Plain old inductive sensor for Z height?



  • I've been thinking about this a lot for my upcoming large corexy build (V-Core 2.0/400x400), and am really wondering what to use.

    As I'm really throwing some coin at the build plate and Z axis, I'm even considering just having one of these on one of the Z axis uprights, and not even having a probe on the hot end.

    https://www.aliexpress.com/item/32852113543.html?spm=a2g0s.9042311.0.0.15c54c4d3Mllxw

    I've got a bunch of them here, and I've see the Dentist pulls some very good repeatability tests, so I'm certainly open to it. If the bed measures up convincingly flat, it's even likely.

    But...in the event my bed isn't flat I'm not so sure. I've got the IR probe on my other machine, and while the startup homing is always perfect it doesn't do a good mesh map with my Printbite surface. I was looking at going with a genuine BLTouch, but the reviews are mixed at best on that one too.

    I'm really considering going to a good old fashioned inductive sensor, possibly the 12mm diameter body with the 4mm gap that seems popular.

    I've just seen that Toms review video on Z probes ( https://www.youtube.com/watch?v=il9bNWn66BY ) while and I don't mind paying for a good thing, these inductive probes seemed to be right up there for performance and down there for cost...no moving parts either.

    I'm using a Duet 2 wifi board. Will it run one of the 5v units directly, or should I go with the 6-36v . Will this board run a PINDA sensor correctly?

    This is actually not a cost saving measure, it's more about reliable utilitarian operation. Are all these new probes that are out there actually any better?



  • Hi,

    On my printers I use IR "beam break" devices for my end stop sensors.

    I install them on the Z axis as well and use that for Z homing.

    I am currently using BLTouch v3.0 devices for my Z probe and that is used for setting the Z=0 datum and creating the height map.

    Many folks use inductive sensors for their Z probe but try to find one that does not output a voltage when inactive and pulls the output to ground when active.

    I recently ordered one just to see if they can work on my printer. The silence would be preferred to the click-click of the BLTouch.

    Frederick



  • @Corexy said in Plain old inductive sensor for Z height?:

    Will it run one of the 5v units directly, or should I go with the 6-36v . Will this board run a PINDA sensor correctly?

    If you get a NPN* sensor supply voltage doesn't matter as much, active signal is 0v. But 5V might be simpler and safer, if you find one that works reliably at 5v, and doesn't suffer from decreased sensitivity at the lower voltage.

    I think people are using PINDA sensors with temperature correction, I've only skimmed the topics, but if you search the forum you'll find at least a good handfull of topics.

    *) with no built in pull up.



  • @Corexy said in Plain old inductive sensor for Z height?:

    he event my bed isn't flat I'm not so sure. I've got the IR probe on my other machine, and while the startup homing is always perfect it doesn't do a good mesh map with my Printbite surface. I was looking at going with a genuine BLTouch, but the reviews are mixed at best on that one too.
    I'm really considering going to a good old fashioned inductive sensor, possibly the 12mm diameter body with the 4mm gap that seems popular.
    I've just seen that Toms review video on Z probes ( https://www.youtube.com/watch?v=il9bNWn66BY ) while and I don't mind paying for a good thing, these inductive probes seemed to be right up there for performance and down there for cost...no moving parts either.
    I'm using a Duet 2 wifi board. Will it run one of the 5v units directly, or should I go with the 6-36v . Will this board run a PINDA sensor correctly?
    This is actually not a cost saving measure, it's more about reliable utilitarian operation. Are all these new probes that

    I played with a bunch of sensors, some $80 plus and came to the conclusion a inductive sensor with a flexible steel build plate was best, always get a perfect zero. Some sensors advertise 5v compatibility but it messes with their trigger distance and accuracy. Just run it 24 and setup a voltage divider. Oh and make sure you test the output voltage with a volt meter, better safe than sorry.



  • I use a NPN induction probe using a 24v relay module. The relay module makes it simple to connect.


  • Moderator

    I'd go with a genuine BLtouch. It's more complex setup, which trips up a lot of users, but in general it works and works well. If it seems like there is more problems with it than other sensors due to the amount of posts about it, also keep in mind that it is probably the most common probe as well.



  • I'd second the endorsement for BLTouch v3.1.

    I current have a PindaV2 which has served me well but it does have it's shortcomings. The Pinda is temp sensitive, where as the Pinda V2 included a therm to aid in offsetting the triggering distance due to temp changes - but this isn't always 100 percent correct - I guess nothing ever is though. Also depending on how your bed is configured can give you hurdles. Such as do you use magnets to hold your build plate on? These can throw off the Pinda sensor. Do you change the build plates and/or the surfaces? This will throw off the pinda and you will need to adjust for it - the height for each separate plate. Then there is repeatability - depending how you check this it can be called subjective.

    For all these reasons, and prob some others I can't think of at this time, I am changing over to BLTouch. Also - it is not difficult to do such, read the duet docs on it - i managed to test it in all of 5 minutes and I've only had the duet for about 30 days - don't fear setting it up. I have a pdf walkthough that addresses bltouch setup in the last few pages here: https://github.com/rkolbi/RRF-machine-config-files/blob/master/Prusa MK3s/Duet-MK3s.pdf



  • @Phaedrux said in Plain old inductive sensor for Z height?:

    I'd go with a genuine BLtouch. It's more complex setup, which trips up a lot of users, but in general it works and works well. If it seems like there is more problems with it than other sensors due to the amount of posts about it, also keep in mind that it is probably the most common probe as well.

    You are most likely right, it is certainly a very popular Z probe these days and does have a lot of support from the community. I would only use a genuine if I go that way.



  • @davidvh86 said in Plain old inductive sensor for Z height?:

    @Corexy said in Plain old inductive sensor for Z height?:

    he event my bed isn't flat I'm not so sure. I've got the IR probe on my other machine, and while the startup homing is always perfect it doesn't do a good mesh map with my Printbite surface. I was looking at going with a genuine BLTouch, but the reviews are mixed at best on that one too.
    I'm really considering going to a good old fashioned inductive sensor, possibly the 12mm diameter body with the 4mm gap that seems popular.
    I've just seen that Toms review video on Z probes ( https://www.youtube.com/watch?v=il9bNWn66BY ) while and I don't mind paying for a good thing, these inductive probes seemed to be right up there for performance and down there for cost...no moving parts either.
    I'm using a Duet 2 wifi board. Will it run one of the 5v units directly, or should I go with the 6-36v . Will this board run a PINDA sensor correctly?
    This is actually not a cost saving measure, it's more about reliable utilitarian operation. Are all these new probes that

    I played with a bunch of sensors, some $80 plus and came to the conclusion a inductive sensor with a flexible steel build plate was best, always get a perfect zero. Some sensors advertise 5v compatibility but it messes with their trigger distance and accuracy. Just run it 24 and setup a voltage divider. Oh and make sure you test the output voltage with a volt meter, better safe than sorry.

    Yes I'm going with a magnetic flex steel plate on a cast ally build plate, which is one of the reasons I'm asking about the inductive probe. The divider is no problem, and I'd run it at 24v myself.

    Do you have a link to the probe you used?



  • @fcwilt said in Plain old inductive sensor for Z height?:

    Hi,

    On my printers I use IR "beam break" devices for my end stop sensors.

    I install them on the Z axis as well and use that for Z homing.

    I am currently using BLTouch v3.0 devices for my Z probe and that is used for setting the Z=0 datum and creating the height map.

    Many folks use inductive sensors for their Z probe but try to find one that does not output a voltage when inactive and pulls the output to ground when active.

    I recently ordered one just to see if they can work on my printer. The silence would be preferred to the click-click of the BLTouch.

    Frederick

    Do you have a link to the one you ordered please?

    Thank you all for your advice.





  • @davidvh86 said in Plain old inductive sensor for Z height?:

    @Corexy

    https://www.amazon.com/gp/product/B07P5CH491/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

    out of stock but look for LJ18A3-8-Z/AX

    If you havent got a plate yet check out ezflex

    https://www.th3dstudio.com/product/ezflex2-flex-plate-smooth-or-textured-pei-coating/

    Thank you.

    So that's an 18mm diameter body on that one? Isn't that the one that triggers around 8mm from the bed?



  • @Corexy Do remember that when shifting build plate types - when using an inductive probe, the trigger distance can/will change. I've had good luck with the following in my config.g to rapidly setup.

    ; Z-Offsets - Read here: https://duet3d.dozuki.com/Wiki/Test_and_calibrate_the_Z_probe   
    ; G31 P1000 X23 Y5 Z1.240                        ; PEI Sheet (Prusa) Offset MICRO SWISS NOZZLE	
    ; G31 P1000 X23 Y5 Z0.85                         ; Textured Sheet (Prusa) Offset MICRO SWISS NOZZLE
    G31 P1000 X23 Y5 Z0.64                           ; Textured Sheet (thekkiinngg) Offset MICRO SWISS NOZZLE
    


  • given the trigger distance to what the sensor actually triggers against doesn't change, maybe using work offsets is a cleaner option than changing the probing?



  • @bearer Work offsets are prob the more correct option, but since it only took a few seconds to change and reset the printer with the above method, it was good enough for me at the time. But this is one of the reasons why I'm shifting to BLTouch...



  • @Kolbi said in Plain old inductive sensor for Z height?:

    @bearer Work offsets are prob the more correct option, but since it only took a few seconds to change and reset the printer with the above method, it was good enough for me at the time. But this is one of the reasons why I'm shifting to BLTouch...

    Hi,

    I don't setup my z probe in config.g.

    I have a separate macro for that that I invoke in code before setting the Z=0 datum using G30 or before creating the height map using G29.

    I also have a macro button that cycles the name of a dummy fan that I am using as a mode variable. When the probe config macro executes it checks the current name of the dummy fan and changes the probe settings accordingly.

    Now in my case I am changing from "consecutive readings" mode to "average readings" mode BUT it could be used in the same way to change any other setting, like the trigger height for different materials.

    I don't have to edit any code, just click the macro button to select the desired mode.

    Just a thought.

    Frederick



  • @fcwilt Nicely done, hence your prior research into variables - makes sense now.



  • @Kolbi said in Plain old inductive sensor for Z height?:

    @fcwilt Nicely done, hence your prior research into variables - makes sense now.

    While dummy fans are not ideal they allow, for now, what I wanted to do.

    My code is much simpler now in the sense I don't have to edit anything to change the settings, just click the macro button.

    I also have a "height map mode" dummy fan that controls the creation of the height map.

    Before I had 6 different macros that I had to edit in/out of code. Now I have two unchanging macros and the mode variables.


    Getting true variables is only part of the job. The dummy fan names displays in DWC like any other fan so I can see the modes at a glance.

    We are going to need something new in DWC to allow displaying of variables to use this approach with variables.

    Frederick



  • @fcwilt It didnt even occur to me the use/display of variables in DWC. That would be way cool, especially if you could assign the variable a title in DWC and display it's contents - just as anything else. Fingers crossed 🤞



  • @Corexy
    yes, the smaller bodies seem to have a closer trigger range, which might be a big deal but i wanted a good safety margin.


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