Acceptance testing IO modules for Knighton

We have taken delivery of the main IO modules for the Knighton Crossing Project.

The project has selected a 32-channel combined input/output board and a 16-channel combined input/output board to provide relay-driven IO and optoisolated inputs over Modbus. This is then sent over ethernet (Modbus-TCP) via an adapter module. We are trialling a new compact adapter (available here - make sure to select the RS485 option not the default RS232!) which, similar to the existing unit at Sleaford East, is also DIN rail mountable. The only noticeable difference apart from size is that the connections are compact push-fit, not screw terminal, so this will limit the wire gauge that can be used.

The two IO modules have been successfully tested using both a USB to RS485 adapter and the ethernet adapter we intend to provide for the installation. By using ethernet these modules can be easily distributed around a museum or layout. We have even sourced a Modbus adapter which goes straight to WiFi, but this has not been required so far. This could be useful for a location case or ground frame where it would be costly to install a multicore cable, but where power is available.

Our Modbus IO software module for the openSignalBox simulator framework is nearing completion, and we will be testing it using these boards and a software simulator first, before rolling it out to Sleaford East for further testing. Then these boards will be shipped to Knighton Crossing Project for integration into their electrical prototyping.

The photo below shows the two modules as delivered.

The following photo shows the 16-channel module under test, using the small Modbus ethernet adapter.

Finally, the new Modbus adapter against the previous one. Both adapters perform the same job and are similar prices, so the larger screw terminals may mean that the larger unit is still a better choice depending on the application.