Product Introduction
The Allen-Bradley 1756-IG16 is a ControlLogix digital DC input module engineered for precise TTL-level signal acquisition. As part of the ControlLogix family, this module provides 16 input points (9 per common) and operates on a 5V DC TTL source with a low-true logic format. Designed for industrial environments, the 1756-IG16 ensures reliable detection of digital signals in applications such as high-speed counting, position sensing, and logic interfacing.
This module uses a removable terminal block (RTB) for wiring, compatible with the 1756-TBNH and 1756-TBSH housings. The TTL inputs are inverted, meaning a low voltage (0.2 to 0.8V DC) represents the true (ON) state, while a high voltage (2.0 to 5.5V DC) guarantees the OFF state. This characteristic makes the 1756-IG16 ideal for systems that use active-low signals.
Technical Specifications
The following table outlines the key specifications of the Allen-Bradley 1756-IG16:
| Specification |
Value |
| Manufacturer |
Rockwell Automation |
| Brand |
Allen-Bradley |
| Part Number |
1756-IG16 |
| Series |
ControlLogix |
| Module Type |
Digital DC Input Module |
| Inputs |
16-points (9 per common) |
| Input Voltage |
5 Volts DC with TTL Source |
| Operating Voltage Range |
4.5-5.5 Volts DC |
| Input Delay Time |
0.25 milliseconds plus selected filter time |
| Maximum Input Current, Off-State |
4.1 milliamps |
| Power Dissipation (Max) |
1.4 Watts at 60 degrees Celsius |
| Backplane Current at 5 Volts |
110 milliamps |
| Removable Terminal Block(s) |
1756-TBNH, 1756-TBSH |
| UPC |
10612598171290 |
The module's operating voltage range of 4.5 to 5.5V DC ensures compatibility with standard 5V TTL logic. The maximum input current of 4.1 mA at off-state prevents false triggering, while the input delay time of 0.25 ms plus filter time allows for noise rejection in industrial settings.
Industry Applications
The 1756-IG16 excels in applications requiring high-speed digital input reading. Common use cases include:
-
Machine Control: Monitor limit switches, proximity sensors, and photo eyes in automated assembly lines.
-
Process Monitoring: Read discrete signals from pressure switches, flow meters, and level sensors.
-
High-Speed Counting: Capture fast pulses from encoders or flow meters, leveraging the low input delay.
Because the module uses TTL low-true logic, it is particularly suited for systems that already operate with 5V active-low signals, reducing the need for signal conditioning.
Installation & Setup Guidance
Installing the 1756-IG16 requires a ControlLogix chassis and a compatible removable terminal block (RTB). Follow these steps:
- Insert the module into any available slot in the ControlLogix chassis. Ensure the chassis is powered off during installation.
- Attach the RTB (1756-TBNH or 1756-TBSH) to the module's front connector, aligning the keying features.
- Wire the input signals to the RTB terminals, observing the polarity for TTL inputs. The low-true format means that a low voltage (0-0.8V) corresponds to ON, so connect the signal accordingly.
- Configure the module in your RSLogix 5000 or Studio 5000 environment, setting the appropriate filter times (0, 1, or 2 ms) based on your signal characteristics.
- Power up the chassis and verify the input status via the module's diagnostic LEDs or the controller's I/O tree.
Always consult the ControlLogix installation instructions for torque specifications and wiring guidelines.
Maintenance & Reliability
The 1756-IG16 is designed for long-term reliability, but routine checks can extend its service life. Inspect the module periodically for dust accumulation on the RTB connections, which can cause intermittent signals. Verify that the backplane current draw remains within the specified 110 mA at 5V to avoid overloading the chassis power supply. The maximum power dissipation of 1.4W at 60°C indicates that proper ventilation in the control cabinet is essential. Regular thermal inspections help prevent overheating, which could degrade performance over time.
Compatibility & Integration
The 1756-IG16 integrates seamlessly with the ControlLogix platform, including 1756-L6x, L7x, and L8x controllers. It communicates over the ControlLogix backplane, which supports both scheduled and unscheduled data exchange. The module is compatible with RSLogix 5000 and Studio 5000 software. For wiring, it uses the 1756-TBNH or 1756-TBSH terminal blocks, which are sold separately. No special communication modules are required, as the backplane provides power and data transfer.
Selection Guide & Purchasing Advice
Before purchasing the Allen-Bradley 1756-IG16, verify your system's input voltage and logic requirements. This module is specifically for 5V DC TTL low-true signals; other input types (e.g., 24V DC) require different modules. Confirm the number of input points needed and ensure your chassis has an available slot. Also, decide whether you need the 1756-TBNH or 1756-TBSH terminal block, as these are not included with the module. For reliable supply and competitive pricing, consider PLC Source PRO as your sourcing partner for genuine Allen-Bradley parts.