On Monday, December 25, 2017 at 6:34:25 AM UTC-8, Jeff Washburn wrote: > > My concept for a home, limit, and gantry squaring system is to use pogo > pins. The router would be grounded while the pins would be at 5V. A touch > from a pin turns that joint or axis off. That should be a highly repeatable > approach. > > The G540 has limited i/o and uses NC switches. My thought is to use the > 5i25 P2, but I don't think that I need the capability of one of the > daughter cards. Can I simply use a board to provide the wiring connections > from the P2 to ground and pins? I'm fairly sure that PNCconf and HAL will > allow me to work out the logic. > > On the other hand, the pogo pins could be used for homing and gantry > squaring, while serially wired NC switches could be used for limit and > crash protection. >
You can use FPGA pins directly for switches etc, with 5V tolerance enabled, they are safe with about -0.5 to +7V inputs and have pullups to +5V _BUT_ you have to be quite careful that they never touch frame ground as this almost always has significant HF noise coupled from step or servo motor drives and its easy to exceed the -0.5V limit with basically unlimited current. This will destroy the ground clamp diodes in the bus switches or the FPGA... This can mostly be prevented by adding a small series resistance to the inputs (say 100 Ohm) -- website: http://www.machinekit.io blog: http://blog.machinekit.io github: https://github.com/machinekit --- You received this message because you are subscribed to the Google Groups "Machinekit" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. Visit this group at https://groups.google.com/group/machinekit. For more options, visit https://groups.google.com/d/optout.
