Reverse limit switch fail?

[mjhakkar]

hi fineabcyu,

I had a similar problem with PCI-7334 card. I was trying to use trigger input to capture alarm signal from stepper driver, so I had that HSC pin mode set to Drive Fault (Configure Drive Signal).  After I removed that and reseted card, limit switch started working normally.

[willamwang]

I am using a linear stage with 9512+7610 combo. The stage have two limit switches (as usual) and a linear encoder. I have an issue with one of the limit switches, which is on the negative direction of the encoder, so I call it reverse limit. The problem is very strange: the 9512 unit ignores the switch when the motor is enabled. This means, when I turn it with hands and hit the switch, the controller responses correctly; but when it drives the motor toward the switch, it go all the way to the hell until I disable the driver. As soon as the driver is disabled, it realizes the switch is on, and hold the motor. At the same time, the forward switch works as expected, stops the motor as soon as it is active. The engineer of the stage ensures me that both switches should act the same electronically, only the reverse switch is higher in mechanical precision. Both switches are connected to a common ground, so I used sourcing output setting for both on the 9512. 

[Buechsenschuetz]

I am not familiar with the 9512, but I checked the manual http://www.ni.com/pdf/manuals/374555e.pdf and found two schematics for connecting limit switches on p. 17 and p.18. If you are using limit switches with common ground, I think the "sinking configuration" might be correct. If you choose the "sourcing configuration", the 9512 (probably) expects a voltage level close to its internal supply voltage when the switch(es) are activated. This, of course, cannot be achieved when the switches connect their output to GND. 

Don't know why just one switch works correctly, but I would give it a try and connect the switches in "sinking configuration" (and initialize the driver accordingly,if necessary). Attention, it seems as if the headlines of Fig. 9 and Fig. 10 in the manual are swapped. Fig. 9 clearly shows a "PNP switch - output SOURCING device" while the headline says "configured for SINKING". The designators IN the schematics are correct, but the headlines obviously are not.