Allen-Bradley 1790D-0W6 6-Point Relay Output Base

Allen-Bradley 1790D-0W6 24V DC 6-Relay Output Module

Product Introduction

The 1790D-0W6 belongs to the 1790 Compact I/O series from Allen‑Bradley. This module provides 6 relay outputs with Form A (normally open) contacts. Each relay supports resistive loads up to 2.0 A at 30V AC or 28.8V DC. You can use it with mixed AC and DC field devices. Unlike solid-state outputs, relays offer true dry contact switching. Moreover, the 1790D-0W6 isolates each output with its own common terminal. Therefore, it suits applications requiring separate load circuits or different voltage levels.

Technical Specifications

Output Characteristics (Relay)

• Relay type: Form A, normally open, single pole single throw (SPST)

• Output voltage range:

  • 5…28.8V DC @ 2.0 A (resistive)

  • 30V AC @ 2.0 A (resistive)

• Output current rating: 2.0 A at rated voltage (resistive load)

• Minimum load: 100 µA, 100 mV DC

• On-state voltage drop: 0.5V max @ 2.0 A, resistive load, 24V DC

• Initial contact resistance: 30 mΩ

• Expected contact life:

  • 300,000 cycles (resistive load)

  • 100,000 cycles (inductive load)

• Off-state leakage: 1.5 mA max

• Output delay time: Off to On ≤ 10 ms max, On to Off ≤ 10 ms max

• Indicators: 6 green LEDs (one per relay)

• Common type: 1 point per 1 COM (each relay isolated)

Field Power and Isolation

• Field power supply voltage: 24V DC nominal (range 19.2…28.8V DC)

• Field power dissipation: 10 mA @ 28.8V DC per channel

• Isolation: I/O to logic via photocoupler

• Isolation voltage: 1250V AC rms

• Wiring connection: 37‑pin D‑shell connector

DeviceNet Base Power

• Supply voltage: 24V DC nominal

• Voltage range: 11…28.8V DC

• Power dissipation: 1.2 W max @ 28.8V DC

Relay Contact Life Considerations

The 1790D-0W6 provides 300,000 cycles for resistive loads. For inductive loads like solenoids or small motors, the life drops to 100,000 cycles. Add a flyback diode (for DC) or an RC snubber (for AC) to extend contact life. This protects the relay from voltage spikes. Additionally, avoid switching loads above 2.0 A to prevent contact welding.

Mechanical and Environmental Data

• Mounting: DIN rail (35 mm)

• Dimensions: 118 mm (H) x 87 mm (W) x 54 mm (D)

• Operating temperature: 0 to 55 °C

• Storage temperature: –40 to 85 °C

• Relative humidity: 5 to 95% non‑condensing

• Vibration resistance: 5 g @ 10–500 Hz

• Shock resistance: 30 g

Frequently Asked Questions (FAQ)

1. Can the 1790D-0W6 switch both AC and DC loads on the same module?
Yes. The 1790D-0W6 supports AC (30V max) and DC (28.8V max) loads. However, each relay is isolated with its own COM. You can mix AC and DC on different channels without interference.

2. What happens if I exceed the 2.0 A contact rating?
Exceeding 2.0 A may weld the relay contacts or reduce the expected life dramatically. Use an external contactor or intermediate relay for higher current loads.

3. Why is the off-state leakage 1.5 mA for a relay output?
The 1.5 mA leakage comes from the internal snubber or protection circuit across the contacts. This is normal for relay modules with transient suppression. It will not energize most loads.

4. How do I extend the contact life for inductive loads?
For DC inductive loads, add a flyback diode in parallel with the load. For AC inductive loads, add an RC snubber across the contacts. This reduces arcing and protects the 1790D-0W6 relays.

5. Does each relay have a separate common terminal?
Yes. The 1790D-0W6 provides 1 COM per point. This means all 6 relays are fully isolated from each other. You can connect different voltages or even mix AC and DC freely.