Allen-Bradley 1794-ACNR ControlNet Adapter Module

1794-ACNR Allen-Bradley Flex I/O Redundant Adapter

Product Introduction

The 1794-ACNR module from Allen-Bradley is a dedicated ControlNet adapter that serves as the backbone interface for the Flex I/O distributed system. This adapter facilitates seamless communication between the controller and up to eight discrete, analog, or specialty I/O modules. It specifically enables a redundant media topology, which significantly enhances network reliability for critical processes. Additionally, its robust design allows for operation in harsh industrial environments with extreme temperatures.

For instance, this adapter processes input data from field devices and delivers output commands from the controller with minimal latency. It uses the proven ControlNet protocol to ensure deterministic performance. The dual BNC ports on the 1794-ACNR permit connection to both the primary and secondary ControlNet trunks. This configuration supports a fail-safe architecture without requiring complex external switches. The module is powered by an external 24V DC supply and draws a maximum current of 400 mA.

Key Technical Specifications

This communication adapter includes several vital parameters for proper system design. First, it offers a Communication Rate of 5 Mbps over each of its two ports. The module’s Input Voltage Range is between 19.2 to 31.2 Volts DC, with a nominal rating of 24 Volts DC. Furthermore, it handles an Inrush Current of 23A for 2 milliseconds. The Flexbus Output Current, which powers the connected I/O modules, can reach a maximum of 640 mA at 5 Volts DC.

The 1794-ACNR also includes visual diagnostics through its built-in LED indicators. Specifically, it features two Communication LEDs (Comm A and Comm B) and a single I/O status LED, all displaying red or green states. Additionally, the electrical isolation is robust, with an Isolation Voltage of 850 Volts DC tested for 60 seconds. The power consumption is 400mA from an external 24V supply. Finally, the module complies with ControlNet Protocol V 1.25 for interoperability.

Mechanical and Environmental Ratings

Environmental Limits

The 1794-ACNR is built to withstand demanding industrial conditions. For ambient temperature, its Operating Temperature ranges from -20 to 55 °C (-4 to 131 °F), with a maximum Surrounding Air Temperature of 55 °C. It also survives non-operating temperatures between -40 and 85 °C. Moreover, it operates reliably in 5 to 95% non-condensing relative humidity.

Mechanical Stress Tolerance

This adapter is exceptionally durable against physical stress. It meets the IEC 60068-2-27 standard for Operating Shock, enduring 30 g of shock. In addition, its Vibration tolerance is rated at 5 g @ 10 to 500 Hz per IEC 60068-2-6. It also withstands a non-operating shock of 50 g. Consequently, the 1794-ACNR remains stable in applications with high vibration, such as pumping stations or material handling systems.

Power and Thermal Management

Efficient power management is crucial for the 1794-ACNR. Its Power Dissipation is rated at 4.6W maximum @ 19.2V dc. Correspondingly, its Thermal Dissipation is 15.7 BTU/hr @ 19.2V dc. Therefore, this module generates moderate heat that must be accounted for in the panel design. Users should ensure adequate airflow around the DIN rail to maintain the surrounding temperature within the specified limit.

Installation Guidelines

Mounting Options

Primarily, the 1794-ACNR is designed for DIN Rail mounting. However, it also supports panel mounting for flexible installation. Its compact dimensions, measuring 3.7 x 3.6 x 3.4 inches, help it fit neatly in crowded cabinets. Remember that the adapter has an open-type enclosure. Hence, it requires an appropriate IP-rated cabinet for protection against dust and direct contact.

ControlNet and Flexbus Connections

For network connections, the adapter uses two ControlNet BNC ports. Users must connect these to a Belden RG-6/U ControlNet cable with 12 AWG stranded conductors. Furthermore, the module connects to the Flex I/O system via the terminal base units. It supports a maximum of eight terminal bases and thus a maximum of eight I/O modules. The power supply must be a Safety Extra Low Voltage (SELV) or Protected Extra Low Voltage (PELV) type to comply with CE directives.

Packaging and Shipping Information

All units of the 1794-ACNR are carefully packaged to prevent static or physical damage. The package includes the adapter module itself. However, the packaging does not include installation manuals, mounting hardware, or terminal base units. We professionally pack the module in anti-static material and secure it for shipping. The shipping weight is approximately 0.45 kg (1.0 lb).

• Shipping Carriers: FedEx, UPS, DHL

• Warranty and Certificates: Not included in the package

Frequently Asked Questions (FAQ)

1. Can the 1794-ACNR support standard analog modules?
Yes, this adapter supports up to eight Flex I/O modules, including discrete, analog, and specialty modules. It communicates with all standard 1794 I/O types.

2. Is the 1794-ACNR suitable for a redundant network?
Absolutely. Its primary design is for redundant ControlNet media. It features two independent BNC ports for connecting to separate trunk lines for high availability.

3. What cable type does the 1794-ACNR require for the ControlNet?
It requires a Belden RG-6/U ControlNet cable. This is a 3.31 mm² (12 AWG) stranded cable with a maximum insulation of 1.2 mm.

4. Does the 1794-ACNR need an external power supply?
Yes. It needs an external supply with a voltage range of 19.2 to 31.2V DC. The power supply must be SELV or PELV certified for safety compliance.

5. How do I know if the 1794-ACNR is functioning correctly?
You can check the status using the three LED indicators: Comm A, Comm B, and I/O Status. They display red or green colors to indicate communication activity and faults.