Purchase now: Allen Bradley 1747-L30D Fixed Controller
Purchase now: Atlantechdrives provides you the 1747-L30D, a highly specialized, heavy-duty «Fixed Hardware» programmable logic controller from the Allen Bradley SLC 500 lineup. While sharing the exact same 30 I/O footprint and 24V DC Sinking inputs as the L30C, the 1747-L30D differentiates itself entirely on the output side: it is equipped with 12 Solid-State AC Triac outputs. Mechanical relays eventually wear out and fail under high-frequency switching. Triacs, however, have zero moving parts. This makes the 1747-L30D the absolute ultimate hardware choice for high-speed indexing machinery, rapid packaging wrappers, and automated sorting conveyors where 120V AC actuators and solenoids must be cycled millions of times a year without mechanical failure.
Technical Specifications of the 1747-L30D
The 1747-L30D integrates the CPU, a 120/240V AC power supply, and the I/O board into one compact chassis. The solid-state Triacs provide incredibly fast AC switching, turning on exactly when the AC sine wave crosses zero volts, which drastically reduces electrical noise in the cabinet.
- Part Number: 1747-L30D
- Controller Type: Fixed Hardware Style
- Total I/O Points: 30 Points
- Inputs: Eighteen (18) 24V DC Sinking (NPN logic)
- Outputs: Twelve (12) AC Triac Solid-State
- Line Power Requirement: 120 / 240V AC
- Memory Capacity: 1K Instructions
- Communication Port: DH-485 via RJ45 jack
- Expansion Capability: Supports a 2-slot external chassis
Expert Tips: Mastering AC Triac Leakage Current
When transitioning from mechanical relays to solid-state Triacs, engineers frequently encounter the «Ghost Voltage» phenomenon. Expert Tip: Because of the physics of semiconductor silicon, Triacs are never 100% «off.» Even when the PLC logic commands the output to be false, a tiny amount of «leakage current» (around 2 mA) continues to bleed through the output terminal. If you wire a very modern, low-power device—such as a high-efficiency LED indicator lamp or a micro-relay—to the 1747-L30D, this 2 mA of leakage current might be enough to keep the LED dimly lit or prevent the micro-relay from dropping out. To solve this, you must install a «burden resistor» in parallel with the load to bleed off the leakage current and ensure the device turns completely off.
Maintenance and AC Load Limitations
Triacs are incredibly reliable, but they are strictly AC-only devices. Maintenance Warning: Never attempt to switch 24V DC power through the outputs of the 1747-L30D. Triacs require the alternating sine wave of an AC circuit crossing zero volts in order to turn off. If you pass DC voltage through a Triac, it will turn on successfully, but it will never turn off again until you physically pull the wire out of the terminal block. Furthermore, ensure you protect the module with external fast-blow fuses, as a dead short on the factory floor will instantly permanently destroy the solid-state Triac silicon.
Frequently Asked Questions (FAQs)
Q: What software do I use to program the 1747-L30D?
A: You must use Rockwell Automation’s RSLogix 500 software. You will connect your laptop to the RJ45 port using a 1747-UIC (USB to DH-485 converter) or a 1747-PIC adapter.
Q: Can I use the inputs for high-speed counting?
A: Yes, specific input channels on the 1747-L30D can be configured within the software to act as a High-Speed Counter (HSC), allowing you to accurately track rapid pulses from a rotary encoder.
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For universal fixed control, this 30-point unit integrates seamlessly with external combination I/O modules.
