Allen-Bradley 1771-OFC PLC 12-Bit Analog Output Module
The 1771-OFC is a two-slot 12-bit analog output module engineered for legacy Allen-Bradley PLC systems, including PLC-2, PLC-3, and PLC-5 platforms. Featuring four single-ended output channels, an onboard processor, and dedicated memory, the module continuously scans memory registers to perform Digital-to-Analog (D/A) conversions independently. It delivers flexible current and voltage outputs to drive actuators, valves, and speed drives across complex industrial process loops.
Channel Signal Ranges and Conversion Processing
The 1771-OFC converts 12-bit digital words into analog voltage or current signals across all four channels. Supported output ranges include 0 to +5 VDC, +1 to +5 VDC, 0 to +10 VDC, -10 to +10 VDC, 0 to +20 mA, +4 to +20 mA, and -20 to +20 mA. Data words can be processed in either 12-digit natural binary or 3-digit BCD format to match controller programming structures.
System Integration and Chassis Installation
Occupying two adjacent slots within a standard 1771 I/O chassis, the module connects to field equipment via a 12-terminal 1771-WH field wiring arm, allowing module removal and replacement without disturbing field wiring. Physical chassis keying utilizes plastic bands placed between pins 2–4 and 6–8 on the left slot connector, and pins 4–6 and 32–34 on the right slot connector.
Power Requirements and Isolation Diagnostics
The 1771-OFC draws 1.4 A at 5 VDC from the backplane supply and requires a separate external DC power supply for output loop excitation. Optoelectrical isolation rated at 1,500 V protects backplane logic from field voltage surges and ground loops. Front-panel status indication includes a red Fault LED that flashes during active faults and remains illuminated continuously when operating in run mode.
| Parameter | Specification |
|---|---|
| Model | 1771-OFC |
| Brand | Allen-Bradley |
| Product Type | Analog Output Module |
| System Compatibility | PLC-2, PLC-3, and PLC-5 Systems (1771 I/O Chassis) |
| Number of Outputs | 4 single-ended channels |
| Module Width | 2 slots |
| Resolution | 12-Bit |
| Data Formats | Natural Binary, 3-digit BCD |
| Voltage Output Ranges | 0–5 VDC, 1–5 VDC, 0–10 VDC, -10 to +10 VDC |
| Current Output Ranges | 0–20 mA, 4–20 mA, -20 to +20 mA |
| Backplane Current Requirement | 1.4 A @ 5 VDC |
| Electrical Isolation | 1,500 V optoelectrical |
| Field Wiring Arm | 1771-WH (12 terminals) |
| Left Connector Keying Position | Between pins 2–4 and 6–8 |
| Right Connector Keying Position | Between pins 4–6 and 32–34 |
| Weight | 1.94 lbs (0.88 kg) |
Frequently Asked Questions
Q: How many chassis slots does the 1771-OFC module occupy? A: The 1771-OFC is a double-wide module that requires two adjacent slots in a standard Allen-Bradley 1771 I/O chassis.
Q: What analog signal types can the 1771-OFC output? A: It supports user-selectable voltage ranges (0–5 V, 1–5 V, 0–10 V, ±10 V) and current ranges (0–20 mA, 4–20 mA, ±20 mA) across all four channels.
Q: Which field wiring arm is required for external wiring connections? A: The module connects to field wiring using a 12-terminal 1771-WH field wiring arm, allowing quick-disconnect module swapping without unwiring.
Allen-Bradley 1771-OFC PLC 12-Bit Analog Output Module
Allen-Bradley 1771-OFC PLC 12-Bit Analog Output Module
The 1771-OFC is a two-slot 12-bit analog output module engineered for legacy Allen-Bradley PLC systems, including PLC-2, PLC-3, and PLC-5 platforms. Featuring four single-ended output channels, an onboard processor, and dedicated memory, the module continuously scans memory registers to perform Digital-to-Analog (D/A) conversions independently. It delivers flexible current and voltage outputs to drive actuators, valves, and speed drives across complex industrial process loops.
Channel Signal Ranges and Conversion Processing
The 1771-OFC converts 12-bit digital words into analog voltage or current signals across all four channels. Supported output ranges include 0 to +5 VDC, +1 to +5 VDC, 0 to +10 VDC, -10 to +10 VDC, 0 to +20 mA, +4 to +20 mA, and -20 to +20 mA. Data words can be processed in either 12-digit natural binary or 3-digit BCD format to match controller programming structures.
System Integration and Chassis Installation
Occupying two adjacent slots within a standard 1771 I/O chassis, the module connects to field equipment via a 12-terminal 1771-WH field wiring arm, allowing module removal and replacement without disturbing field wiring. Physical chassis keying utilizes plastic bands placed between pins 2–4 and 6–8 on the left slot connector, and pins 4–6 and 32–34 on the right slot connector.
Power Requirements and Isolation Diagnostics
The 1771-OFC draws 1.4 A at 5 VDC from the backplane supply and requires a separate external DC power supply for output loop excitation. Optoelectrical isolation rated at 1,500 V protects backplane logic from field voltage surges and ground loops. Front-panel status indication includes a red Fault LED that flashes during active faults and remains illuminated continuously when operating in run mode.
| Parameter | Specification |
|---|---|
| Model | 1771-OFC |
| Brand | Allen-Bradley |
| Product Type | Analog Output Module |
| System Compatibility | PLC-2, PLC-3, and PLC-5 Systems (1771 I/O Chassis) |
| Number of Outputs | 4 single-ended channels |
| Module Width | 2 slots |
| Resolution | 12-Bit |
| Data Formats | Natural Binary, 3-digit BCD |
| Voltage Output Ranges | 0–5 VDC, 1–5 VDC, 0–10 VDC, -10 to +10 VDC |
| Current Output Ranges | 0–20 mA, 4–20 mA, -20 to +20 mA |
| Backplane Current Requirement | 1.4 A @ 5 VDC |
| Electrical Isolation | 1,500 V optoelectrical |
| Field Wiring Arm | 1771-WH (12 terminals) |
| Left Connector Keying Position | Between pins 2–4 and 6–8 |
| Right Connector Keying Position | Between pins 4–6 and 32–34 |
| Weight | 1.94 lbs (0.88 kg) |
Frequently Asked Questions
Q: How many chassis slots does the 1771-OFC module occupy? A: The 1771-OFC is a double-wide module that requires two adjacent slots in a standard Allen-Bradley 1771 I/O chassis.
Q: What analog signal types can the 1771-OFC output? A: It supports user-selectable voltage ranges (0–5 V, 1–5 V, 0–10 V, ±10 V) and current ranges (0–20 mA, 4–20 mA, ±20 mA) across all four channels.
Q: Which field wiring arm is required for external wiring connections? A: The module connects to field wiring using a 12-terminal 1771-WH field wiring arm, allowing quick-disconnect module swapping without unwiring.
