Purchase now: Allen Bradley 1747-L30L Fixed Controller
Purchase now: Atlantechdrives provides you the 1747-L30L, a highly specialized, fast-acting «Fixed Hardware Style» programmable logic controller from the legendary Allen Bradley SLC 500 automation family. Built to integrate the processor, power supply, and I/O board into a single rugged «brick,» the 1747-L30L delivers 30 total I/O points. However, unlike standard models, the «L» configuration is engineered for a very specific electrical wiring standard: it features 18 Sourcing 24V DC inputs paired with 12 Sinking DC Transistor outputs. This unique polarity arrangement makes it the absolute perfect drop-in replacement for specific OEM manufacturing machines, rotary indexing tables, and high-speed packaging equipment that utilize sinking (NPN) field actuators and sourcing sensors.
Technical Specifications of the 1747-L30L
Powered by standard 120/240V AC line voltage, the 1747-L30L includes 1K of internal instruction memory. Its solid-state transistor outputs provide lightning-fast switching (under 1 millisecond), bypassing the mechanical latency of traditional relays.
- Part Number: 1747-L30L
- Controller Type: Fixed Hardware Style (Brick PLC)
- Total I/O Points: 30 Points
- Inputs: Eighteen (18) 24V DC Sourcing (Requires Sinking/NPN sensors)
- Outputs: Twelve (12) DC Transistor Sinking (Provides ground to load)
- Special Feature: Embedded High-Speed Counter (HSC)
- Line Power Requirement: 120 / 240V AC (50/60 Hz)
- Memory Capacity: 1K Instructions (Capacitor-backed RAM)
- Communication Port: DH-485 (RJ45 connector)
Expert Installation Advice: Sinking Transistor Logic
Understanding the «L» series output logic is where most technicians make costly errors. Expert Tip: The 12 outputs on the 1747-L30L are DC Sinking Transistors. When the PLC logic commands the output to turn ON, the module does not send out 24V DC; instead, it closes the circuit to ground (0V / DC Common). Therefore, you must wire your field devices (like solenoid valves or micro-relays) by connecting their positive terminal directly to a +24V DC power supply, and wiring their negative return line to the output terminal on the PLC. Additionally, because these are solid-state transistors, you must install a reverse-biased flyback diode across every inductive load to prevent the collapsing magnetic field from destroying the delicate sinking silicon inside the controller.
Maintenance and High-Speed Counting
The 1747-L30L features a built-in High-Speed Counter (HSC), making it ideal for tracking rapid pulses from rotary encoders. When maintaining the machine, ensure that the encoder wiring is shielded and routed completely separately from high-voltage AC cables. The high-speed inputs process pulses much faster than the standard PLC scan time, so any induced electrical noise will immediately cause false counts, resulting in incorrect cut lengths or material positioning errors.
Frequently Asked Questions (FAQs)
Q: Can I wire standard PNP (Sourcing) proximity sensors to the inputs?
A: No. The 1747-L30L features 24V DC Sourcing inputs, which means the controller supplies the positive voltage. You must use NPN (Sinking) sensors that complete the circuit to ground.
Q: Does this unit support expansion modules?
A: Yes. By removing the side port cover, you can attach an interconnect ribbon cable to connect a standard 2-slot 1746 expansion chassis to add analog or specialty communication modules.
Do you need more references from this brand? Explore our full catalog of Allen Bradley here.
The 30-point SLC fixed hardware provides high reliability for legacy systems often maintained with replacement relay sets.
