1790-T8A0X Allen-Bradley 120V AC Input Module

1790-T8A0X CompactBlock LDX Digital Input Expansion Module

Product Introduction

The 1790-T8A0X module belongs to the Allen‑Bradley CompactBlock LDX family. This digital input expansion module operates with 120 Volts AC input voltage and provides 8 non‑isolated input points. Moreover, it includes a DeviceNet communication port for seamless integration with PLC, SLC, Logix, or SoftLogix controllers via DeviceNet scanner modules. The module features a NEMA Type 1 enclosure and fixed screw‑type terminals. Eight green LED indicators show the status of each input channel. Designed for low‑cost and space‑constrained applications, the 1790-T8A0X delivers reliable AC input expansion.

Technical Specifications

Input Characteristics
The 1790-T8A0X offers 8 non‑isolated AC input points. These inputs share a common configuration of 8 points per 8COM.

• Number of inputs: 8 points (non‑isolated)

• On‑state voltage range: 85V AC (min) / 110V AC (nom) / 132V AC (max)

• Off‑state voltage: 45V AC max

• On‑state current: 9 mA max at 132V AC

• Input impedance: 18 kiloohms

• Input signal delay: Off to On = 10 ms max; On to Off = 30 ms max

• Indicators: 8 green LEDs for input status

• Common type: 8 points share 8COM

Power and Isolation

• DeviceNet supply voltage: 24V DC nominal (range 11…28.8V DC)

• DeviceNet power dissipation: 1.2 W max at 28.8V DC

• External AC power supply: 110V RMS, 60 Hz (range 85…132V RMS, 47…63 Hz)

• External AC power dissipation: 3 W at 132V AC

• Isolation (I/O to logic): Photocoupler isolation, 1250V AC RMS

• Field power: Non‑isolated

• Recommended fusing: 1 A, 250V, normal blow

Mechanical & Environmental

• Enclosure type: NEMA Type 1

• Wiring: Fixed screw terminals (M3.0), torque 7 lb‑in max

• Conductor material: Copper or copper‑clad aluminum

• Weight: 0.14 kg (0.31 lbs)

Configuration and Compatibility

You can configure the 1790-T8A0X module using two methods. First, use the rotary switches directly on the device for node address setting. Alternatively, employ embedded ESD files for software‑based configuration. This module works with both digital and analog base modules for I/O expansion. Furthermore, it communicates with Allen‑Bradley programmable controllers through DeviceNet scanner modules. The 1790-T8A0X is compatible with NEMA/UL Type 1 AC modules, making it suitable for industrial control panels.

Installation Guidelines

First, mount the 1790-T8A0X on a standard DIN rail inside a NEMA Type 1 enclosure. Ensure adequate clearance for wiring and ventilation. Next, connect the 24V DC DeviceNet power supply to the designated terminals. Then, wire the external 110V AC power supply to power the input circuits. After that, connect your AC field devices (such as limit switches or pushbuttons) to the 8 input terminals.

Additionally, install a 1 A, 250V normal blow fuse on the AC line for protection. Tighten all M3.0 screw terminals to 7 lb‑in maximum. Finally, power up the system and verify the green LED indicators. Do not apply power while wiring to avoid electric shock.

Packaging List

• 1 x 1790-T8A0X digital input expansion module

• 1 x fixed screw terminal block (pre‑attached)

• 1 x quick start guide (printed)

Shipping

We ship worldwide via FedEx, UPS, or DHL. Tracking number provided after dispatch.

Frequently Asked Questions (FAQ)

1. What type of field devices can I connect to the 1790-T8A0X?
You can connect AC field devices such as pushbuttons, limit switches, proximity sensors, and selector switches that operate at 85…132V AC. The 1790-T8A0X accepts 8 non‑isolated AC inputs.

2. Does this module require an external AC power supply?
Yes. The 1790-T8A0X needs a separate 110V AC external power supply (85…132V AC, 47…63 Hz) for the input circuits. Additionally, you must provide a 24V DC supply for DeviceNet communication.

3. Is the 1790-T8A0X compatible with Logix controllers?
Absolutely. This module communicates via DeviceNet and works with Allen‑Bradley PLC, SLC, Logix, and SoftLogix controllers when paired with a suitable DeviceNet scanner module.

4. What is the signal delay for the inputs?
The 1790-T8A0X has an off‑to‑on signal delay of 10 milliseconds maximum and an on‑to‑off delay of 30 milliseconds maximum. These delays are typical for AC input modules due to the input filtering.

5. Do I need a fuse for the AC line protection?
Yes. Allen‑Bradley recommends using a 1 A, 250V normal blow fuse on the AC line. The 1790-T8A0X does not include an internal fuse, so external fusing is required for safety.