confused with protective earth or the machine’s chassis-ground connection.

The black conductor is present in the cable but is not used by the Redline wiring configuration we inspected. It should remain disconnected and individually insulated unless its purpose has been independently verified for your exact sensor revision.

Internal wiring of the FC-SPX306 sensor. Brown supplies positive DC power, blue is 0 V and white is the NPN signal output. The black conductor is unused in this application.

Redline and MASSO Voltage Difference

The original Redline controller provides approximately 5 VDC to the sensor through the brown and blue conductors:

Brown: +5 VDC
Blue: 0 VDC
White: NPN signal

PwnCNC conversion kits use a 24 VDC industrial sensor circuit:

Brown: +24 VDC
Blue: 0 VDC
White: NPN signal to MASSO
Black: Disconnected

The voltage difference does not require replacing this sensor because the FC-SPX306 is rated to operate from 5–24 VDC.

Understanding the NPN Output

The FC-SPX306 used on this machine has an NPN, sinking output.

An NPN sensor does not supply positive voltage through its signal wire when activated. Instead, it pulls the signal toward 0 V. In this installation, the white wire is the NPN signal conductor.

Because of this behavior, connecting the white wire directly to a MASSO input is not sufficient. The MASSO input also requires the PwnCNC power/resistor jumper used with NPN sensors.

The resistor jumper holds the MASSO input high while the sensor is inactive. When the optical sensor activates, its NPN output pulls the input toward 0 V, allowing MASSO to detect the change of state.

Connecting the Sensor to MASSO

When reusing this sensor with a PwnCNC MASSO conversion kit:

Connect the brown wire to the designated +24 VDC sensor supply.
Connect the blue wire to the designated 0 VDC sensor common.
Connect the white wire to the appropriate MASSO input.
Install the specified PwnCNC power/resistor jumper between +24 VDC and that same MASSO input.
Leave the black wire disconnected and individually insulated.

Follow the wiring diagram supplied with your conversion kit for the correct terminals and resistor-jumper placement.

Important: Do not substitute a plain wire jumper for the power/resistor jumper. Connecting +24 VDC directly to the NPN output without the required resistor could create a short circuit when the sensor activates.

Testing the Sensor in MASSO

Before attempting to home or move the machine, verify each sensor through the MASSO input-status screen.

For each sensor:

Confirm that the sensor receives approximately 24 VDC between the brown and blue wires.
Locate the assigned input on the MASSO input-status screen.
Trigger and release the optical sensor manually.
Confirm that the assigned input changes state each time.
Confirm that it returns to its normal state when the sensor is released.
Repeat the test several times before operating the axis.

If the input changes state but behaves opposite to the required homing logic, review the input configuration in MASSO. Do not reverse the sensor’s power polarity in an attempt to change its switching behavior.

Do not begin a homing cycle until every installed sensor has been tested individually.

Hardware Variations

This information applies to the F&C FC-SPX306 sensor and Onefinity Redline wiring inspected by PwnCNC.

Do not assume that all Onefinity machines or production revisions use identical sensors. Stop and verify the wiring if your machine has any of the following differences:

A different sensor model number
Different wire colors
A different number of conductors
A different connector
A different mounting bracket
A sensor labeled for a different voltage range
A sensor that does not respond correctly at 24 VDC

Wire colors are useful for identification, but they should not be the only evidence used when connecting unfamiliar hardware.

Help Us Expand This Research

PwnCNC is building a collection of brand- and machine-specific conversion information for the CNC community. Our goal is to document the details that are often difficult to find when installing a new controller or adapting existing machine hardware.

If your Onefinity uses a different sensor, connector, cable arrangement or controller revision, please send us:

Machine model and size
Original controller type
Sensor manufacturer and model number
Clear photographs of the sensor and connector
Photographs of any wire labels or pin markings
Measured sensor supply voltage
Confirmation of which conductor carries the signal
Whether the sensor is NPN or PNP
Your MASSO configuration backup, when available

Verified community contributions can help us identify production changes and improve future conversion-kit documentation.

Disclaimer

This information is provided for research and educational purposes. Disconnect power before opening connectors or modifying wiring. Confirm polarity and voltage before connecting the sensor to a controller.

Incorrect wiring can damage the sensor, controller input or power supply. PwnCNC cannot guarantee that every machine or production revision uses the same components or wiring documented here.