Current Draw of NI Controllers

Issue Details

I am using an NI Industrial Controller (IC), CompactRIO (cRIO), or CompactDAQ (cDAQ) and am selecting the wiring to use to power my device. How much current can I expect the device to draw so that I can adequately select my wiring?

Solution

NI does not specify a typical current draw for our controllers. Rather, we specify the maximum power consumption of our devices. The reason for this is that current draw of the device is dependent on several factors, not limited to:

• Power supply voltage
• Utilization of the CPU
• Number of and types of modules in the chassis (if using a cRIO or cDAQ)
• Amount of I/O channels being used
• Whether you are using Power-Over-Ethernet to power external devices (if using an IC)

The typical power consumption of your controller will likely be much lower than the maximum specified power consumption.

If you need to choose a wire gauge to use for wiring power to your controller, you can choose a wire based on the worst-case scenario for power draw at a given supply voltage. For example, if you are using a 24 V power supply and the maximum power consumption specification for your controller is 150 Watts, then following Ohm's Law, the maximum current draw would be (150 W)/(24 V) = 6.25 A. 

Additional Information

The datasheet for your power supply should also give information about the wiring gauge that is recommended to transmit power from the supply. For example, the manual for the PS-15 power supply recommends using 10-20 AWG wires.