Purchase now: Allen Bradley 1746-IG16 TTL Input Module
Purchase now: Atlantechdrives provides you the 1746-IG16, a specialized 16-channel digital input module manufactured by Allen Bradley for the SLC 500 automation platform. Unlike standard industrial voltage modules, the 1746-IG16 is specifically designed to handle 5V DC TTL (Transistor-Transistor Logic) level signals. This makes it an indispensable asset for facilities that need to interface their rugged SLC 500 PLCs directly with sensitive electronic circuits, custom printed circuit boards (PCBs), absolute encoders, bar code readers, or specialized 5V measurement equipment. By providing a direct TTL interface, engineers can avoid the complexity and latency of using external signal converters or relays, ensuring lightning-fast response times for critical logic operations.
Technical Specifications of the 1746-IG16
The 1746-IG16 module is engineered for high-speed, low-voltage applications. Because TTL signals operate on very tight voltage thresholds, this module features precise detection circuitry to differentiate between logical «High» and «Low» states without misinterpretation. It fits seamlessly into any standard 1746 chassis and integrates perfectly with RSLogix 500 programming software.
- Part Number: 1746-IG16
- Module Type: TTL Digital Input Module
- Compatible System: Allen Bradley SLC 500
- Number of Channels: 16 Points
- Voltage Category: 5V DC TTL Logic
- Operating Voltage Range: 4.5…5.5V DC
- Input Voltage (High): 2.0 to 5.5V DC
- Input Voltage (Low): 0 to 0.8V DC
- Signal Delay (Max): On: 0.25 ms, Off: 0.50 ms (Extremely fast)
- Backplane Current Draw: 140 mA at 5V DC
Installation Advice: Managing Electrical Noise in TTL Systems
TTL logic is highly susceptible to electromagnetic interference (EMI) because the voltage differential between a logic «0» and a logic «1» is minimal. Expert Tip: When wiring the 1746-IG16, it is absolutely critical to use high-quality, shielded twisted-pair cables for all field connections. The shield must be grounded at one end only (typically at the chassis ground) to prevent ground loops. Furthermore, you must route the TTL input cables in completely separate conduits from high-voltage AC lines (like 120V, 240V, or 480V motor feeds). Failure to isolate these low-voltage lines will result in induced noise, causing the PLC to read false positive inputs and leading to erratic machine behavior.
Maintenance and System Integration
Maintaining the 1746-IG16 requires strict attention to the external 5V DC power supply providing the TTL signals. If this supply fluctuates outside the strict 4.5V to 5.5V DC window, the module may fail to register inputs correctly. Periodically check the external power supply with a calibrated oscilloscope to ensure the 5V rail is stable and free of voltage ripple. Additionally, keep the control cabinet free of conductive dust that could bridge the low-voltage terminals.
Frequently Asked Questions (FAQs)
Q: What is the response time of the 1746-IG16 compared to standard DC modules?
A: The 1746-IG16 is significantly faster. It has an ON delay of just 0.25 milliseconds, compared to the 8.0 milliseconds typical of 24V or 48V DC modules, making it perfect for high-speed counting or rapid logic execution applications.
Q: Can I use this module to read standard 24V DC sensors?
A: No. Applying 24V DC to the input terminals of the 1746-IG16 will instantly destroy the module’s sensitive TTL internal circuitry. It is strictly designed for 5V DC logic levels.
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When interfacing with TTL logic, ensure this module is protected within an 1746-A4 industrial chassis.
