Dear All, could anyone please confirm my usage of NI 9477 as a relay works or not with following details. It might be too silly question but I am sure it is not posted before and I really cannot afford to burn my modules. I have two worries, one is sink or source connection, another is overcurrent issue.
The Siemens S7-200 is used to control a step motor driver by sending pulses. I need to provide two digital signals to control step motor's rotation direction. So I propose to connect my NI 9477 as a relay switch shown in the graph below (left configuration).
According to the NI 9477 datasheet (attached), I suppose I should connect it as the right configuration as NI 9477 is sinking module. However, current power supply in the control cabinet is wired as left configuration. I am not sure if I can just connect my NI 9477 or I need to adjust the power supply polarity.
Another concern would be the current through NI 9477. It rated at 1A and will be connected in series with only a 24VDC power and s7-200 digital input. I am not sure if the current would be a concern as in s7-200 datasheet, it seems that the current is only 4mA. Am I reading this correctly? I also attached the s7-200 datasheet if you have time to varify that, please.
Thanks in advance for any help.
Regards,
Jinyu