The Allen-Bradley 1785-L20E is a PLC5 processor. This module is a major component of the legacy PLC5 product category. This controller is a single slot module that is compatible with 1771-A1B, -A2B, A3B, -A3B1, or the -A4B chassis. This controller is ideal for use medium range automation requirements as it supports a total of 512 I/O (mixed) and 512 input / output (complementary).

The 1785-L20E has a built-in volatile memory that amounts to 16KWords, which is maintained by a Lithium battery with catalog number 1785-XYC. This battery provides the necessary energy to maintain the contents of the controller’s SRAM to allow the controller to continuously function. For backup and increased system availability, non-volatile memory back up devices may be installed such as 1785-ME16 with 16Kwords, 1785-ME32 with 32Kwords, 1785-ME64 with 64 Kwords and 1785-ME100 with 100Kwords.

The 1785-L20E’s embedded communication interfaces include One (1) DH+ dedicated interface, One (1) DH+/Remote I/O (Adapter or Scanner) combination interface, One (1) serial port that supports RS-232, 423 and RS-422A standards and One (1) Ethernet channel that supports 10/100 Mbps transmission speed.

The 1785-L20E supports installation of Thirteen (13) chassis, overall. This includes the local rack where the controller is installed and additional Twelve (12) racks that me be used as distributed I/O racks.

The 1785-L20E supports a variety of data types such as Immediate or program constant, Integer, Float, Block, Message, PID, String and SFC status.

The 1785-L20E PLC -5/20E Ethernet/IP Programmable Controller by Allen-Bradley is a programmable controller with 16K word SRAM processor. This controller is installed in a 1771 I/O chassis’ controller slot. It is primarily used for processing user logic and for controlling the inputs and outputs of field devices connected to it. It has 512 maximum I/O link capacity with 512 mixed, or 512 in + 512 out complementary. The controller’s supported I/O Rack capacity is Four (4) and a Remote I/O chassis capacity of 12. The controller is installed on either the 1771-A1B, -A2B, A3B, -A3B1, or the -A4B I/O chassis, and draws a chassis backplane current of 3.6A.

The controller uses an Allen Bradley 1770-XYC Lithium battery module. The 1785-L20E has a maximum I/O scan time of 10 milliseconds between remote I/O adapter at 57.6 kbps scan speed, and 3 miliseconds between remote I/O adapter communication at 230.4 kbps scan speed, and it supports the half slot, the single slot, and the double slot addressing system.

The 1785-L20E controller also supports the Allen Bradley Bulletin 1771 I/O 8, 16, and the 32-point, and intelligent modules, and it comes with an internal Calendar/Clock with 1 program per scan accuracy and a maximum variation of plus or minus 5 minutes per month. The controller comes with 1 fixed Data Highway Plus (DH+) port with a 25-pin D-shell serial port, which supports standard EIA RS-232C and RS-423 for serial connection, and based 15-pin Ethernet/IP port with 10MB transmission speed, for connecting to devices on the Ethernet network.

The controller’s operating temperature is 32-140 degrees Fahrenheit at 5-95% non-condensing ambient relative humidity, and it will dissipate 65 BTU/hour of maximum heat when operational. The 1785-L20E controller can withstand a 30G shock, with 1G vibration at 10-500 Hertz when operational, and it is keyed in place via pins 40-42, and 54-56. The 1785-L20E weighs approximately 1.43 kilograms (3.2 pounds), and it is CSA, UL, and C-certified.