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Part of the Omron NX-Series Safety & I/O series — see the full model table, lifecycle status and replacement parts.

Omron NX-OD4121 8-point NPN output unit — front view showing the slim 12 mm wide body with 8 yellow output status LEDs across the front face and the screwless push-in 16-terminal connector on the bottom

Omron NX-OD4121 — NX Output Unit, 8 Point NPN, 24 VDC

SKU: NX-OD4121

USD 52.00

NX-series 8-point NPN transistor output unit, 24 VDC 0.5 A per point / 4 A per unit, screwless push-in connector, 12 mm wide

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Product Overview

The Omron NX-OD4121 is the 8-point NPN (sinking) transistor output unit for Omron's NX-series EtherCAT slice I/O system. manufactured by Omron Corporation. Hengyixin Automation stocks this I/O expansion unit in Xiamen and ships within 3-5 business days to most Asian, European, and North American ports. Specifications on this page were checked against Omron's NX-series I/O System brochure (R183).

The 8 outputs are arranged in one 8-bit I/O word with one shared common, each capable of switching up to 0.5 A at 24 VDC (4 A per unit total). The screwless push-in connector on the bottom accepts 0.2 to 1.5 mm² conductors with ferrules — fast wiring without screws, no re-torquing required after thermal cycling.

The NX-OD4121 ships from Xiamen with full datasheet documentation. The NPN output sinks current to 0 V when the output is ON — connect the load between +V (24 VDC supply) and the output terminal.

Key Features

  • 12 mm wide
  • 24 VDC rated output voltage
  • Standard speed: 0.1 ms ON / 0.8 ms OFF response time
  • 0.5 A per point / 4 A per unit maximum load current
  • SKU: NX-OD4121
  • Series: NX-series NX-OD4 Digital Output Units
  • Voltage: 12 TO 24 VDC
  • I/O: 8 points

Best-Fit Applications

  • LED indicator stack-light control on a machine operator console — 4 × NX-OD4121 outputs driving red / amber / green.
  • Relay-driver outputs on a control panel — 8 × NX-OD4121 outputs driving G2R-2-SND or G6B-4BND relays for higher-current AC switching
  • Stepper-motor pulse-direction control on a small pick-and-place — 4 × NX-OD4121 outputs providing PULSE/DIR/ENABLE for 2 stepper axes, 4 axes.

Buying Checklist

  • Pick NX-OD3257 for 4-point NPN high-speed pulse output — for stepper pulse control
  • Pick NX-OD6121-5 for 32-point NPN with MIL connector — pick for highest-density NPN applications
  • Pick NX-OD4256 for 8-point PNP sourcing — pick if your PLC's I/O is PNP sourcing

Technical Specifications

Model NX-OD4121
Series NX-series NX-OD4 Digital Output Units
Type 8-point NPN (sinking) transistor output, screwless push-in connector
Number of Output Points 8 points (1 byte, 1 common)
Internal I/O Common NPN (sinking)
Rated Output Voltage 12 to 24 VDC
Operating Load Voltage Range 10.2 to 28.8 VDC
Maximum Load Current 0.5 A per point / 4 A per unit
Leakage Current at OFF State 0.1 mA max
Residual Voltage at ON State 1.5 V max (at 0.5 A load)
Output Type Open collector transistor (NPN sinking)
Wire Range 0.2 to 1.5 mm² (AWG 24 to 16) with ferrule
5 VDC Backplane Current 80 mA max
24 VDC I/O Current 4 A max per unit (sum of all 8 outputs)
Operating Temperature 0 to +55 °C

Manufacturer documentation

Omron's own product page, where the manufacturer's current specification and lifecycle information are published. We are an independent distributor and cannot mirror those documents; the link goes to Omron's site.

FAQ for NX-OD4121

What's the difference between NX-OD4121 and NX-OD4256?
The NX-OD4121 (this SKU) is the 8-point NPN sinking version and the NX-OD4256 is the 8-point PNP sourcing version. Both are 12 mm wide, both have screwless push-in connectors, both are rated 0.5 A per point / 4 A per unit, both have 0.5 ms / 1.0 ms response.
What EtherCAT coupler does the NX-OD4121 require?
The NX-OD4121 requires an NX-ECC-series EtherCAT coupler on the left side of the NX slice. Three options are available: (1) NX-ECC201 (4 A I/O, 250 µs minimum cycle time) — standard pick for general-purpose applications where the slice total current is below 4 A.
Can the NX-OD4121 drive 24 VDC relay coils directly?
Yes — the NX-OD4121's 0.5 A per point output can drive any standard 24 VDC relay coil (G2R-2-SND at ~30 mA, G6B-4BND at ~25 mA per coil, LY2N-J at ~36 mA) with plenty of headroom. Wire the relay coil between the +V terminal and the output terminal (NPN sinking — output sources ground when ON).
What happens if an NX-OD4121 output shorts out?
The NX-OD4121 has per-channel overload protection with auto-recovery. When an output detects a short circuit (e.g. load shorted to ground, load current exceeds 0.5 A continuous, load wiring fault), the affected output shuts off within 100 µs, the output's yellow status LED turns OFF, and an error flag is set in the EtherCAT slave's diagnostic register (visible in Sysmac Studio's I/O map view and in the NJ/NX CPU's error log).

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