Reed switch endstops. Anybody else using them?



  • I was going to post this on @bartolomeus 'delta experts' thread but thought it could stand on it's own, I do not see any real prior discussion here/generally about this.

    As I upgraded my Delta I wanted to get rid of the 45cent microswitches it used (although they were working just fine, and now do endstop duties very reliably in my CNC, nothing 'wrong' with them) .

    After some thought and inconclusive research I ended up fitting three of these:
    IMG_20191018_112751.jpg
    They are pre-wired encapsulated reed switches, the little neodymium bar magnet next to it triggers at approx 9mm range, reliably and repeatably. Together with the magnets they cost more than I'd paid for the 3 aliexpress hall-effect sensors I didnt fit. You can see how small they are!

    Fitting being the nicest part of this:

    IMG_20190910_165102.jpg
    Looking at this I'm reminded I could shave 10mm off those tpu bumpstops/mounts with minimal effort.

    I soldered extensions to the wires, and they run down the front of each 2020 axis rail under a clip-in slot cover. Utterly invisible (which is important to me) and I had no need to mess around with 3 wires and bulky/vulnerable mounts.

    Crucially; the limited research I did suggests that these have excellent repeatability, and my experience bears this out. Sunflower (my Delta) keeps calibration when the PSU is off between prints; and an informal 10 second power outage test(*) picked up the resumed layer almost perfectly despite re-homing. Config/wiring identical to a NO endstop, if doing this again I might try and find NC reedswitches if they exist.

    To put it bluntly: I'm very happy with this choice, but I'd love to hear thoughts and experience from people here.(**)

    (*) In 22 years at my place I've had 3 power outages, so this is not something I'm guarding against anyway. My informal test involved a bottle of port and bravado.
    (**) Maybe not so many opinions though.. I prefer thoughts.



  • Only concern is that magnets are temperature sensitive, if enough to affect your setup I do not know.

    But thinking about it for 2 seconds, at higher temperatures the magnet should be weaker and the first layer height should increase making it a safe failure; if however during winter your ambient temperature drops you may find the opposite to be true.

    Curious to hear how you get on with different temperatures.



  • Hi,

    It it makes you happy that is all that matters.

    As you observed, micro-switches work just fine, so a person's preference then depends on other things, such as esthetics.

    Frederick



  • @bearer said in Reed switch endstops. Anybody else using them?:

    Curious to hear how you get on with different temperatures.

    Interesting point, I've also got expansion in the 2020 columns to consider, never given that much attention. I guess the Delta grows fractionally as she heats, could be worth setting a dial gauge up above a column and seeing what happens. My printroom is dry, fan ventilated and stable in temperature.



  • For reference (since there is fluff on my photo, sorry) the unit is a ms-213-3-1-0500, shows up like a rash in searches.
    I just discovered this, from the manufacturers website. In particular:

    How to achieve highest switching accuracy

    • Magnetic field should be "spot focussed" towards the contact area of the Reed Switch. Providing single pole actuation, smallest possible switching difference is the result.
    • Lowest hysteresis of Reed Switch is recommended since difference in switching distance between ON and OFF is very small for this type
    • The less tolerances for the magnet and Reed Switch, the better

    I'm at a loss over the last line.. but the rest makes me think I need to redesign my carriage brackets with the magnets mounted vertically, I got the maximum range in this parallel configuration but seeing their argument about 1 pole vs both makes me think I should change the magnet orientation.

    @fcwilt said in Reed switch endstops. Anybody else using them?:

    As you observed, micro-switches work just fine, so a person's preference then depends on other things, such as esthetics.

    Very much agree, I can also see the attraction of something complex, the hall effect sensors have bi-colour leds on them, which is also cool (I quite like flashing lights on futuristic things, too much SciFi in my youth).



  • @EasyTarget said in Reed switch endstops. Anybody else using them?:

    @bearer said in Reed switch endstops. Anybody else using them?:

    Curious to hear how you get on with different temperatures.

    Interesting point, I've also got expansion in the 2020 columns to consider, never given that much attention. I guess the Delta grows fractionally as she heats, could be worth setting a dial gauge up above a column and seeing what happens. My printroom is dry, fan ventilated and stable in temperature.

    oh, just in case youre thinking of taking a heatgun to your printer to test; don't . magnets will permanently demagnetize if heated above their Curie temperature, which is usually somewhere between 80 to 150C.



  • @bearer said in Reed switch endstops. Anybody else using them?:

    oh, just in case youre thinking of taking a heatgun to your printer to test; don't

    I was thinking of positioning the dial gauge on a convenient shelf so it is touching the column top, and then putting my printbed to 70C and leaving it for half an hour to see how the needle shifts from the index. Eg seeing what happens in realistic scenarios, applying direct heat would be silly, and unrepresentative.

    Im not worried about Curie temperatures; in this case it is 400C, though field strength will decrease well before that of course.. It should be acceptable over the temperature range I can expect.


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