Application Scenarios
Consider a packaging machinery OEM operating a legacy high‑speed carton forming line controlled by a PLC‑5 system. The machine requires precise electronic cam profiling for its cut‑to‑length positioning system, but the PLC’s standard output cannot generate the high‑frequency pulse trains needed for accurate servo following. The 1771‑HS1 solves this by taking over the motion execution, communicating directly with the 1394‑series servo drive via its SERCOS fiber‑optic link. The PLC retains supervisory control while the 1771‑HS1 handles the real‑time position loop, eliminating missed cuts and reducing product waste by over 15% .
Parameters
| Main Parameters | Value/Description |
|---|---|
| Product Model | 1771‑HS1 |
| Manufacturer | Allen‑Bradley (Rockwell Automation) |
| Product Category | Servo Controller Module / Motion Control Interface |
| Controlled Axes | 1 axis (single‑axis servo or stepper motor) |
| Communication Protocol | SERCOS‑I (2 Mbps or 4 Mbps optical link) |
| Memory | 32 KB CMOS RAM on 1771‑HM cartridge with lithium battery backup |
| Pulse Output Frequency | Up to 2 MHz for step/direction control |
| Speed Resolution | 0.01 RPM |
| Acceleration Resolution | 0.01 RPM/s |
| Compatible Processors | PLC‑5/10, /20, /40, /60, /80 series |
| Compatible Drives | Allen‑Bradley 1394 series SERCOS‑I drives |
| Installation | 1771 Universal I/O chassis (e.g., 1771‑A1B, A2B, A3B) |
| Operating Temperature | 0°C to 60°C (32°F to 140°F) |
| Storage Temperature | -40°C to 85°C (-40°F to 185°F) |
| Vibration Rating | 5 g peak, 10–500 Hz |
| Weight | Approx. 1.3 kg |
Technical Principles and Innovative Values
Innovation Point 1: Off‑load Motion Processing from the PLC Scan Cycle
Unlike PLC‑based pulse outputs that suffer from scan‑induced timing jitter, the 1771‑HS1 operates as an independent motion engine with its own 32 KB memory . It executes positioning profiles, acceleration ramps, and electronic gearing entirely in hardware, freeing the PLC‑5 processor for logic and process control tasks.
Innovation Point 2: SERCOS Fiber‑Optic Communication for Noise Immunity
The 1771‑HS1 communicates with servo drives via the SERCOS‑I protocol over fiber‑optic cabling, offering immunity to electrical noise that plagues analog command signals in heavy industrial environments . This digital link enables real‑time position feedback at rates up to 4 Mbps, significantly improving system responsiveness compared to analog torque or velocity command methods.
Innovation Point 3: Removable Memory Cartridge with Battery Backup
The module’s 32 KB memory resides on a removable 1771‑HM cartridge, allowing rapid re‑configuration or replacement of motion programs without reprogramming from scratch . The integrated 3.6V lithium battery preserves program and motion profile data during power‑down, ensuring seamless restart after outages .
Innovation Point 4: Multifunction I/O and Diagnostic Integration
The 1771‑HS1 features a front panel with four red and green LEDs providing immediate visual status of drive communications, fault conditions, and axis activity . An integrated RS‑232 port supports serial communication with configuration terminals or external devices, while the dual differential inputs accept high‑speed encoder feedback for closed‑loop positioning .
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