Do we have any 'Stepper Motor Control' expertise who might be able to guide me.

[Seapy]

I want to motorise my PB4 bellows, not the bellows itself, but the lower slide.

I  have devised a method of a worm and gear, driven by either a solenoid and pawl, or better, a stepper motor, which could provide fine incremental movement of the PB4 unit relative to the subject.

The mechanics and engineering are relatively easy, the control of the motor, while I do understand the principles, in practical terms is way beyond me.

I understand I may need a small computer like a Raspberry Pi and to do a little programming, given the widespread use and plentiful supply of affordable motors I feel it's worth learning the tech.  I just need pointing in the right direction...

I would like to control the start point, the step length, the number of steps and have a timed delay before closing the shutter release circuit to allow any vibrations from the movement to decay after each step movement.  Also the ability to return the platform to zero under power.

There must be a ton of info about this but I can't seem to find anything helpful.

[Birna Rørslett]

Unfortunately not my field either. However, why not contact the nearest LUG (Linux User Group) in your area? Linux magazines are filled with info in the Raspberry Pi sector and some of this might have rubbed off?

[Jack Dahlgren]

The Arduino platform is an easier way to get into simple motor control like this. There are many kits available for it which perform the sort of control you want. Here is a good example
https://www.adafruit.com/product/1438?gclid=CjwKCAiAlvnfBRA1EiwAVOEgfGdV5_V5uvobLaI0GTX2zJ-3rejMcsAh7RmCPrj3g8qx6bAQSqI06xoCe2oQAvD_BwE

There are also many code examples.

I’d recommend it over raspberry pi if you are just needing a microcontroller - which is what this sort of project needs.

[Seapy]

Thank you Jack,  just the sort of guidance I need.

I thought of Raspberry Pi because CPC is just down the road and they were involved with it's development I believe. I mainly get my electronics bits from CPC.

I will explore your link with enthusiasm.

[Seapy]

I am merrily stripping CD/DVD drives and examining the stepper motors.

CPC-Farnell, my 'local' electronics supplier has the Arduino controllers and probably most everything else I need.

Am really warming to this project, it doesn't seem as daunting, now I know a little more about it.

One slight dilemma I have is whether to remove the lower carriage knob from it's shaft and with a gear directly to the shaft or to make the gear fit onto the knob.  The knob is secured by a tiny grub screw and a 2mm roll pin, the grub screw should be easy enough to remove but the roll pin might be tight.  Removing it without causing damage might be a challenge.  Need to make a small press pin to push it out.

[Hugh_3170]

Hi Robert, I have sent you a new PM re my contact who is willing to assist with this project.  Get back to me when you are ready. Cheers.

[Seapy]

Thanks Hugh, much appreciated, eMail sent.

Am gathering bits and pieces at the moment.  Next stage will be to check out the software.

I have some engineering design quandaries to discuss regarding specific design features related to using a stepper motor.  Some things may not work as I am expecting/hoping.

I would appreciate some guidance from experienced focus stackers as to the likely range of step distance in various situations.

Obviously the further away from the subject the sensor is the greater the depth of focus, therefore presumably the bigger the step distance can be.  Also the number of steps relates to the depth of the subject or scene is wanted in focus.  I guess the focal length and aperture of the lens are important considerations too.

[CardBoardBoxProcessor]

I though about doing this once. You'd need an arduino and stepper motor control board. Lots of Arduino tutorials for this sort of thing. Raspberry pi might be over the top.

[Seapy]

Update:

Am slowly gathering bits and pieces.  I have a motor and an arduino board which came as a kit with breadboard and related components which match my needs to learn the controls and programming.  There is some doubt that the motor I have might not be suitable, or powerful enough for this task but I intend to take it one stage at a time and learn as I go, nothing to stop me making the motor work on the bench, practice controlling it and making it do what I want it to.  If it isn't powerful enough I will get another, bigger one.  That said, I think the motor I have is the same (or very similar) as those fitted to the commercially available stacking slides I have seen.

Right now I am concentrating on obtaining a D800, the focus stacking will follow on from that.

I have found a worm and wheel set which I like but it has to come from Japan, so I am waiting until after Christmas before ordering it.

I have found an Excel spreadsheet which allows planned device parameters to be entered and it calculates the suitability of motor specifications to load demand needs.  Don't fully understand it yet but getting there.