Allen-Bradley 1790D-T8A0 | 8-Channel 120V AC Input Module
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Allen-Bradley 1790D-T8A0 - 8-Channel 120V AC Input Module
Directly interface with industrial power signals using the Allen-Bradley 1790D-T8A0. This specialized ArmorBlock module provides 8 digital inputs designed for 110V AC circuits, allowing you to monitor line-voltage devices like contactor auxiliaries, limit switches, and selector switches directly on your DeviceNet network. With built-in status LEDs and robust isolation, it safely bridges high-voltage field devices to low-voltage control networks.
Key Advantages
- Direct High-Voltage Sensing: Connects directly to 110V AC field devices without needing intermediate relays or voltage converters, simplifying wiring and saving panel space.
- Robust & Safe Isolation: Features 1250V AC photocoupler isolation, protecting your sensitive DeviceNet network and logic from high-voltage transients and noise on the AC lines.
- Clear Status Indication: Eight individual green LEDs provide immediate visual feedback on the state of each AC input, facilitating quick diagnostics.
- Easy Installation: Screw terminal block allows for secure and straightforward wiring of standard AC power conductors.
Complete Technical Specifications
Brand & Series: Allen-Bradley ArmorBlock (1790 Series)
Full Model Number: 1790D-T8A0
Module Type: 8-Point 120V AC Digital Input Module
Input Voltage: 85V AC to 132V AC (110V AC Nominal, 47-63 Hz)
On-State Current: 9 mA maximum @ 132V AC
Input Impedance: 18 kΩ
Switching Threshold: ON: >85V AC, OFF: <45V AC
Response Time: Turn-ON delay: 10 ms, Turn-OFF delay: 30 ms
Status Indicators: 8 individual Green LEDs (one per input channel)
Common Groups: 1 point per common (8 independent commons)
DeviceNet Logic Power: 24V DC (11V to 28.8V DC)
External AC Power: 110V AC, 60 Hz (85-132V AC, 47-63 Hz range) – Powers the input sensing circuitry.
Electrical Isolation: 1250V AC RMS (AC Inputs to internal logic)
Wiring Connection: Screw Terminal Block (M3.0, 7 lb-in maximum torque)
Recommended Fuse: 1 A, 250V, normal blow (per input circuit or group)
Wire Compatibility: Copper or copper-clad aluminum conductors.
Installation & Wiring Guide
Mount the 1790D-T8A0 module on a DIN rail. Provide both 24V DC for DeviceNet logic and a separate 110V AC supply for the input circuits. Wire your AC field device (e.g., a normally-open contact from a motor starter) in series with the AC hot line and the module's input terminal. Connect the AC neutral/common to the module's corresponding common terminal. Each input has its own independent common, allowing connection to different AC phases or sources. Install the recommended 1A fuse in series with each input for protection.
Package & Warranty
What's Included: 1 x Allen-Bradley 1790D-T8A0 120V AC Input Module with terminal block.
Our Guarantee: This high-voltage interface module is covered by a solid 12-month warranty.
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Frequently Asked Questions (FAQ)
Can this module be used with 240V AC signals?
No. The maximum rated input voltage is 132V AC. Applying 240V AC will damage the module. For higher voltages, use an interposing relay or a voltage divider designed for the specific voltage.
Why are the response times slower than DC input modules?
The AC input circuit must rectify and filter the signal to detect its presence, which inherently takes more time. The 10-30 ms response is perfectly adequate for monitoring contactors, switches, and other electromechanical devices.
Does it require a neutral wire for each input?
Yes. Since each input has an independent common, you need to connect the return path (neutral) for each AC circuit you are monitoring to its specific common terminal on the module.
Can I mix inputs from different AC phases?
Yes, because each input is independently isolated via the photocoupler and has its own common terminal. You can monitor devices on different phases, but you must ensure the correct neutral for each phase is connected to the corresponding common.
What is the external 110V AC power supply used for?
This supply powers the internal circuitry (like the photocoupler's LED side) that senses the presence of the AC field signal. It is separate from the field AC voltage you are monitoring.
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