Product Overview
The Allen-Bradley 1790-T8A0X CompactBlock LDX I/O digital input expansion module offers a cost-effective solution for expanding I/O capacity in industrial automation systems. Its compact form factor reduces installation costs while maintaining robust performance.
Technical Specifications Breakdown
Key parameters for the 1790-T8A0X are listed below for quick reference:
| Feature | Specification |
|---|---|
| Inputs per Module | 8 points nonisolated |
| On-State Voltage Range | 85V ac min, 110V ac nom, 132V ac max |
| Input Impedance | 18 kΩ |
| On-State Current | 9 mA max @ 132V ac |
| Off-State Voltage | 45V ac max |
| Input Signal Delay | Off to On: 10 ms, On to Off: 30 ms |
| Indicators | 8 green input status |
| Common Type | 8 points/8 COM |
| External AC Power Supply | Supply voltage - 110V rms, 60 Hz; Voltage range - 85…32V rms, 47…63 Hz; Power dissipation - 3 W @ 132V ac |
| DeviceNet Power (Base Module) | Supply voltage - 24V dc nom; Voltage range - 11…28.8V dc; Power dissipation - 1.2 W max @ 28.8V dc |
| Isolation | I/O to logic: photocoupler isolation; Isolation voltage: 1250V ac rms/V ac; Field power: non-isolation |
| Wiring | Terminal block (M3.0); screw torque: 7 lb-in max (use copper or copper-clad aluminum conductors) |
| Recommended Fusing | 1 A, 250V, normal blow |
| Enclosure Type | NEMA Type 1 |
| Weight | 0.31 lbs (0.14 kg) |
Industry Applications
For example, in packaging lines, the 8 non-isolated inputs can monitor limit switches or proximity sensors, while the DeviceNet interface enables centralized control without excessive wiring. The compact design reduces panel space requirements, lowering overall enclosure costs. In material handling systems, the module's fast signal delay (10 ms off-to-on) ensures quick response to conveyor jams or part presence, minimizing downtime.
Installation & Setup Guidance
Mount the module in a NEMA Type 1 enclosure to protect against dust and light moisture. Use copper or copper-clad aluminum conductors for wiring, and tighten terminal screws to a maximum of 7 lb-in. Connect the external AC power supply (110V rms, 60 Hz) to power the inputs, and ensure the DeviceNet base module provides 24V dc nominal for communication. Configure the module using rotary switches or embedded ESD files for node address and baud rate. Always verify that the input voltage stays within the 85 to 132V ac range to avoid damage.
Maintenance & Reliability
Periodically inspect the LED indicators (8 green input status lights) to confirm proper operation. Check terminal connections for tightness annually, as vibration can loosen screws. Keep the enclosure clean and free of conductive debris. The module's photocoupler isolation (1250V ac) protects logic circuits from field-side surges, enhancing long-term reliability. Replace the recommended 1 A, 250V normal blow fuse if it opens, using only specified ratings.
Compatibility & Integration
The 1790-T8A0X communicates via DeviceNet, a device-level network. It works with Allen-Bradley PLC, SLC, Logix, or SoftLogix controllers through DeviceNet scanner modules. Use it for I/O expansion with both digital and analog base modules. The embedded ESD files simplify configuration in RSLogix or similar software.
Selection Guide & Purchasing Advice
When selecting this module, consider your input count and voltage requirements. The 8 non-isolated inputs suit applications where common grounding is acceptable. For isolated needs, explore other CompactBlock LDX variants. AutoDCSTech stocks the 1790-T8A0X and can advise on lifecycle status. Please verify current availability before ordering.
Troubleshooting & Common Issues
If inputs fail to register, check the external AC power supply (110V rms) and ensure the on-state voltage is at least 85V ac. Verify that the DeviceNet network is powered and configured correctly. If the green LED indicators are off, inspect the fuse (1 A, 250V) for continuity. Signal delays longer than 10 ms off-to-on may indicate wiring issues or incorrect configuration. For persistent problems, consult the module's documentation or contact AutoDCSTech support.
Availability & Condition at AutoDCSTech
| Part Number | 1790-T8A0X |
|---|---|
| Availability | In Stock |
| Condition | New |
| Warranty | One Year |
| Origin | US |
