Auto stop motors?

[Jayden]

9 minutes ago, gyenesvi said:

If I understand correctly, this would move the elevator to any position dictated by the slider, and the range (end position) could be set with the multiplier number (the other end being 0).

Correct. it actually works pretty well.

10 minutes ago, gyenesvi said:

One remaining question though is calibration, i.e. what is the zero position. I believe that will be the position the motor is in when the app starts, right? So if the elevator stopped in the middle, and the app is restarted, the middle becomes the zero position after restart, which is not ideal.. Is that any solution you know of for that problem?

Using the calibration block and then the slider+x blocks instead of the loop block would work 

[gyenesvi]

35 minutes ago, Jayden said:

Using the calibration block and then the slider+x blocks instead of the loop block would work 

Hmm, how would that work in practise? What would the calibration sequence do to arrive to the conclusion that the zero position is the bottom position of the elevator? Move the elevator up and down between the two extremes? Would that require the elevator to be built with a physical stop at the bottom/top? Would it also calibrate the other end, i.e. calculate the range as well? I guess if the elevator is held on a string then physical end stops would not be feasible.

[Jayden]

13 hours ago, gyenesvi said:

Hmm, how would that work in practise?

Pretty well actually, I made a garage which used a long gear rack to raise and lower the door with this code:

14 hours ago, gyenesvi said:

What would the calibration sequence do to arrive to the conclusion that the zero position is the bottom position of the elevator?

No the zero would be the middle but zero is also the middle of the slider.

14 hours ago, gyenesvi said:

Move the elevator up and down between the two extremes? Would that require the elevator to be built with a physical stop at the bottom/top? Would it also calibrate the other end, i.e. calculate the range as well?

Yes, yes, yes. 

14 hours ago, gyenesvi said:

I guess if the elevator is held on a string then physical end stops would not be feasible.

True. But if there is two winches and the elevator in the middle that would also work.  

[Hrafn]

Here is a purely mechanical proof of concept, which works no matter which way the motor is turning.  The motor is attached to the red liftarm (Bricksafe cropped the picture).

The motor remains on all the time, but when the output axle (with the lime connector and 20z gear) is blocked, the differential housing is blocked as well, and the orange gear selector disengages the red clutch plate from the gray clutch gear.  The dark gray 2L liftarm is blocked from rotating more than 90 degrees either way, and acts as a manual switch to re-engage the output axle when desired.

Construction notes:

The clutch plate is on a smooth 2L axle joiner, not a ridged one.  Obviously you would need a rigid structure- this just shows the positions of the parts.  And the orange gear selector tends to rotate slightly even when the output isn’t blocked, so it needs some friction or a rubber band or spring to resist that tendency.

Edited May 4, 2022 by Hrafn

[gyenesvi]

9 hours ago, Jayden said:

Pretty well actually, I made a garage which used a long gear rack to raise and lower the door with this code:

Thanks for all the exhaustive answers, great that you tested all these already! By any chance, have you tried programming it the way it works in the Liebherr's main controls, where if you move the slider out of the zero position it starts moving in that direction with speed proportional to the distance from the zero position, and stops automatically at the two ends? So that would be different from moving to the position dictated by the slider position. It would be cool if that could also be programmed!

9 hours ago, Jayden said:

But if there is two winches and the elevator in the middle that would also work.  

Sure, as long as the strings can withstand the force of the motors during calibration :)

8 hours ago, Hrafn said:

Here is a purely mechanical proof of concept

That's looks like a fairly compact mechanical solution, if I understand correctly it would work in both directions due to the symmetry of the orange catch, right? But what conditions are needed to actually make it work in a real application? Without a rubber band on the orange selector, it would probably engage and turn itself off under smaller load as well (i.e. the weight of the elevator). So if I understand correctly, you'd need a rubber band that is strong enough not to let it engage under the weight of the elevator, but not too strong to let it engage when the elevator is actually blocked, right?

[Jayden]

18 minutes ago, gyenesvi said:

By any chance, have you tried programming it the way it works in the Liebherr's main controls, where if you move the slider out of the zero position it starts moving in that direction with speed proportional to the distance from the zero position, and stops automatically at the two ends? So that would be different from moving to the position dictated by the slider position. It would be cool if that could also be programmed!

Indeed I have tried but it is very hard and I didn't succeed. All it did was slow the motor down.

18 minutes ago, gyenesvi said:

Sure, as long as the strings can withstand the force of the motors during calibration :)

True, I usually use a pretty durable "string" 

[Hrafn]

56 minutes ago, gyenesvi said:

That's looks like a fairly compact mechanical solution, if I understand correctly it would work in both directions due to the symmetry of the orange catch, right? But what conditions are needed to actually make it work in a real application? Without a rubber band on the orange selector, it would probably engage and turn itself off under smaller load as well (i.e. the weight of the elevator). So if I understand correctly, you'd need a rubber band that is strong enough not to let it engage under the weight of the elevator, but not too strong to let it engage when the elevator is actually blocked, right?

I think so.  A lot will depend on the motor, gearing, and load on the output axle.  You could use a return to center mechanism like the hockey spring, or, better, Sheepo’s return to center system (I would link to it but his site seems to having issues).

[Hrafn]

As usual I have over-complicated things.

Have a motor drive one side of a differential; have the output be the other side; add friction to the housing by meshing it with a gear on a friction pin.  When the output is blocked because the lift has reached the top or bottom, the housing will spin instead of the output.  
 

You can switch any of the elements around - the motor could dive the housing, or the housing could drive the output.

[gyenesvi]

2 hours ago, Hrafn said:

Have a motor drive one side of a differential; have the output be the other side; add friction to the housing by meshing it with a gear on a friction pin.  When the output is blocked because the lift has reached the top or bottom, the housing will spin instead of the output.  

Isn't that itself just a more complicated implementation of what a white 24T clutch gear goes? :) Though the clutch resistance may be different.

[Hrafn]

32 minutes ago, gyenesvi said:

Isn't that itself just a more complicated implementation of what a white 24T clutch gear goes? :) Though the clutch resistance may be different.

Fair enough! 😁