Automating microscope focus

[elf]

Magnets are pretty weak in shear. If you get one that is strong enough in shear it will probably be dangerous to handle around ferrous metal.

[enricosavazzi]

I solved this problem by adding a precision rotary encoder to the motor controller. Turning the large knob of the encoder sends signals to the controller and rotates the fine focus axle accordingly. The advantage is that you can place the encoder anywhere it is ergonomically best. Another advantage is that the controller always remembers its current position, even when focusing manually, so it can always return to a previous position if necessary.

Again an excellent idea. With my skills it sounds like sci-fi for me, where to find and how to mount it? Would it play together with a controller like the Wemacro?

I have no knowledge of the Wemacro controller, but the rotary encoders I used are similar to this one:
https://cnhugong.en.alibaba.com/product ... _knob.html
This particular one has a resolution of 25,100 pulses/turn, which is far more than the necessary minimum. These encoders have just 4 contacts: 5V, GND, and two out-of-phase pulse outputs (which allow the controller to detect the direction of rotation of the knob). I found the Arduino code to interface to the encoder in the public domain and slightly modified it for my needs.

Anyone interested in the 2011 paper where I described my stacker and in its Arduino source code, PM me.

[JH]

Hi Pau

I use 4 small magnets:
http://www.photomacrography.net/forum/v ... 621#166621

The idea was that it should be easy to remove the motor and that they should "slip" if there was any problem with the focusing gear. I still use this solution and it works without any problems, but my fine focus moves so smooth that anything with some friction like two pieces of fabric/cloth would work as well.

The problem with my set up is that the height of the mount is not adjustable.

When I first had the opportunity to try stacking it was with a StackShot and Zerene. I very quickly got used to and really like the possibility to view the stacking process "live" in Zerene Stacker. It also means that I can follow the stacking to see if there are any problems – flower stamens sometimes move out of frame very quickly. So, for a person like me, not being skilled enough to build my own controller, I believe that the Zerne- StackShot combination is an appropriate choice even though it costs a lot.

Edit: To use the fine focus I have to disconect the motor cable.

I normally use “Hi Precision” but at least in my set up it comes with a high?pitch whine that I like to turn off after stacking. I do this by either disconnecting the motor or by setting a larger step size in Zerene - usually I just dial in 1 before my step size so if I use 0,0006 mm I use 10,0006. Maybe Rik could program Zerene so “Hi Precision” only starts when Zerene tells the motor to move?

Best regards
Jörgen Hellberg

[Pau]

I use 4 small magnets:
http://www.photomacrography.net/forum/v ... 621#166621

The idea was that it should be easy to remove the motor and that they should "slip" if there was any problem with the focusing gear. I still use this solution and it works without any problems, but my fine focus moves so smooth that anything with some friction like two pieces of fabric/cloth would work as well.

Thanks Jörgen,
These are good news for me!
My focus blocks are very smooth except the Olympus that I'd need to lube.
Could you post a detail picture of your coupling when opened?

[Pau]

I have no knowledge of the Wemacro controller, but the rotary encoders I used are similar to this one:
https://cnhugong.en.alibaba.com/product ... _knob.html
This particular one has a resolution of 25,100 pulses/turn, which is far more than the necessary minimum. These encoders have just 4 contacts: 5V, GND, and two out-of-phase pulse outputs (which allow the controller to detect the direction of rotation of the knob). I found the Arduino code to interface to the encoder in the public domain and slightly modified it for my needs.

Very interesting device...would be nice to have in the setup if on is able to install it

[Pau]

Magnets are pretty weak in shear. If you get one that is strong enough in shear it will probably be dangerous to handle around ferrous metal.

Thanks for the input.
Because flat neodimium magnets are inexpensive I could try with low risk, as they are strong perpendicular to the surface, some friction material sandwiched between it and the iron could serve to modulate the shear force, is it a good idea?

[Pau]

Have you looked at using CNC boards to control your motors?

Thanks perdu,
I know that skilled people can do wonders with this kind of devices...but I'm too old to learn a whole new field

[rjlittlefield]

Maybe Rik could program Zerene so “Hi Precision” only starts when Zerene tells the motor to move?

There is a wrinkle with this. Whenever the whine is turned off, the motor will move by itself to a new position that may be almost a half step different from where it is supposed to be. This would mean some inaccuracy in setting the stop/end positions. I have added the issue to my change request log, but nothing is likely to be done soon unless some super great solution occurs to me. At the moment, the best I can think of would be a button that specifically says "Stop the whine!" (or probably something less emphatic), that would turn the whine off only until the next move of any type.

--Rik

[Smokedaddy]

... ear plugs. <g>

[elf]

Magnets are pretty weak in shear. If you get one that is strong enough in shear it will probably be dangerous to handle around ferrous metal.

Thanks for the input.
Because flat neodimium magnets are inexpensive I could try with low risk, as they are strong perpendicular to the surface, some friction material sandwiched between it and the iron could serve to modulate the shear force, is it a good idea?

Anything between the magnet and its mate will weaken the force. It seems @JH's system works with four magnets, so that would be the first thing to try.

[JH]

Could you post a detail picture of your coupling when opened?

Hi Pau
I hope these pictures helps.
The magnets are much stronger than necessary.
Best regards
Jörgen Hellberg

[Pau]

Nice! this is the same I was planning but with a single wider magnet

[soldevilla]

Hello Pau. I am also a complete dummy in electronics. I show you the solution that I have adopted in my solar telescope. Sorry for the quality of the image, it is a cut of a complete telescope image made with my smartphone.
As I think you can guess, I use a DC motor of 12 V. It is very easy (although I do not know if very orthodox) to regulate its speed by varying the voltage of the transformer.

I have attached a machined part to the motor shaft to support a toothed pulley. A toothed belt goes from that toothed pulley to the focus knob, and the friction is enough for it to work perfectly. The clutch is a plastic disc that I fix with the wing nut (someday I'll change it with a knob). If I loosen that nut a bit, I can focus by hand using the knob on the other side. If I tighten it a little, the engine pulls it. And if it reaches the top, the plastic disc makes the pulley skid without causing any damage.

Finally, if someone is interested in producing a piece printed in 3D, I can contribute to the design. My job is to be 8 hours a day drawing 3D pieces

[Pau]

Nice design, Soldevilla

And if it reaches the top, the plastic disc makes the pulley skid without causing any damage.

This is the most interesting part for the discussion, although I can't see how is it implemented

[soldevilla]

Hello Pau.
I leave you the design images of my system. The friction washer is the one located between the knob and the pulley. If you want to have more security, you can add a spring between the knob and the washer, to be able to regulate the clutch pressure.
This pulley system I think can be adapted well to your need because the strap fits without problems to the different controls of the microscopes, you just have to control the distance between the axis of the motor axis and the knob of each microscope.