I think the ones I have will work well, they are probably just overkill.
I found this detailed page on how to wire switches to GRBL: https://github.com/gnea/grbl/wiki/Wiring-Limit-Switches
@chrismakesstuff on that page they detail a $2.30 board they published the design for that substantially improves the noise resistance of the limit sensor pins if placed in front of the Arduino inputs. It seems like a really good thing to include inside the Longboard the average Joe CNC buyer doesn’t need to think about it, or at least somehow offer it as part of a limit sensor kit for the Longmill?
As I’ve gotten more in to this over the past few weeks it’s become increasing clear to me that to really unlock the repeatability and accuracy of the machine (of any CNC) it is critical that you avoid crashing it and causing (even micro) changes in alignment and coordinates. Moreover, if you are doing complex, multi-part cuts (including tiling or cutting on both sides) you really need that accuracy to be maintained.
Recognizing that cost/price is always a consideration as well, it would still be good to have a check box item to add to the cart to add these recommended components that are known compatible with the Longmill and make it easy for new purchasers. For the time I’ve spent frustratedly re-aligning things and re-zeroing to try and get back to normal in the middle of a job, as well as the stock I’ve chewed up while learning about this, I would have happily paid $100+ to have had it all up front. Had it been properly explained to me.
I sometimes think the tendency is to over focus on price when promoting products, especially ones with elements of open source, instead of valuing the whole equation of price vs. time and materials. Obviously it’s different for everyone, but you may be surprised how many people would part with another $100 if the risk/reward was clearly outlined. It’s nice to have options…
I’ve got my switch behaving just like I would expect here on my “bench” (currently a large plastic tote sitting on a moving dolly with additional work space provided by the leftover box from my shop vac. Even so, I was pleasantly surprised to see those switches I bought have status lights on the back so you can instantly see, even with just power connected, that they are triggering on approach of metal.
This gentleman provided a wonderful overview of the switches and various resistor values to use to create voltage division to provide appropriate voltage for your microcontroller.
@chrismakesstuff is it correct that the pins are normally 5V high when the limit sensors are connected and they should be pulled love to 0V when they are triggered? It appears to be the case but there isn’t any detail on that here: https://sienci.com/dmx-longmill/adding-limit-switches/
Suggest adding a bit on the different types of switches, maybe a link to that GRBL page and a few details about the specs of your ports for limit switches. The switches I have report requiring about 300ma of draw but I think I saw in a post from Andy that (at least one port, maybe the PWM port?) is only good for 300ma total. How many amps could you draw on the 5V line for the limit switches? I suspect powering them separately or from the 24V supply outside of the Arduino is a better idea? I should go look at my Longboard, but do you expost 24V +/- anywhere on the edge connector?