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The image below is a LEGO specimen stage designed for a stereo microscope. I am looking for a recommendation for a PC controlled motors that allows for very small and precise movements.

I want use the motors attached to my specimen stage to make a very small height adjustment and then I want to send a command and capture an image from the camera-mounted to the microscope.

Here is the workflow I hope to achieve by motorizing the specimen stage:

  • On KeyPress (from with C# Windows application)
    • Activate stepper motor, adjust height (z-axis) by 100-200 µm (maybe 2-4 steps in a 200 step per revolution motor)
    • Wait 200 ms (allow time for vibrations from movement to stop)
    • Activate Camera - capture an image
    • Save image (auto-named) to my folder.

Possibly using SDK like: https://github.com/pololu/pololu-usb-sdk

Any Suggestions?

Lego specimen stage

Working solution: The picture with the stepper motor on the input: enter image description here Full View: enter image description here

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    What is "very small" ? How precise ? Did you account for the inherent slack in the system from the gearing (turning the first gear in a series of connected gears needs some movement before the last gear in the series starts moving) ? Does it need to be immediately reactive (is it allowed for the movement to take a while to occur and/or complete) ?
    – Sander De Dycker
    Commented May 13, 2022 at 15:04
  • 2
    Worm gears are usually slow, but quite accurate.
    – Alex
    Commented May 13, 2022 at 15:21
  • 2
    My first thought would be to hook a servo motor to an Arduino board, and use the Arduino's serial-over-usb capabilities to receive commands from a computer. However, the slack inherent in technic gears is gonna be an order of magnitude larger than the precision of any half-decent servo. If the goal is to raise/lower the platform repeatidly, two chained worm gears might be a better option.
    – IvanSanchez
    Commented May 13, 2022 at 17:07
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    LEGO gears were never designed to be precise so there always going to be some slack. But as I mentioned, you can achieve reasonable accuracy with worm gears. This would work if you want to make fine adjustment in single direction - while doing so you will have all gearing connected snugly, thus reducing any slack. But if you moved something to far and need to move it back a little then all gearing will come out of accurate setup until you reduce slack in opposite direction.
    – Alex
    Commented May 14, 2022 at 4:45
  • 2
    You could always build your own stepper motor from a regular lego motor, eg. one of sariel's designs.
    – Sander De Dycker
    Commented May 17, 2022 at 15:51

1 Answer 1

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Lego gear teeth have a pitch of 3.2mm (I did not measure. Maybe trust the www?)

You want .2mm or 200 µm.

3.2mm / .2mm = 16

Worm gears provide this with 360 degrees/16 = 13.5 degrees

I'd suggest 4 motors, each driving one set of worm gears on the four corners of the platform being raised/lowered. Of course, you may not have four motors. Adding a gear train will lower the accuracy. There are 40 tooth gears, that when combined with the 8 tooth gears could work. The worm gears are tricky, they need to be braced; their symmetry is not obvious.

Interesting problem.

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