From Friday, April 19th (11:00 PM CDT) through Saturday, April 20th (2:00 PM CDT), 2024, ni.com will undergo system upgrades that may result in temporary service interruption.
We appreciate your patience as we improve our online experience.
I am using PCI 7342 motion controller and UMI7772. There are 6 relays in my system, which are 24Vdc coil voltage and 37mA coil current for each. Can I use digital output on PCI 7342 through UMI7772 to drive these relays? PCI7342's digital output is 0-5V, 24mA, but through UMI7772, I can get 5-30Vdc, 100mA output. Am I right? I am not sure 100mA is total or for each output.
The 7772 can source 100 mA per digital output line on the eight sourcing DOs. I agree that this not clearly enough specified in the UMI-7772/7774 user manual.
Don't forget that a relay is basically an inductor and therefore the inrush current can be somewhat higher than the rated current. But I don't think that this might cause problems in this application.
In any case you should connect a breakdown diode in parallel with the relay coil to keep off inducted voltage from the 734x outputs, or some other snubber circuitry.
