Fine focusing a microscope using StackShot

[rjlittlefield]

The one thing I'm having problems with is setting other parameters such as rail speed via the hardware controller. Reconnecting the USB seems to reset these parameters and the controller is locked out when the USB is connected.

Hhmm... Can you check again about that resetting behavior? What I've seen is that the parameters stick even across a power down, and the controller is locked out only when ZS is running. No problem with setting rail speed using the Config button when ZS is not running, and the setting holds for ZS. (Yes, rail speed will be exposed as a parameter inside ZS in a later version.)

In addition, I'm using live view on my Canon 5D mark II (via USB) in combination with the Stackshot shutter cable. Using these together stops the StackShot camera trigger from working the shutter on the camera. I'm therefore not sure how to fire the camera via the StackShot in live view.

I have no experience with the 5D Mark II. On my T1i, the required trick is to initially trigger Live View using the button on the camera back. Check also in EOS Utility for a setting that enables camera controls as well as computer controls. I don't think that one is mentioned in the documentation, but I have vague memories of running into it at some point.

--Rik

[Linden.g]

Your right Rik, I've just tested it. I cannot replicate the reset. I didn't realise that you need to shut down all of Zerene stacker not just the control window. I'll have to look deeper into the camera software to figure out the camera trigger during live view controlled by my computer. Thanks again for your help. I'll post a picture of the drive couple, I ended up using a drive belt.

[ckatosmith]

Will try this project today. On the Cognisys stepper motor shaft: do I need to remove the black plastic covering? or leave it on as it provides part of the 'grip' for the hole it would be inserted in (likely a dowel? ...off to Home Depot with my Nikon Eclipse E200 fine focus knob in hand).

Edited to add: Why is there a screw (the gold flat head) in the round wood piece that fits into the vinyl collar? and also the ?copper wire around the round piece of wood? I would have thought it enough to make sure the shaft is snug/secure in the hole of the round piece of wood.

Thank you.

[rjlittlefield]

Why is there a screw (the gold flat head) in the round wood piece that fits into the vinyl collar? and also the ?copper wire around the round piece of wood? I would have thought it enough to make sure the shaft is snug/secure in the hole of the round piece of wood.

The screw extends through the round wood piece to press on the motor shaft. Its job is to make sure that the shaft does not slip inside the hole. The copper wire is simply because small pieces of wood like this are inclined to split, so I wrapped it to prevent that possibility.

If you can get a sufficiently tight press fit, that will work fine.

do I need to remove the black plastic covering?

I am not familiar with that covering. My motor came with a bare shaft.

--Rik

[ckatosmith]

Thank you, Rik.

I was able to get it working. It is a forgiving setup. I don't have a drill press,
so my hand drilling for the shaft hole wasn't as parallel to the wooden cylinder sides as it should be, thus a slight wobble to the stepper motor
but it works. I will replace the wooden shaft holder when I can have it properly drilled. I did place two screws 180 degrees apart on the wooden cylinder, that really helped.

The Nikon Eclipse E200 spec states 0.2mm/rotation, so I assumed I could use the same 16 stp per STEP to get 1um movement.

[rjlittlefield]

The Nikon Eclipse E200 spec states 0.2mm/rotation, so I assumed I could use the same 16 stp per STEP to get 1um movement.

That sounds correct to me. And another beauty of this setup is that you can just watch tick marks on the fine focus dial to see if it's working as intended.

It is a forgiving setup.

"Forgiving" -- I like that a lot. Thanks for the feedback!

--Rik

[Chris S.]

Carolina,

I’d be a bit concerned about the "slight wobble to the stepper motor," for fear that this might be stressing the fine focus shaft on your microscope. The shaft on the stepper motor is much more robust than the fine focus shaft. You can see the wobble in the motor, but any bending of the fine focus shaft is probably hidden from view, under the fine focus knob.

The tubing in Rik’s approach likely flexes enough to absorb small alignment imperfections, but if your first try is misaligned enough to make the motor wobble, you may have exceeded this tolerance too much for comfort.

--Chris

[rjlittlefield]

The tubing in Rik’s approach likely flexes enough to absorb small alignment imperfections

I suppose it looks that way in the pictures, but that's not the way it actually works, at least on my unit.

On my unit what happens is that the tubing absorbs misalignment not by flexing, but rather by sliding longitudinally along the sides of the tapered surfaces so as to shift its orientation with respect to the shafts. It's almost like the tubing is acting as the center link in a double-joint universal system. No significant sideways pressure is applied to the fine focus knob, even with several mm misalignment between the two shafts.

This may be a case where the devil is in the details, or maybe not. On the one hand I avoid pressing the tubing very tightly onto either taper. On the other hand it seems that even if I do press them pretty tightly together, the vinyl quickly deforms so as to make the fit only snug after a short time. I suppose this is why most people recommend to clamp vinyl tubing onto fittings, rather than relying on its own elastic stretching. But for this application the light press fit is perfect.

--Rik

[ckatosmith]

Thanks Chris,

I have ordered a drill press...

[Chris S.]

. . .the tubing absorbs misalignment not by flexing, but rather by sliding longitudinally along the sides of the tapered surfaces so as to shift its orientation with respect to the shafts. . . . No significant sideways pressure is applied to the fine focus knob, even with several mm misalignment between the two shafts.

. . .I avoid pressing the tubing very tightly onto either taper. On the other hand it seems that even if I do press them pretty tightly together, the vinyl quickly deforms so as to make the fit only snug after a short time. I suppose this is why most people recommend to clamp vinyl tubing onto fittings, rather than relying on its own elastic stretching. But for this application the light press fit is perfect.

Rik, the additional details above greatly advance my understanding of how this system of yours works. I'd envisioned the flexure of the tubing to be what gives your approach the important advantages of a flexible shaft coupling; now, I see that a vital element is the taper of your wooden dowel and the fine focus knob. Quite different, this! So the vinyl tubing bridges two conical structures, and within a few turns, walks itself to a position in which any alignment issues are greatly reduced. Ah-hah!

I had noted that in your initial post, you said you had turned the wooden cylinder to make it slightly conical. But I saw this as an aid to placing the tubing on the wooden dowel, which it no-doubt is. l did not grasp the more important purpose of this conical shape--that it permits the tubing to self adjust to minimize alignment issues.

It might be well to more greatly emphasize that the dowel should be placed on a lathe and turned to introduce moderate taper. While you did this, it's possible that others besides me would not grasp the importance of this detail.

Carolina, enjoy your drill press! I'd like to have one, myself. And none of what Rik and I have discussed lessens my concern that your current wooden dowel might damage your microscope.

Cheers,

--Chris

[dolmadis]

Hi Chris.S and Rik

What is your view please of using a flexible coupler on the stepper shaft and running the PVC tube over that and the fine focus knob?

Here is an example of the type of flexible coupler I have in mind.

http://www.ebay.co.uk/itm/5-6-6-35-8mm- ... 0631482123

Thanks


John

[rjlittlefield]

It might be well to more greatly emphasize that the dowel should be placed on a lathe and turned to introduce moderate taper. While you did this, it's possible that others besides me would not grasp the importance of this detail.

One of the charms of having these discussions in public is that they automatically get recorded for consideration by others. I suspect that your suggestion can be implemented as a simple edit to the initial post, pointing to this later discussion. But I'll take a look at that tomorrow.

--Rik

[ckatosmith]

Carolina, enjoy your drill press! I'd like to have one, myself. And none of what Rik and I have discussed lessens my concern that your current wooden dowel might damage your microscope.

Cheers,

--Chris

Thanks Chris, I ordered a WEN 5-speed 8 inch for ~ $80 from Amazon (had lots of positive reviews). I believe it will be used for other things down the road also, so 'justified' it on that basis. But really, I like having the right tool for the job versus making do. Mostly, I couldn't ignore that I wanted to 'do no harm' to my microscope and that's what really tipped my decision, so thanks for pointing that potential out.

Edited to add: Oh no, do I now have to buy a lathe also ?

[rjlittlefield]

Oh no, do I now have to buy a lathe also ?

Nah, the drill press will work fine. Just whittle down the sides of the dowel with a knife and check your work by making it spin to see how badly it wobbles. As a side benefit, the whittling process will create longitudinal ridges on the wooden cone, which will improve its ability to provide torque even with quite loose fits.

What is your view please of using a flexible coupler on the stepper shaft and running the PVC tube over that and the fine focus knob?

Here is an example of the type of flexible coupler I have in mind.

http://www.ebay.co.uk/itm/5-6-6-35-8mm- ... 0631482123

Sorry, I can't say. I have no hands-on experience with those couplers, and my imagination permits several very different results. If you try it, I would be interested to hear what all happens.

It might be well to more greatly emphasize that the dowel should be placed on a lathe and turned to introduce moderate taper.

Done. I edited the initial post to emphasize the taper. The lathe is optional, as explained above.

--Rik

[Greenfields]

I have to confess that I was inspired by Rik's original post to have this clamp made for me by SRB-Griturn in the UK. The dimensions are made to slip almost over the fine control knob of an Olympus BHS stand and the screws grip it gently but securely. I can't say whether the control knob of another model would have the same dimensions.

I thought of asking the inside of the clamp to be tapered to fit the fine control knob instead of using the screws but was not confident that I could specify the taper correctly to achieve a push-fit.

The shaft was made 10mm in diameter because they asked me to make it larger than the original design of 5mm.

I found that the shaft of the stepper motor is marginally smaller than its nominal 5mm in diameter [4.97mm according to digital calipers] and fitted into the 5mm to 10mm coupling easily. Because the 10mm shaft was exactly 10.00mm in diameter it was a tight fit into the coupling. With that hindsight I would have asked for the shaft to be made 9.95mm.









The final picture shows the shaft of the clamp fitted with a 10mm to 5mm coupling.



Henry