Driving Relays Connected to the NI 6518 with External Power

Hardware: Digital I/O (DIO), Digital I/O (DIO)>>Isolated>>PCI-6518

Problem:
Can the output terminals of the NI PCI-6518 supply enough power to drive a relay? If then can, do I need to provide an external power supply for the output terminals on the board?

Solution:
Yes. The power at the input and output connectors of the NI-6518 must be provided by the user. The maximum source voltage that the output pin of a 6518 can provide is 30V DC. To connect your relay to the output pin of the 6518, follow these steps:

Connect a power supply in the range of 5V to 30V DC (depending on how much power you need) between VCC (pins 10, 28, and 29) and OUT.COM (GND) (pin 19). Refer to the image attachments below.
Connect the relay to your output terminal. Make sure that the relay can accept voltages between 5V and 30V DC and needs no more than 350 mA to change states.
If the relay you are planning to connect needs more than 75 mA but less than 350 mA to be able to change states, make sure you use only 1 output channel. (Output channels are located on Ports 2 and 3 which belong to the same bank).

Note: The maximum current that the 6518 can source is 350 mA. This maximum current is available ONLY if 1 output line on each bank is being used. Since all the output channels of the 6518 belong to the same bank, only 1output channel can be used if the desired source current is 350 mA (the 6518 has 2 banks. Ports 0 and 1, which make up the inputs of the 6518, belong to one bank while Ports 2 and 3, which make up the output pins, belong to another bank). If more than 1 output line is being used, the maximum source current that each output line on the 6518 can supply is 75 mA.

Report Date: 12/13/2004
Last Updated: 05/05/2006
Document ID: 3GCGEU6K

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