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DIY Auto Focus Rail - Part 2
Posted By: AggieDad, 08-17-2018, 05:55 PM

The "Build Your Own Automatic Macro Focus Rail" continues, albeit slowly. Here is the latest progress report.

I have completed the programming for the rail, including snapping the shutter and all is good. The sequence is as follows:
  1. Back up the camera and move forward to start point. This takes any slack out of the linear screw as its last move was a return.
  2. Move forward and wait to settle everything before taking picture.
  3. Fire the shutter and take the picture. Wait and settle.
  4. Move, wait, shutter, wait. Rinse and repeat as needed.
  5. After last photo move the carriage back to the start position.

The only entries required are the thickness of the stack slice – essentially the D.O.F. – and the number of slices wanted in the stack. The actual slice thickness will be 80% of the entry. This will create overlap for the slices.

My code is considerably more simplistic than that of others I have seen on the Internet. Most of these guys seem to get a bit excited and try to do everything. All I want to do is move a camera and take a photo and do it over and over. So, no tricks, no frills.

I have considered using acceleration/deceleration for the stepper motor, but, for the moment, have decided against it. With the small number of steps taken for each slice, the motor would never be at a fixed speed. It would always be accelerating or decelerating. My tests with a load (K-5iis and a big old 200mm metal lens) have shown good accuracy, so I am currently satisfied.

The project of the moment is coding the entry system. I am using a 4x4 keypad and a 2-line, 16-character display. This is about half-way complete, but the second half always seems to take three times as long. So, who knows? When the entry system is complete I will fold all the code together and complete the system.

Then all that will be left will be to put everything in a box and make it look pretty. Unfortunately, this will require soldering many little tiny connections which could mean the project goes on into 2019.

Here are a few photos of the current rig in its prototype form. Also, if you have 3 or 4 extra minutes (or are incredibly bored) here is a video of the macro rail in action. To make it easy to see the movement, the step length is set to 0.4mm, and to keep people from becoming too bored, the delays have been shortened. You can see the flash which indicates the shutter has fired.

K-5iis mounted on linear screw carriage with micrometer in place.

The motor controller (left), the Arduino micro controller (middle), & relay for shutter (right)

Micrometer at zero. Accuracy of the micrometer is 1/100th of a millimeter.

Last edited by AggieDad; 08-18-2018 at 04:33 AM.
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08-17-2018, 06:38 PM   #2
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This is wonderful.
I'm glad you're continuing to post so that we may see the progress.
08-17-2018, 07:08 PM   #3
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That is awesome! Looking forward to Part 3.
08-17-2018, 08:31 PM   #4
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Good job!

08-17-2018, 10:10 PM   #5
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Thanks! Very informative - may tempt me to try one meself... Looking forward to the next phase.
08-18-2018, 03:05 AM   #6

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Impressive Hope we will see the rig in action soon.

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