Configuring Current Limits for the NI 9478 (FPGA Interface)

You can configure the active current limit for each channel and the current limit thresholds at edit time using the C Series Module Properties dialog box. You can programmatically change these settings at run time using the FPGA I/O Property Node. The execution of an I/O Property Node that is configured with a Current Limit property overwrites the value you configured in the C Series Module Properties dialog box.

Configuring Current Limits Using the C Series Module Properties Dialog Box

Complete the following steps to configure the active current limit for each channel and the current limit thresholds for the NI 9478 using the C Series Module Properties dialog box.

1. Configure the CompactRIO system, and add an NI 9478.
2. Right-click the NI 9478 in the Project Explorer window and select Properties from the shortcut menu to display the C Series Module Properties dialog box.
3. Select the channel(s) for which you want to configure the active current limit from the Channels table. You can select more than one channel by holding the <Ctrl> or <Shift> key when selecting channels.
4. Select the active current limit for the channel(s) from the Active Limit pull-down menu.
5. Enter a value between 0 and 5.1 in the Current Limit text box that corresponds to the active current limit for the selected channel(s).
6. Place a checkmark in the Enable Overcurrent Refresh checkbox and set the time in the Overcurrent Refresh Period text box if you want to enable a channel to automatically recover if the channel exceeds its active current limit threshold.
7. Click the OK button.
8. Select File»Save All in the Project Explorer window.

Configuring Current Limits Using the FPGA I/O Property Node

Complete the following steps to configure the active current limit for each channel and the current limit thresholds using the FPGA I/O Property Node.

1. Place three FPGA I/O Property Nodes on the block diagram and configure them for the NI 9478.
2. Click the Property section on the first Property Node and select the Active Current Limit property from the shortcut menu.
3. Right-click the Active Current Limit input and select Create»Control from the shortcut menu.
4. On the front panel of the VI, select the active current limit for each channel from the Active Current Limit array.
5. Click the Property section on the second Property Node and select the Current Limit A property from the shortcut menu.
6. Right-click the Current Limit A input and select Create»Control from the shortcut menu.
7. Click the Property section on the third Property Node and select the Current Limit B property from the shortcut menu.
8. Right-click the Current Limit B input and select Create»Control from the shortcut menu.
9. On the front panel of the VI, enter binary values in the Current Limit controls to set the current limit thresholds. You can use the following equation in the host VI to calculate the binary value from amperes:
   Binary Value = (Current Value / 5.12 A) × 256