Omron NX-OD4256 — 8-Point PNP Output, 12 mm, 0.5 A
SKU: NX-OD4256USD 47.00
NX-series 8-point 24 VDC PNP transistor output unit, 0.5 A per point / 4 A per unit, screwless push-in connector, 12 mm wide. Standard-speed 0.5 ms ON / 1.0 ms OFF. EtherCAT slave, supports Sync I/O and Free-Run refresh modes.
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Product Overview
The NX-OD4256 is an 8-point standard-speed PNP (sourcing, +V output) transistor output unit for Omron's NX I/O family — the small 12-mm-wide slide-on module that adds 8 digital outputs to any NX-series EtherCAT slave slice built on a CJ1W-IC101 / NX-ECC201 / NX-ECC202 coupler or on a NX102-1000 / NX502-1300 NX machine controller. Each of the 8 outputs switches a 24 VDC load at 0.5 A per point (4 A total per unit), with overload and short-circuit protection that folds back current and signals an alarm to the controller.
Where the NX-OD4256 sits in the NX digital output family
The NX-OD4xxx and NX-OD5xxx families are split along four axes: output type (NPN sinking vs PNP sourcing), point count (4 / 8 / 16 / 32), current rating (0.5 A / 2 A per point), and speed (standard 0.5 ms vs high-speed 300 ns). The NX-OD4256 (this SKU) is the standard 8-point PNP 0.5 A variant with screwless push-in connector — the typical pick for machine-control outputs (24 VDC solenoid valves, indicator lamps, signal relays, contactors via interposing relays). The 16-point NPN sibling is NX-OD5121 (sinking, 16 points, 0.5 A per point); the 8-point NPN sinking is NX-OD4121.
Screwless push-in connector wiring (16 terminals)
The 16-terminal screwless push-in connector accepts solid wire 0.2 to 1.5 mm² (AWG 24 to 16) or stranded wire 0.2 to 1.5 mm² with ferrule. To insert a wire, push a 2.5 mm flat-blade screwdriver into the orange release slot directly above the wire entry, push the screwdriver in to open the spring clamp, insert the stripped 8 mm wire end into the round wire entry, then remove the screwdriver — the spring clamps the wire in place with a positive stop. To release, push the screwdriver back into the slot — the wire comes out.
EtherCAT synchronization, Free-Run, and Sysmac Studio config
The NX-OD4256 supports two I/O refreshing methods: Synchronous (DC / Distributed Clock synchronized) and Free-Run. In Synchronous mode, the output state is updated at each EtherCAT DC cycle (configurable from 250 µs minimum), with all 8 outputs changing simultaneously at the DC sync event — needed for closed-loop motion control, registration, and high-speed packaging lines. In Free-Run mode, the output refresh is asynchronous — the EtherCAT master writes to the NX-OD4256's PDO whenever convenient, and the module updates the outputs when the next scan completes (typically 500 µs later). Free-Run is the right mode for general-purpose digital outputs where cycle-to-cycle deterministic timing is not needed.
Key Features
- 8-point PNP sourcing transistor output for NX I/O bus
- 24 VDC load supply
- 0.5 A per point continuous output current, 4 A per unit maximum
- Standard-speed: 0.5 ms ON / 1.0 ms OFF response time
- Screwless push-in connector — solid and stranded wire 0.2 to 1.5 mm²
- Built-in overload and short-circuit protection with diagnostic flag
- Per-channel status feedback in EtherCAT PDO — alarm / overload
- Supports both Synchronous and Free-Run I/O refresh modes
- SKU: NX-OD4256
- Series: NX-Series Digital I/O Units — Transistor Output
- Voltage: 24 VDC
- I/O: 8 I/O
Best-Fit Applications
- Valve bank interface on a small pneumatic press — 8 × 24 VDC solenoid valves wired one each to NX-OD4256.
- Indicator lamp and HMI backlight driver on a machine console — 8 × NX-OD4256 outputs driving green/red/yellow stack lights, buzzer.
- Small motor contactor driver via interposing relays — 8 × NX-OD4256 outputs wired to 24 VDC relays, each relay switches.
- Conveyor VFD control on a packaging line — 8 × NX-OD4256 outputs wired to digital inputs on multiple 3G3MX2-A4110-V2 drives.
Buying Checklist
- Pick NX-OD4256 for 8 PNP outputs at 0.5 A per point with screwless push-in connector — the standard pick for 24 VDC valve / indicator / relay control
- Pick NX-OD5256 for 16 PNP outputs at 0.5 A per point — same 0.5 A rating but more dense on the NX-Bus
- Pick NX-OD4121 for 8 NPN sinking outputs — needed only for legacy Japanese-style NPN wiring
- Pick NX-OD3268 for 8 PNP outputs at 2 A per point — for high-current solenoid valves, heaters, and high-inrush loads
- Pick NX-OD3257 for 4 PNP high-speed outputs with 300 ns response — for step/direction pulse output to servos at up to 200 kHz
- Pick NX-OC2633 for 8 relay outputs — for AC switching or mixed-voltage loads that exceed the NX-OD4256's 30 VDC transistor limit
Technical Specifications
| Model | NX-OD4256 |
|---|---|
| Series | NX-Series Digital I/O Units — Transistor Output |
| Type | 8-point PNP transistor output, screwless push-in connector |
| Number of Outputs | 8 points (allocated as 1 word in EtherCAT PDO) |
| Output Type | PNP sourcing (sources +V to load) |
| Rated Output Voltage | 24 VDC (load supply, 15.0 to 28.8 VDC operating range) |
| Output Current per Point | 0.5 A max continuous (0.5 ms surge 1.0 A) |
| Output Current per Unit | 4 A max total (across all 8 points) |
| Output ON Response Time | 0.5 ms max |
| Output OFF Response Time | 1.0 ms max |
| Leakage Current (OFF) | 0.1 mA max |
| Residual Voltage (ON) | 1.0 V max at 0.5 A (Vce-sat of output transistor) |
| Overvoltage Protection | Output transient suppressors (TVS diodes) |
| Wire Range | 0.2 to 1.5 mm² (AWG 24 to 16), solid or ferrule stranded |
| Operating Temperature | 0 to +55 °C |
Resources & Downloads
FAQ for NX-OD4256
What's the difference between NX-OD4256 (PNP) and NX-OD4121 (NPN)?
Both are 8-point 24 VDC transistor outputs with 0.5 A per point and 4 A per unit, on the same 12 mm wide body. The difference is the output configuration: NX-OD4256 (this SKU) is PNP sourcing — each output sources +V to the load, with the load's other side returning to the 0 V terminal (European-style PNP wiring).
How fast can the NX-OD4256 switch compared to NX-OD3257?
The NX-OD4256 (this SKU) is the standard-speed output with 0.5 ms ON / 1.0 ms OFF response time — suitable for valve switching, indicator lamp driving, contactor driver, and general-purpose machine I/O at cycle times of 5-10 ms or slower. For high-speed pulse output (servo drive step/direction, VFD pulse command, indexing pulses, registration trigger), pick the NX-OD3257 instead — 300 ns ON / 300 ns OFF response, supporting pulse frequencies up to 200 kHz single-axis or 50 kHz two-axis.
How many NX-OD4256 can I mount on one NX-ECC201 coupler?
Physically and logically the NX-OD4256 mounts on the right-hand side of an NX-ECC201 / NX-ECC202 / NX-ECC203 EtherCAT coupler and daisy-chains with other NX I/O units. The hardware limit of the NX-Bus is 63 NX modules per slice (the NX-Bus protocol addressing is 6-bit, so 0-63). So in theory you could mount 63 × NX-OD4256 on one NX-ECC coupler for 504 outputs in one EtherCAT node.
Do I need NX-ECC201 or NX-ECC202 for NX-OD4256?
Both NX-ECC201 (the standard) and NX-ECC202 (the high-current variant) support the NX-OD4256 — the difference between the two is only the I/O current capacity on the I/O power supply side (4 A on NX-ECC201 vs 10 A on NX-ECC202). Pick the NX-ECC202 when you need more I/O current — large solenoid valve arrays, multi-motor contactor drivers, etc. Pick the NX-ECC201 when you have less I/O current demand and want a slightly lower-cost coupler.
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