On Sunday, July 7, 2019 at 2:16:22 PM UTC-4, Charles Steinkuehler wrote: > There's good info in the data sheet for that part: > http://www.ti.com/lit/gpn/thvd1451 > ...which is an RS-485 transceiver (RS-485 is the same electrically as > RS-422, but the driver can be switched off). > RS-485 is a "multi-drop" protocol, and supports multiple transceivers. > Typically, the end nodes will have termination resistors populated > and the devices in the middle on the cable will have the termination > disabled. See figure 32 (page 22) in the data sheet. > PCW said it's straight RS-422, not RS-485. That means you only have > two devices making each device an end point, so add termination to > both ends.
That's kind of unfortunate because you'd need a separate channel for each device. Now my head is spinning again because my encoders and stepgens are differential recievers/drivers so I could technically pretty much just repurpose one of each and get a couple of channels out of one set of connectors. I didn't put any impedance control or TVS on them but now I'm thinking if I make some accommodations I can just sacrifice encoders and stepgens for serial channels. The ESD protection is application dependent, but you might also want > a small value series resistor between the THVD1451 and the cable (see > Figure 38, page 27 along with the recommend parts list) and see the > layout recommendations on page 29. > ...but don't sweat the details too much. For a short range (a few > meters) point-to-point connection, the ESD and even the termination > resistors are not super important. I'd still add them (it's cheap > insurance!), but I don't expect you're designing for 1.5 km long > cables that need to withstand nearby lightning strikes. :) > That said, spindle motors can throw off enough ESD to cause problems > even with differential signals, which is why you want _something_. I just whipped the drawing up this morning, I was originally going to use a different chip and had a different drawing. Good to know it's on the right track though. tvs and esd are somewhat of a concern since while I didn't really intend it, I can pretty much replace the x86 PC and 7i76e on my mill with this. In that case I use an 8i20 for my spindle with a power supply that consists of some big caps, a couple of SSRs and a bridge rectifier. There's 240v AC going into that box 320v DC coming out. While I shielded all cables, a little protection on the data lines is probably a good idea. Not sure of the performance of the DE10 Nano itself just yet since I just load up an Axis config and fire up halshow for the time being. Unless I converted my mill I probably wouldn't have an actual machine to run on this any time soon. Every time I think I'm damn near done with it I come up with something else to complicate things lol. -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/machinekit/a2e4e252-eda6-41a6-9dfe-971499328d56%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
