Introduction
The Allen Bradley 1771-IR/D is a DC input module for the classic PLC-5 series. From a maintenance perspective, this module provides reliable sensing of DC field signals, converting them into logic-level inputs for PLC control. It is widely used in legacy automation systems where continuous monitoring, rapid response, and long-term reliability are critical. The 1771-IR/D’s robust construction minimizes downtime and simplifies field troubleshooting.
Technical Specifications
| Parameter |
Description |
| Model Number |
1771-IR/D |
| Module Type |
DC Input Module |
| Input Channels |
16 discrete DC inputs |
| Input Voltage Range |
24 VDC nominal (20–30 VDC operational) |
| Input Current per Channel |
7 mA typical |
| Isolation |
Channel-to-backplane isolation standard |
| Operating Temperature |
0°C to 60°C |
| Storage Temperature |
–40°C to +85°C |
| Dimensions (H × W × D) |
140 mm × 35 mm × 160 mm |
| Weight |
≈ 0.45 kg |
| Mounting |
1771 PLC-5 chassis slot |
Applications / Field Use
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Reading DC signals from sensors, switches, or contact closures in industrial processes
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Integration with motor control centers and discrete control panels
-
Legacy PLC-5 systems for water treatment, packaging, and material handling
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Systems where signal integrity and maintenance visibility are important
-
Retrofitting older installations while keeping original PLC architecture intact
Advantages / Engineering Benefits
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High reliability: Designed for continuous operation in industrial environments
-
Simplified maintenance: Easy diagnostics through LED status indicators
-
Channel isolation: Minimizes noise and interference affecting other modules
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Compact footprint: Fits standard 1771 racks without occupying excessive space
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Long service life: Reduced need for replacement or troubleshooting
Technical FAQs
-
How many input channels does the 1771-IR/D provide?
– 16 discrete DC inputs.
-
What is the nominal voltage for input signals?
– 24 VDC nominal, operational between 20–30 VDC.
-
Is channel-to-channel isolation provided?
– Yes, each input is electrically isolated from the backplane.
-
Can this module be hot-swapped?
– No, power must be removed before insertion or removal.
-
What indicators are present for diagnostics?
– LED status lights per input for quick field verification.
-
What is the typical input current per channel?
– Approximately 7 mA per active input.
-
Is it compatible with all PLC-5 chassis sizes?
– Yes, works with 4-slot to 13-slot 1771 chassis.
-
Can it handle inductive input devices?
– Yes, though external suppression may be recommended.
-
What is the weight of the module?
– Approximately 0.45 kg.
-
What is the typical operating environment?
– Industrial control cabinets at 0°C to 60°C, protected from direct moisture.
Recommended Related Models
| Model Number |
Description |
| 1771-IA |
AC input module, complementary to DC inputs |
| 1771-OBD |
DC output module for controlling field devices |
| 1771-NI16 |
16-channel analog input module for mixed signal applications |
| 1771-P4 |
Compatible PLC-5 power supply module |
Popular Allen Bradley Models
| Model Number |
Description |
| 1771-IR/D |
16-channel DC input module |
| 1771-OAN |
8-point AC output module |
| 1771-IA |
AC input module |
| 1771-OBD |
DC output module |
| 1771-NI8 |
8-channel analog input module |
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