Programmable Controller | Allen-Bradley 1761-L20BWA-5A MicroLogix 1000

The Allen-Bradley 1761-L20BWA-5A is a compact fixed-configuration controller from the MicroLogix 1000 product line. Powered by a 120/240 VAC main power supply, it features a total of 20 digital I/O points alongside integrated analog input and output channels. The controller combines twelve 24 VDC sinking/sourcing discrete inputs, eight relay outputs, four differential analog inputs, and one analog output into a single base chassis for small-scale industrial automation.

Integrated Analog and Digital I/O Capability

The digital section consists of twelve 24 VDC inputs supporting both 24 VDC sink and source field wiring setups, paired with eight electromechanical relay outputs rated for 24 to 125 VDC or 0 to 240 VAC loads. Built-in analog channels are integrated directly on the base board rather than requiring add-on expansion modules, supporting voltage (-10.5 to +10.5 VDC) and current (-21 to +21 mA) signals for inputs, as well as 0 to 10 VDC or 4 to 20 mA for the single analog output channel.

Communication and Memory Architecture

The unit includes an integrated RS-232 communication port utilizing the DF1 protocol for programming, monitoring, and connecting to human-machine interfaces (HMIs) or network converters like the AIC+. Non-volatile memory is provided by an internal 1K EEPROM structured to hold up to 737 instruction words and 437 data table words, ensuring user logic and data remain stored during system power loss.

Technical Specifications

Installation Guidelines

Mount the controller horizontally inside an enclosure using standard 35 mm DIN rail or panel screws to ensure adequate convection airflow. Wire connections accept #14 to #22 AWG solid conductors or #16 to #22 AWG stranded conductors inserted into the removable pressure-plate terminal block. Ensure the chassis ground terminal is connected directly to a clean industrial ground point prior to connecting external power and signal wiring.

Frequently Asked Questions

Q: What is the key functional difference between the 1761-L20BWA-5A and the 1761-L20AWA-5A? A: The 1761-L20BWA-5A uses 24 VDC digital inputs, whereas the 1761-L20AWA-5A utilizes 120 VAC digital inputs. Both models feature a 120/240 VAC power supply and identical analog channel counts.

Q: Does the analog input capability require an additional module plugged into the chassis? A: No, the four analog inputs and one analog output are built directly onto the controller base circuit board without requiring external expansion racks.