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Omron CS1W-CT021 high-speed counter unit in the shipping carton with the type label visible

Omron CS1W-CT021 — 2-Axis High-Speed Counter, 500 kHz

SKU: CS1W-CT021

USD 466.00

2-axis CS-series high-speed counter unit, 500 kHz per channel, 32-bit range, 5/12 V line-driver inputs, CX-Programmer setup.

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Product Overview

The Omron CS1W-CT021 is a Special I/O unit for CS1-series PLCs that adds two high-speed counter channels. Each counter takes pulse inputs up to 500 kHz from a 5 V or 12 V line-driver encoder, or up to 50 kHz from an NPN open-collector output, and keeps a 32-bit total (-2,147,483,648 to +2,147,483,647). Standard ladder scans of a CS1H are too slow for encoder feedback — the CS1W-CT021 handles the counting in hardware and the CPU only reads the result.

What it does in a machine

Wire encoder A / B (or pulse + direction, or up/down pulse) into the CT021 terminals, and the unit captures every edge in hardware. With phase-differential A / B inputs, the CT021 multiplies by ×1, ×2, or ×4 in the firmware — set the mode in CX-Programmer to match the encoder resolution. Up to four external control inputs cover gate, preset, reset, capture, stop/capture/reset, and reset-enable functions. Counter matches (range compare, target compare, latch, programmable output with hysteresis) drive four external outputs plus 28 internal flags per counter — the internal flags let the CPU react to a setpoint before the next scan completes.

CT021 vs the other Omron counter options

The CT021 is the 2-axis model. If you need four counter channels in one unit, step up to the CS1W-CT041 (4-axis) — only the CT041 accepts 24 V line-driver inputs; the CT021 is limited to 5 V and 12 V. If the system is on a CJ-series CPU rack, the matching unit is the CJ1W-CT021, which uses the same chip and the same CX-Programmer settings in the smaller CJ form factor. For very simple counting where 500 kHz is overkill and one channel is enough, the high-speed inputs on a CP1H CPU (X / Y axis) can save the cost of a specialty unit.

Before ordering

Confirm the encoder line-driver voltage is 5 V or 12 V — for 24 V line-driver encoders you need the CS1W-CT041 or an external level converter. Set the rotary machine number on the front of the unit to a free slot (0-95) before mounting it. The CT021 draws 5 VDC 0.45 A from the CS1 backplane, so reserve the slot in CX-Programmer's I/O table ahead of the physical build.

Key Features

  • CS-series Special I/O high-speed counter unit
  • 2 counter channels per unit (CT021); 4 with CS1W-CT041
  • 500 kHz per channel with 5 V or 12 V line-driver input
  • 50 kHz per channel with NPN open-collector input
  • 32-bit count range per channel
  • Phase-differential (×1/×2/×4), up/down pulse, pulse + direction
  • Linear, ring, and preset counting modes
  • 4 external inputs + 4 external outputs per unit; 28 internal flags per counter
  • Counter match / target match can trigger a CPU interrupt task
  • Settings can be changed during operation via CX-Programmer
  • SKU: CS1W-CT021
  • Series: CS1W-CT021
  • I/O: 500 I/O

Best-Fit Applications

  • Encoder feedback on a cut-to-length or coil-winding machine where ladder scan is too slow
  • Speed / position verification on a CS1 retrofit that needs to read a 24V line-driver encoder
  • Pulse counting from a flow meter or batching system with 32-bit accumulation
  • Parts counter on a high-speed filling line that needs sub-scan reaction to a counter match
  • Triggering a CS1H interrupt task from a cam or registration mark without polling

Buying Checklist

  • Pick CS1W-CT021 for 2 counter channels — pick CS1W-CT041 if you need 4 channels or a 24 V line-driver encoder.
  • Pick CJ1W-CT021 instead when the CPU is a CJ1 / CJ2 — same chip in the smaller CJ form factor.
  • Confirm the encoder output is 5 V or 12 V line driver; CT021 does not accept 24 V line-driver signals.
  • Set the unit's machine number (0-95) on the front rotary switch before wiring — CT021 and CT041 cannot share a number.
  • Reserve the slot in CX-Programmer's I/O table ahead of mounting so the rest of the rack knows the unit is there.

Technical Specifications

Model CS1W-CT021
Type CS-series Special I/O high-speed counter (CPU bus unit)
Counter Channels 2 (use CS1W-CT041 for 4 channels)
Count Range 32-bit signed (-2,147,483,648 to +2,147,483,647)
Max Input Frequency 500 kHz / channel (line driver); 50 kHz / channel (open-collector)
Input Types RS-422 line driver (5 V or 12 V on CT021); NPN open-collector
Pulse Input Modes Phase differential (×1 / ×2 / ×4), up / down pulse, pulse + direction
Counting Modes Linear, ring, preset
External I/O 4 inputs + 4 outputs per unit; up to 28 internal flags per counter
Configuration CX-Programmer; settings editable during operation
Power 5 VDC 0.45 A from CS1 backplane
Compatible CPUs CS1G, CS1H, CS1D; CS1W-CT041 required for 24 V line driver

FAQ for CS1W-CT021

What is the difference between CS1W-CT021 and CS1W-CT041?
The CS1W-CT021 has 2 counter channels; the CS1W-CT041 has 4. The CT041 is also the only one of the two that accepts 24 V line-driver inputs — the CT021 is limited to 5 V and 12 V. Both use the same RS-422 line-driver or NPN open-collector signals, the same 500 kHz maximum, and the same CX-Programmer setup. Pick CT041 when you have more than two encoders or any 24 V line-driver signal.
Can CS1W-CT021 work on a CJ-series rack?
No — the CS1W-CT021 is a CS-series CPU-bus unit and physically only fits a CS1 rack. For CJ1 / CJ2 systems, use the CJ1W-CT021, which uses the same chip and the same CX-Programmer settings. For NJ-series controllers, the same chip is built into the NJ CPU as the encoder counter inputs — no specialty unit is needed for a few channels of counting.
How is the CS1W-CT021 configured?
Through CX-Programmer on a PC connected to the CS1 CPU. You set the pulse mode (phase differential, up / down pulse, or pulse + direction), the counting mode (linear, ring, or preset), the count value, and the match values for the internal flags. The settings are saved in the unit itself, not in the CPU project, so a CPU program download does not change them — they have to be re-loaded with the IOWR instruction or the CX-Programmer CT021 editor.
Does CS1W-CT021 need external 24 V power?
No. The unit draws 5 VDC 0.45 A from the CS1 backplane. It does not need an external 24 VDC supply for the encoder excitation; you power the encoder separately and route only the A / B / Z signals back to the unit. The external control inputs and outputs on the CT021 use the same backplane 5 V referenced logic.

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