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1785-L20E

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Allen-Bradley 1785-L20E is the 16 K-word PLC-5/20E controller with a legacy 15-pin AUI Ethernet interface, fixed DH+, configurable DH+/Remote I/O, and serial communication.
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Technical specifications for 1785-L20E

  • Manufacturer:
    Allen-Bradley
  • Part Number:
    1785-L20E
  • Product Family:
    PLC-5
  • Product Type:
    PLC-5/20E Ethernet Processor
  • Stock:
    1
  • Processor Designation:
    PLC-5/20E
  • Maximum User Memory:
    16K words
  • Maximum I/O:
    512 any mix or 512 input plus 512 output in complementary mode
  • Ethernet Ports:
    1 channel
  • Ethernet Physical Interface:
    15-pin AUI transceiver port
  • Maximum Number of I/O Racks:
    4
  • Maximum I/O Chassis:
    13 total; 12 remote
  • Battery:
    1770-XYC
  • Chassis Location:
    Leftmost slot in a supported 1771 chassis
  • Keying Locations:
    Between 40 and 42; between 54 and 56
  • Operating Temperature:
    0 to 60°C
  • Storage Temperature:
    -40 to 85°C
  • Relative Humidity:
    5% to 95%, non-condensing
  • Dimensions:
    4.8 × 16.8 × 26.8 cm
  • Weight:
    1.43 kg
  • Tariff Code:
    8537101190
  • Country of origin:
    USA
  • Place of shipment:
    Xiamen,Fujian,China
By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

More Information

Overview Manuals Ethernet Setup I/O Capacity Project Recovery Application
  • Adds Ethernet communication to the PLC-5/20 controller while retaining serial and 1771 I/O operation
  • Confirm the processor memory and supported rack and chassis capacity before selecting a replacement
  • Preserve the Ethernet identity, communication routes, and ladder project before replacing the controller

1785-L20E adds an Ethernet path to the PLC-5/20 processor class while retaining the controller's serial and 1771 I/O responsibilities.

The official capacity table differentiates this model from larger L40E and L80E processors by memory, rack count, and total chassis allowance.

For maintenance, the network identity and communication routes are as important as the ladder application stored in the controller.

Availability, condition, price, and shipping time for 1785-L20E are confirmed during quotation.

Allen-Bradley 1785-L20E PLC-5/20E Ethernet Processor Manuals, Datasheets, Links

Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.

  • The Ethernet channel uses the documented 15-pin AUI transceiver interface.
  • TCP/IP communication supports controller access through the plant Ethernet network.
  • IP addressing and connected transceiver hardware must be recorded before replacement.
  • The official table lists 16K words of user memory for PLC-5/20E.
  • The processor supports up to four documented I/O racks.
  • Its chassis allocation is lower than the PLC-5/40E and PLC-5/80E families.
  • Back up the PLC-5 application and communication-channel configuration.
  • Preserve Ethernet addressing, message paths, and rack assignments.
  • Validate program execution and every required network consumer after restart.
  • PLC-5/20E control systems whose verified application fits the 16K-word memory and four-rack capacity
  • 1771 architectures requiring Ethernet TCP/IP through the controller's 15-pin AUI interface
  • Control applications combining Ethernet with serial, fixed DH+, and configurable DH+/Remote I/O communication
Description
Allen-Bradley 1785-L20E integrates PLC-5/20 control with an Ethernet TCP/IP channel for programming, messaging, and plant-network communication.

Its official processor table identifies 16K words of user memory, support for up to four I/O racks, and serial, Data Highway Plus, remote-I/O, and Ethernet connectivity.

Replacement work should preserve the controller project, Ethernet addressing, channel configuration, rack assignments, battery state, memory-module contents, and the complete hardware Series.
Revisions

Revision Part #

Also known as

1785-L20E Ser E
1785-L20E/E, Series E, Rev E
1785-L20E Ser F
1785-L20E/F, Series F, Rev F
Alternative Names
1785-L20E Allen-Bradley 1785-L20E Allen Bradley 1785-L20E PLC-5/20E 1785-L20E Bulletin 1785-L20E
Technical notes
1785-L20E commissioning requires the correct Series, supported 1771 chassis, saved PLC-5 project, IP configuration, AUI transceiver path, rack allocation, and channel settings; an Ethernet-port match alone is insufficient.
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FAQS

The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
How can a buyer distinguish Allen-Bradley 1785-L20E from other Ethernet PLC-5 processors?
Check the full L20E catalog, hardware Series, 16K memory class, Ethernet channel, chassis arrangement, and the port configuration shown on the installed processor.
What network information should be saved before changing Allen-Bradley 1785-L20E?
Record the IP configuration, BOOTP or assigned addressing method, subnet details, messaging paths, HMI connections, and any controller-to-controller communication used by the application.
Can Allen-Bradley 1785-L20E be selected only by matching its Ethernet port?
No. The processor Series, memory, rack capacity, 1771 chassis, application, communication-channel assignments, and network configuration must also match.
Why might a replacement Allen-Bradley 1785-L20E be unreachable on Ethernet?
Check the AUI transceiver path, IP settings, duplicate addresses, channel configuration, cabling, controller mode, and whether the saved project was restored correctly.
What should be inspected before inserting Allen-Bradley 1785-L20E into a chassis?
Verify the leftmost-slot position, chassis power, keying, connector condition, battery, memory module, and that field and network cables are clearly identified.
Does Allen-Bradley 1785-L20E require the original PLC-5 project for replacement?
A verified project is normally required to restore machine logic, data-table use, communication channels, rack assignments, and network behavior.
When should Allen-Bradley 1785-L20E not be substituted for Allen-Bradley 1785-L40E?
Do not substitute when the application exceeds L20E memory, I/O-rack, chassis, or communication requirements, or when the validated project and installation require the L40E catalog.

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