The 1791D-8V8P, manufactured by Allen Bradley of Rockwell Automation is a CompactBlock I/O module, which belongs to the 1791D family of I/O modules. This device has a built-in DeviceNet I/O adapter, a built-in power supply and various I/O circuitry. It is NEMA Type 1+ certified, meaning that it is compatible with many different types of sensors. The compact size of the device enables it to be placed in small spaces near a sensor or an actuator where there are many distributed I/O blocks.

The 1791D-8V8P features a 10 to 30 Volt DC built-in power source which helps the device to adapt to a large range of voltages and power supplies coming from the network. It has a feature that protects it from the output and short-circuits. The 1791D-8V8P additionally has a feature that automatically detects and matches the system baud rate to prevent crashes caused by an incorrect baud rate setting. Moreover, it has switches on a notary node address that aid in reducing the node commissioning time. Module communication is easily possible with any SLC, PLC, or SoftLogix controller, and data exchange is possible in 3 modes, which are viz. cyclic, polled, and change-of-state. The change-of-state mode of operation helps increase the throughput of the network by reducing the bandwidth usage. It also provides the option of changing the input filters from “off” to “on” and from “on” to “off” delay conditions to best suit the needs of a specific application.

To connecting the inputs and outputs, it is advised to use an external DC 24 Volt power source, independent of the network. The 1791D-8V8P can be easily mounted in an enclosed panel or a DIN rail in both horizontal and vertical positions. Operation of the device is advised within the temperature range of 0 to 60 degrees Celsius. When making any type of connection to the module, use a stranded 14 Gauge copper wire with a 3/64 inch maximum insulation.