Product Overview
The Allen-Bradley 1771-IH is a digital DC input module designed for the PLC 5 family and Bulletin 1771 I/O system. This rack-mountable module provides eight input channels and uses a wiring arm for straightforward installation. It operates on a DC supply with a voltage range of 24 to 48 Volts DC, making it suitable for a variety of industrial control applications.
With its robust design and reliable performance, the 1771-IH is a trusted choice for monitoring discrete DC signals in manufacturing and process environments. Its status indicators provide immediate visual feedback on input states, simplifying diagnostics and maintenance.
Technical Specifications
Below are the key specifications for the Allen-Bradley 1771-IH module:
| Specification |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1771-IH |
| Module Type |
Digital DC Input Module |
| Number of Inputs |
8 Inputs |
| Voltage Category |
10-60 Volts DC, Sink (Source Load) |
| DC Operating Voltage |
24-50 Volts |
| Backplane Current |
74 Milliamperes |
| Max DC Off-State Current |
0.7 Milliamperes |
| Typical DC Signal Delay (On) |
15 (±7) ms |
| Typical DC Signal Delay (Off) |
20 (±9) ms |
| Wiring Arm |
1771-WA |
| Model Status |
Earlier Model |
| Typical AC Signal Delay (Off) |
24 (±10) ms |
| Mounting |
Rack Mountable |
Additionally, the module has a maximum on-state voltage of 10V DC, a maximum off-state voltage of 4.5V DC, and a maximum off-state current of 1 mA. The input impedance ranges from 2.5–3K Ω in the on-state and 5–6K Ω in the off-state. Eight red status indicators are provided for each channel.
Signal propagation delays are specified at 15 ms (±7 ms) for both low-to-high and high-to-low transitions. The backplane current is 74 mA at 5V DC (±5%), and the isolation voltage is 1500V AC RMS. Power dissipation ranges from 0.4 W to 8.1 W, with thermal dissipation from 1.3 BTU/hr to 27.7 BTU/hr. The operating temperature range is 0 to 60 °C (32 to 140 °F).
Industry Applications
The 1771-IH is ideal for applications requiring reliable DC input sensing, such as:
- Monitoring limit switches and proximity sensors in automated assembly lines.
- Reading discrete status signals from motor control centers.
- Interfacing with push-button and selector switch inputs in control panels.
Its wide voltage range and sink configuration make it compatible with many industrial DC power supplies. When upgrading legacy PLC 5 systems, the 1771-IH provides a drop-in solution that maintains system integrity while offering dependable performance.
Installation & Setup
Mount the 1771-IH in any available slot of a 1771 I/O chassis. Ensure the backplane connector aligns properly and secure the module in place. Connect field wiring using the 1771-WA wiring arm (or 1771-WD if specified). Verify that the DC supply voltage is within the 24–48V range and that the input signals meet the sink configuration requirements. After installation, power up the system and check the status indicators to confirm proper operation.
Maintenance & Reliability
Routine inspection includes checking for loose wiring, verifying that the module is seated correctly, and ensuring that the operating environment stays within the specified temperature range. Because the 1771-IH is an earlier model, regular monitoring of input signal integrity can help prevent unexpected downtime. Keeping spare modules on hand minimizes production interruptions.
Compatibility & Integration
The 1771-IH is designed for use with Allen-Bradley PLC 5 processors and the Bulletin 1771 I/O system. It is rack-mountable and uses the standard 1771 backplane interface. The module works with the 1771-WA wiring arm (or 1771-WD) for field wiring connections. No additional communication protocols are required; it operates as a standard I/O module within the PLC 5 architecture.
Selection Guide & Purchasing Advice
Before purchasing, verify that the 1771-IH meets your input voltage and sink/source requirements. Confirm that your chassis has an available slot and that the wiring arm matches your field wiring configuration. PLC Source PRO offers genuine Allen-Bradley 1771-IH modules with reliable availability. Ensure you order the correct module for your system to avoid compatibility issues.