Purchase now: Allen Bradley 1747-SCNR ControlNet Scanner Module
Purchase now: Atlantechdrives provides you the 1747-SCNR, a high-performance ControlNet Scanner Module manufactured by Allen Bradley specifically for the SLC 500 programmable logic controller system. As factory automation complexity increases, routing individual sensor wires back to a centralized PLC becomes physically and economically unviable. The 1747-SCNR resolves this architectural challenge by acting as a distributed I/O network master. It allows the local SLC processor to communicate deterministically with remote I/O blocks, intelligent motor control centers, and variable frequency drives (VFDs) over a robust ControlNet coaxial network. Designed for critical applications where data delivery times must be mathematically guaranteed, the 1747-SCNR ensures that complex, high-speed machinery remains perfectly synchronized across sprawling manufacturing facilities.
Technical Specifications of the 1747-SCNR
The 1747-SCNR is engineered for maximum uptime and supports both non-redundant and fully redundant media configurations. It utilizes two separate BNC ports (Channel A and Channel B) to ensure continuous operation even if a primary network cable is severed on the factory floor.
- Part Number: 1747-SCNR
- Module Type: ControlNet Scanner Module (Master)
- Compatible Processors: SLC 5/02, 5/03, 5/04, 5/05
- Network Topology: ControlNet (Coaxial RG-6 media)
- Redundancy: Dual BNC ports (Channel A and B)
- Data Transfer Methods: Discrete I/O mapping and M0/M1 files
- Backplane Current Draw: 800 mA at 5V DC, 90 mA at 24V DC
- Network Access Port (NAP): Included for local programming access
Expert Tips: Mastering M0 and M1 Memory Files
Programming the SLC 500 to handle large amounts of network data requires specific techniques. Expert Tip: A fully loaded ControlNet network brings in vastly more data than the standard discrete I/O tables (I: and O: files) of the SLC processor can hold. To manage this, the 1747-SCNR places the network data into specialized memory buffers known as M0 (Output data) and M1 (Input data) files. Because the SLC processor takes a significant performance hit if it addresses M-files directly in every rung of ladder logic, you must write a specific subroutine using the COP (Copy File) instruction. This instruction should bulk-copy the data from the M1 file into standard N (Integer) files at the start of the logic scan, and copy N files out to the M0 file at the end of the scan. This technique drastically improves processor scan time and prevents ControlNet communication timeouts.
Installation Advice: Coaxial Taps and Terminators
ControlNet is a high-frequency RF network, making it highly sensitive to physical wiring errors. You cannot splice ControlNet cables using standard electrical connectors. You must use certified Allen Bradley ControlNet Taps (such as the 1786-TPR or 1786-TPS) to connect the 1747-SCNR to the main trunk line. Furthermore, to prevent RF signal reflection which will instantly crash the network, exactly two 75-ohm terminating resistors must be installed—one at the extreme physical beginning of the trunk line, and one at the extreme end. Never leave an open trunk port without a terminator.
Frequently Asked Questions (FAQs)
Q: Can I install the 1747-SCNR in slot 0 of the chassis?
A: No. Slot 0 is strictly reserved for the SLC processor. The 1747-SCNR can be placed in any other available slot in the local chassis or an expansion chassis.
Q: What software is required to configure the ControlNet network?
A: In addition to RSLogix 500 for the PLC ladder logic, you must use RSNetWorx for ControlNet. This software allows you to «schedule» the network, defining the exact macrocycle and data update rates for all connected nodes.
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This ControlNet scanner provides deterministic communication and integrates seamlessly with larger architectures via the 1756-CN2 ControlLogix bridge.
