{"product_id":"allen-bradley-1785-lt-b-plc-5-classic-programmable-controller-module","title":"Allen-Bradley 1785-LT\/B PLC-5 Classic Programmable Controller Module","description":"\u003ch2\u003eAllen-Bradley 1785-LT\/B PLC-5 Classic Programmable Controller Module\u003c\/h2\u003e\n\u003cp\u003eThe \u003cstrong\u003eAllen-Bradley 1785-LT\/B\u003c\/strong\u003e, also cataloged as the \u003cstrong\u003e1785-LT\u003c\/strong\u003e programmable controller module, operates as a dedicated hardware component for centralized logic processing and network orchestration within 1771 I\/O chassis architecture. Designed for insertion into the left-most slot of a 1771 chassis, this controller executes digital discrete instructions, analog data processing, and industrial communications via Data Highway Plus (DH+) and RS-232-C\/422-A\/423-A serial links without relying on external coprocessing hardware.\u003c\/p\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003cfigure class=\"table\"\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003cstrong\u003eParameter\u003c\/strong\u003e\u003c\/th\u003e\n\u003cth\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003e1785-LT\/B\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eAllen-Bradley\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eUSA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e1.4 kg\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDimensions\u003c\/td\u003e\n\u003ctd\u003e5.1 cm x 27.9 cm x 15.2 cm\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Temp\u003c\/td\u003e\n\u003ctd\u003e0 to 60 deg C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Consumption\u003c\/td\u003e\n\u003ctd\u003eBackplane load current dependent on 1771 chassis supply\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eEmbedded Memory\u003c\/td\u003e\n\u003ctd\u003e6K words SRAM\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMemory Expansion\u003c\/td\u003e\n\u003ctd\u003eUp to 14K words (1785-MR 4K RAM, 1785-MS 8K RAM, 1785-MJ 8K EEPROM)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eProgram Scan Time\u003c\/td\u003e\n\u003ctd\u003e2 ms per K words (bit logic), 8 ms per K words (typical application)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eI\/O Capacity\u003c\/td\u003e\n\u003ctd\u003e512 inputs + 512 outputs (max 3072 points any mix, 512 analog channels)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChassis Rack Support\u003c\/td\u003e\n\u003ctd\u003eLocal: Up to 4 racks (1 resident); Remote: Up to 3 racks\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCommunication Ports\u003c\/td\u003e\n\u003ctd\u003e1x DH+ channel, RS-232-C \/ RS-422-A \/ RS-423-A serial, Control Coprocessor port\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDH+ Scan Time per Rack\u003c\/td\u003e\n\u003ctd\u003e10 ms at 57.6 kbit\/s, 7 ms at 115.2 kbit\/s, 3 ms at 230.4 kbit\/s\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRelative Humidity\u003c\/td\u003e\n\u003ctd\u003e5 to 95% non-condensing\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eShock Resistance\u003c\/td\u003e\n\u003ctd\u003e30G\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003ch3\u003eBackplane Bus Dynamics \u0026amp; Firmware Synchronization\u003c\/h3\u003e\n\u003cp\u003eThe 1785-LT\/B interfaces directly with the 1771 backplane bus to maintain high-velocity execution of local I\/O cycles and control coprocessor transactions. Firmware flash compatibility ensures synchronized deterministic instruction timing across legacy 1771 I\/O modules, preventing backplane bus contention during high-density I\/O scan sequences. Network throughput scales dynamically across the DH+ medium based on configured baud rates, isolating serial handshake latencies from real-time ladder execution cycles.\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003eQ: What is the backplane slot requirement for installing the 1785-LT\/B module?\u003c\/p\u003e\n\u003cp\u003eA: The 1785-LT\/B controller must be installed exclusively in the left-most slot (Slot 0) of a compatible 1771 I\/O chassis to properly interface with backplane power lines and local I\/O bus lines.\u003c\/p\u003e\n\u003cp\u003eQ: Can memory be upgraded beyond the 6K words embedded SRAM onboard?\u003c\/p\u003e\n\u003cp\u003eA: Yes, total memory capacity can be expanded up to 14K words by installing optional memory modules, including the 1785-MR (4K RAM), 1785-MS (8K RAM), or 1785-MJ (8K EEPROM).\u003c\/p\u003e\n\u003cp\u003eQ: What are the communication scan rates for remote I\/O racks connected via DH+?\u003c\/p\u003e\n\u003cp\u003eA: The scan time per remote rack varies with the selected transmission rate: 10 ms at 57.6 kbit\/s, 7 ms at 115.2 kbit\/s, and 3 ms at 230.4 kbit\/s.\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003cp\u003eEnsure the 1771 chassis power supply is completely de-energized prior to inserting or removing the 1785-LT\/B controller module to prevent backplane edge connector damage. Seat the module firmly into the left-most slot of the chassis until the top and bottom card guides lock securely into position. Maintain proper grounding by connecting the chassis grounding stud directly to the central enclosure earth ground bus using low-impedance copper conductor. Maintain physical isolation between communication cables (DH+ trunk, RS-232\/422 serial lines) and high-voltage AC power wiring to prevent inductive noise coupling.\u003c\/p\u003e","brand":"Allen-Bradley","offers":[{"title":"Default Title","offer_id":43748494082138,"sku":"1785-LT\/B","price":123.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0612\/4601\/3530\/files\/1785-LTB2.jpg?v=1785232664","url":"https:\/\/www.plcmasters.com\/products\/allen-bradley-1785-lt-b-plc-5-classic-programmable-controller-module","provider":"PLC Masters Ltd.","version":"1.0","type":"link"}