1790D-T8BV8B Allen-Bradley Base Module

1790D-T8BV8B CompactBlock LDX Base Module

Product Introduction

The 1790D-T8BV8B module belongs to the Allen‑Bradley CompactBlock LDX family. It runs on 24 Volts DC field power and integrates 8 non‑isolated inputs and 8 sourcing outputs. Additionally, it features a DeviceNet interface for seamless network connection. LED indicators are available for each I/O point, simplifying troubleshooting. This base module is designed for small to medium distributed control systems. Its compact size saves panel space while delivering reliable performance.

Technical Specifications

Input Characteristics
The 1790D-T8BV8B offers 8 universal inputs. These inputs are non‑isolated and can be used as sinking or sourcing types.

• On‑state voltage: 9.6V DC (min) / 24V DC (nom) / 28.8V DC (max)

• On‑state current: 8 mA max per point at 28.8V DC

• Off‑state voltage: 5V DC max

• Input impedance: 4.8 kiloohms (nominal)

• Common type: 8 points share 8COM (non‑polarity)

• Indicators: 8 green LEDs

Output Characteristics
The module includes 8 non‑isolated sourcing outputs.

• On‑state voltage: 10V DC (min) / 24V DC (nom) / 28.8V DC (max)

• On‑state voltage drop: 0.5V DC max

• On‑state current: 1 mA min per channel

• Off‑state leakage: 0.5 mA max

• Output signal delay: Off→On = 0.5 ms max; On→Off = 1.0 ms max

• Output current rating: 0.5 A max per output, 4.0 A max per common

• Indicators: 8 green LEDs

Power and Isolation

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

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

• Field power supply: 24V DC nominal (range 10…28.8V DC)

• Field power dissipation: 6 mA at 28.8V DC per point

• Isolation voltage: 1250V AC RMS (I/O to logic via photocoupler)

• DeviceNet to logic: non‑isolated

Mechanical & Environmental

• Wiring: Terminal block with M3.0 screws (torque: 7 lb‑in max)

• Weight: 0.14 kg (0.31 lbs)

• Operating temperature: 0…55 °C (32…131 °F)

• Storage temperature: -40…85 °C (-40…185 °F)

• Relative humidity: 5…95% non‑condensing

Installation and Wiring Guidelines

First, mount the 1790D-T8BV8B on a standard DIN rail inside a control cabinet. Ensure proper clearance for ventilation and cable routing. Next, connect the 24V DC field power supply to the designated terminals. Then, wire the input devices (sensors or switches) to the input terminals. For outputs, connect the sourcing loads such as small relays or indicator lights.

Additionally, use the built‑in DeviceNet connector to link the module to your network. Tighten all screw terminals to 7 lb‑in maximum. Finally, verify the LED indicators: green for active inputs/outputs. Do not apply power while wiring to avoid damage.

Packaging List

• 1 x 1790D-T8BV8B base module

• 1 x 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. Can I mix sinking and sourcing devices on the same module?
Yes. The inputs on the 1790D-T8BV8B are non‑polarity. You can connect both sinking and sourcing field devices to the same module without extra components.

2. What happens if I exceed 0.5A per output?
Exceeding 0.5A per output may damage the output channel. Use an external relay or contactor for higher current loads. The 1790D-T8BV8B is not fused internally.

3. Is the 1790D-T8BV8B compatible with other DeviceNet masters?
Absolutely. It follows standard DeviceNet protocol and works with any DeviceNet scanner, including Allen‑Bradley 1756‑DNB or 1770‑KFD.

4. Do I need an external 24V supply for both field and DeviceNet power?
Yes. The 1790D-T8BV8B requires two separate 24V DC supplies: one for DeviceNet communication and one for field I/O. Both ranges are 10…28.8V DC.

5. Are there LED error codes for troubleshooting?
Each input and output has a green LED. If an input is active but the LED is off, check the field wiring. For network issues, monitor the DeviceNet status LED. The 1790D-T8BV8B does not have a separate red error LED.