Description
The 1756-HSC is a high-speed counter module manufactured by Allen-Bradley (Rockwell Automation), belonging to the ControlLogix 1756 I/O platform. It provides two independent counter channels, each with A, B, and Z inputs, and four current-sourcing outputs that can be configured to activate based on counter values independently of the controller’s scan cycle. The 1756-HSC is designed for applications requiring precise pulse counting, position measurement, or rate detection from encoders, flowmeters, and proximity sensors.
Application Scenarios
A cut-to-length line in a paper converting facility uses a rotary encoder to track material feed and trigger a flying shear at precise intervals. The existing control strategy relies on the controller’s periodic task to compare the encoder count against a target and command the shear—a method that introduces jitter of several milliseconds depending on communication load and task scheduling. At line speeds above 200 meters per minute, this jitter translates to cut-length variation that exceeds the customer’s ±2mm tolerance. The 1756-HSC addresses this by performing the comparison internally: the module’s on-board outputs can be configured with turn-on and turn-off count values, and the output asserts in hardware when the counter reaches those presets, independent of the controller’s scan or the EtherNet/IP connection’s RPI . The shear trigger fires within microseconds of the encoder reaching the target position, eliminating the scan-dependent variability that the software comparison approach could not overcome. The 1756-HSC also accepts the encoder’s Z-channel as a reset input, allowing the counter to re-synchronize to a physical reference mark once per revolution and prevent cumulative position drift.
Parameter
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1756-HSC |
| Manufacturer | Allen-Bradley / Rockwell Automation |
| Product Category | High-Speed Counter Module |
| Counters | 2 independent channels |
| Inputs per Counter | 3 (A, B, Z for gate/reset) |
| Outputs | 4 (2 per group), current sourcing |
| Max Input Frequency | 1 MHz (counter mode, A input); 250 kHz (encoder mode, A/B) |
| Count Range | 0 to 16,777,214 |
| Backplane Current | 300 mA @ 5.1 VDC; 3 mA @ 24 VDC |
| Power Dissipation | 5.6 W @ 60°C (19.1 BTU/hr) |
| Isolation Voltage | 125V continuous, input group-to-backplane |
| Operating Modes | Counter, Encoder x1, Encoder x4 |
| Output Delay | OFF to ON: 20 µs nominal; ON to OFF: 60 µs nominal |
| Operating Temperature | 0°C to 60°C |
| Slot Width | 1 slot, any chassis slot |
| Terminal Block | 1756-TBCH or 1756-TBS6H (ordered separately) |
