Allen-Bradley 1747-CP3 Safety-Enhanced Programming Cable: Reliable Control in Harsh Industrial Sites
The Allen-Bradley 1747-CP3 is a ruggedized RS-232 to DH-485 programming cable engineered for mission-critical communication between engineering workstations and Allen-Bradley SLC 500 series PLCs, including the SLC 5/01, 5/02, 5/03, 5/04, and 5/05 processors, as well as MicroLogix 1000 and MicroLogix 1100 controllers. In demanding industrial environments — petrochemical plants, power generation facilities, mining operations, water treatment stations, metallurgical processing lines, and continuous manufacturing cells — maintaining a stable, interference-free programming link is not a convenience; it is a safety imperative. The 1747-CP3 is built to meet that standard.
Signal integrity is the foundation of safe PLC programming. A degraded or intermittent RS-232 connection during an online program download or live monitoring session can cause unexpected processor faults, force the CPU into a faulted stop state, or — in worst-case scenarios — corrupt the ladder logic resident in the SLC 500 rack. The 1747-CP3 addresses this risk through a shielded, low-capacitance cable construction that suppresses common-mode noise from variable frequency drives (VFDs), motor starters, high-current bus bars, and adjacent relay coils. Its ferrite-core EMI suppression at both termination ends further reduces radiated interference pickup, ensuring that DH-485 protocol frames are transmitted without bit errors even in electrically noisy control cabinets.
Safety Reliability Table
| Parameter | Specification / Rating |
|---|---|
| Part Number | 1747-CP3 |
| Brand | Allen-Bradley (Rockwell Automation) |
| Series | SLC 500 / MicroLogix Accessories |
| Interface | RS-232 (DB-9 Male) to DH-485 (Mini-DIN 8-pin) |
| Compatible Processors | SLC 5/01, 5/02, 5/03, 5/04, 5/05; MicroLogix 1000, 1100 |
| Cable Length | Approx. 2 m (6.5 ft) — standard factory length |
| Shield Construction | Foil + braid shield, drain wire grounded at DB-9 shell |
| EMI Suppression | Ferrite cores at both ends |
| Operating Temperature | 0 °C to +60 °C (32 °F to 140 °F) |
| Storage Temperature | -20 °C to +85 °C |
| Surge / ESD Protection | Passive transient suppression via shielded construction |
| Protocol | DH-485 (Data Highway 485), RS-232 serial |
| Connector Retention | Thumbscrew locking on DB-9; keyed Mini-DIN on DH-485 port |
| Weight | 350 g |
| Country of Origin | United States |
| Warranty | 12 Months — covers manufacturing defects and signal integrity failure |
| Pre-shipment Testing | Full continuity, shield integrity, and loopback communication test |
Control Cabinet Protection Strategy
A safe and reliable SLC 500 control cabinet is never built around a single component. The 1747-CP3 programming cable operates as part of a broader protection architecture. Within the same cabinet, the Allen-Bradley 1746-P4 power supply provides regulated 24 VDC and 5 VDC rails to the SLC 500 chassis, and its built-in overcurrent protection prevents downstream module damage during load transients. The 1746-IB16 digital input module and 1746-OB16 digital output module handle field-level I/O, and their optically isolated input circuits ensure that high-voltage transients from solenoid valves or motor contactors do not propagate back into the backplane.
For analog process control loops — flow, pressure, temperature, and level — the 1746-NI4 analog input module provides 4–20 mA and 0–10 V signal conditioning with 12-bit resolution, while the 1746-NO4I analog output module drives control valves and variable speed drives with isolated current outputs. When the SLC 500 rack must communicate upstream to a supervisory SCADA system or a ControlLogix L7x gateway, the 1747-SDN DeviceNet Scanner module or a 1747-KE RS-232/DH-485 interface module extends the network reach without compromising the DH-485 segment integrity that the 1747-CP3 cable serves.
Surge protection at the cabinet entry point is equally critical. A Phoenix Contact TRABTECH surge protection device on the 24 VDC supply rail clamps lightning-induced transients before they reach the SLC 500 backplane. Similarly, a Weidmüller or DEHN signal line surge arrester on field instrument cables prevents induced surges from propagating into analog input modules. Together with the 1747-CP3’s shielded construction, these components form a layered defense against the electromagnetic and electrical threats common in heavy industrial environments.
For programming workstations that lack a native RS-232 COM port — increasingly common with modern laptops — a high-quality USB-to-RS-232 adapter with FTDI chipset (such as the Moxa UPort 1110 or Advantech USB-4604) is the recommended interface. Cheap adapters with Prolific PL2303 chipsets are known to cause intermittent communication faults with RSLinx Classic, which can interrupt online edits and trigger processor faults. The 1747-CP3 paired with a verified FTDI-based adapter ensures a stable, low-latency serial link for both program uploads and real-time monitoring.
Critical Industrial Safety Applications
Petrochemical and Refinery Plants: In continuous process environments where SLC 500 racks control pump stations, compressor interlocks, and emergency shutdown (ESD) sequences, the ability to perform safe online program modifications without interrupting the process is essential. The 1747-CP3 enables engineers to connect to the SLC processor’s DH-485 channel port for live monitoring of rung status, force bits, and data table values — all without requiring a processor mode change that would halt outputs. This capability is critical during hot-work permit procedures and process upset investigations.
Power Generation and Substation Control: Electrical substations and power plant auxiliary control systems frequently use SLC 500 PLCs for motor control center (MCC) sequencing, transformer protection interlocks, and generator synchronization logic. The 1747-CP3’s shielded construction is particularly valuable in these environments, where 50/60 Hz magnetic fields from large transformers and bus bars can induce noise on unshielded cables and corrupt serial communication frames.
Mining and Mineral Processing: Underground and surface mining operations subject control equipment to vibration, dust, and wide temperature swings. The 1747-CP3’s robust connector retention — thumbscrew locking on the DB-9 end and a keyed Mini-DIN on the DH-485 port — prevents accidental disconnection during maintenance activities in cramped, vibration-prone environments such as conveyor drive rooms and crusher control stations.
Water and Wastewater Treatment: Municipal water treatment facilities rely on SLC 500 systems for chlorination dosing, pump sequencing, and SCADA data acquisition. Maintenance technicians use the 1747-CP3 to perform periodic program audits, update setpoints, and troubleshoot I/O faults — tasks that must be completed safely and reliably to maintain continuous water supply and regulatory compliance.
Metallurgical and Steel Processing: Rolling mills, arc furnaces, and continuous casting lines generate extreme electromagnetic interference. The 1747-CP3’s ferrite-core EMI suppression and foil-braid shield construction make it one of the few programming cables capable of maintaining a stable DH-485 link in close proximity to high-current induction heating equipment and large DC drive systems.
Safety and Quality FAQ
Q1: What does the 12-month warranty cover for the 1747-CP3?
The 12-month warranty covers all manufacturing defects, connector failures, shield continuity faults, and signal integrity issues that arise under normal industrial use conditions. If the cable fails to establish or maintain a stable DH-485 communication link with a compatible SLC 500 or MicroLogix processor within the warranty period, we will provide a replacement unit at no charge. Warranty claims are processed within 3 business days of fault confirmation.
Q2: What pre-shipment testing is performed on each 1747-CP3 unit?
Every unit undergoes a full three-stage inspection before dispatch: (1) pin-to-pin continuity verification across all 8 DH-485 conductors and all active RS-232 lines; (2) shield integrity test confirming drain wire continuity and foil coverage; and (3) a live loopback communication test using RSLinx Classic to verify that the cable successfully establishes a DH-485 node connection. Units that fail any stage are quarantined and not shipped.
Q3: Is the 1747-CP3 compatible with all SLC 500 processor series and RSLinx Classic drivers?
Yes. The 1747-CP3 is compatible with all SLC 5/01 through 5/05 processors via the DH-485 channel port (Channel 0), and with MicroLogix 1000 and 1100 controllers. It is fully supported by the RSLinx Classic “SLC-CH0/DH485” driver on Windows 10 and Windows 11 (32-bit and 64-bit). For USB-to-RS-232 adapters, FTDI-chipset devices are strongly recommended for driver stability.
Q4: Can long-term supply and spare parts availability be guaranteed?
We maintain standing inventory of the 1747-CP3 to support ongoing maintenance programs, planned shutdowns, and emergency spare requirements. Orders are typically dispatched within 1–2 business days. For facilities managing large SLC 500 installed bases, we recommend holding at least one spare 1747-CP3 per maintenance kit, as programming cable failures during critical maintenance windows can extend unplanned downtime significantly. Contact our team to discuss volume pricing and consignment stock arrangements.
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