Allen Bradley 1785-L30B PLC 5/30 Processor
The Allen‑Bradley 1785-L30B (also known as 1785L30) is a PLC‑5/30 series programmable logic controller processor. It occupies a single slot in a PLC‑5 chassis (e.g., 1771‑A4B) and provides 24K words of user program memory. The processor is designed for medium‑scale control systems and supports remote I/O, DH+ communication, and a built-in RS-232 port for programming.
Processor Specifications
User program memory: 24K words (battery backed).
Data memory: 8K words (bit, timer, counter, integer files).
Basic instruction speed: 0.44 µs (bit).
I/O capacity: up to 1024 digital points (with remote I/O).
Built-in power supply: 5V DC (5A) from chassis backplane.
Communication Ports
Channel 0: RS-232 (9-pin D-sub) for programming or ASCII.
Channel 1: DH+ (Data Highway Plus) via 3-pin terminal block for networking up to 64 PLCs.
Channel 2: RS-422/485 (for remote I/O scanner) – optional.
Memory and Battery
The 1785-L30B uses a lithium battery (1770-XYC) to retain program and data for 2 years. A removable memory cartridge (1785-M100) can store a backup program. The processor has a real-time clock (RTC) with date/time stamping for events.
Compatibility
The processor is compatible with 1771 I/O chassis and I/O modules (digital, analog, specialty). It supports remote I/O via 1771-ASB adapter modules. The DH+ port allows connection to PanelView HMIs and other PLC‑5 controllers. It can also be used with 1784-KTX card in an IBM PC for programming.
Programming Software
RSLogix 5 (version 4.0 or higher) is used for ladder logic programming. Languages: relay ladder diagram (LD). The processor supports 128 PID loops and up to 8 channel interrupts. Online editing is allowed (insert/delete rungs).
Status and Diagnostics
LEDs: POWER (green), RUN (green), FAULT (red), FORCE (yellow), BATT (yellow), COMM (green). A 3‑digit display shows processor mode and error codes. The processor includes a watchdog timer (WDT) with adjustable timeout (10–1000 ms).
Environmental and Physical
Dimensions: 184 mm height x 160 mm width x 210 mm depth. Weight: 1.2 kg. Operating temperature: 0 to 60°C; storage: -40 to 85°C. Humidity: 5% to 95% non-condensing. Vibration: 2 g (10–55 Hz). The processor meets UL 508 and CSA standards. It is not RoHS compliant (older unit).
Typical Applications
Used in legacy automotive assembly lines, material handling, and batch processing. The PLC-5/30 is widely found in retrofits and spare parts for existing installations.
Ordering and Documentation
Catalog number: 1785-L30B (1785L30). The processor is supplied without a battery (order separately). Manual: PLC-5 Programmable Controllers User Manual (1785-6.8.1).
