I made a little purchase in the middle of December, and there was a nice package waiting for me when I got home from holidays – Hall Effect endstops!
For those who aren’t familiar with the Hall Effect, it’s the voltage difference generated by a magnetic field. They can be used as a non-contact distance-measuring device. Hall effect sensors are used in various devices, most notably DC motors with fixed magnets, as a timing measure. The wiki page can be found here.
Its advantage is that it’s a non-contact, adjustable endstop. The problem that I have with the current endstops is that adjusting them is a pain. You have to have them attached fairly tightly to prevent them from moving during normal operation, but then trying to loosen them and adjust them by a small fraction of a mm is fiddly. This isn’t a problem for the X or Y-axes, which don’t require so much precision, but I find adjusting the Z-axis ‘just so’ to be very time-consuming and inaccurate. Lots of back-and-forth until the distance is ‘right enough’.
So, I purchased these Hall-effect endstops from mauk.cc. He makes these, and sells them fully assembled for 9 Euros each. At that price, I couldn’t resist giving them a go. I’m going to use this endstop to replace the Z-axis microswitch.
Due to limitations in the firmware, you can’t just set the printer to stop at a particular distance from the endstop. (Though that would be extremely nice.) It operates as a standard endstop, with an ‘on’ or ‘off’ signal. However, you can adjust (via a trimpot), the distance at which the ‘on’ signal activates. Thus, you can easily and quickly adjust the distance of the printbed to the nozzle.