So, I'm just learning arduino and even newer at linear actuators but I'm looking to attempt a project using both sometime soon. I was hoping I could get a little guidance here.
The project I'm looking to take on is a macro focusing rail. What I'd like to do is mount my camera/extension tubes/lens setup to a motorized rail that I could move to or from my subject in small increments. Since macro photography tends to have very shallow focal plane, too big of a move can skip right over a good focal point. This is why small, controlled increments would be needed.
Questions:
-Can a linear actuator (or a stepper motor/lead screw/rail setup) be used in small, controlled, repeatable increments?
-Would I be able to creep the camera forward by, say, a fraction of a mm? If so, would I need additional equipment than just the actuator and arduino, like sensors or limit switches or would I be able to control the position just by figuring out the math of the travel?
-What specs should I be looking for in such an actuator? My camera setup should be less than 6lbs. in total (body, extension tubes, and lens). And the travel should be 4-6 inches or so. I don't think I need too much travel.
I plan to do this project in phases. This would be the first phase. If/when successful, the second phase would be to add a second actuator to move the camera side-to-side in addition to forward-to-back. If both work, then the third phase would be to polish up the software side in terms of control and interface and to set it up to focus stack more easily. But for now, I'd rather focus on accomplishing the first phase before I get too ahead of myself.
A point in the right direction, some tips, suggestions, warnings... any guidance is appreciated.
-Can a linear actuator (or a stepper motor/lead screw/rail setup) be used in small, controlled, repeatable increments?
Yes, using a stepper motor and lead screw. An 8mmx2mm lead screw driven by a 200 step motor in single step mode moves the nut 0.01mm per motor step. Set the motor to 16X micro stepping and the resolution is 0.000625mm per step. Small enough?
You should have at least one switch (or equivalent) to set the home or zero position at the start. After that you keep track of position by counting the motor steps. In a well designed system the stepper does not miss steps so that keeps accurate position.
A Google search for "arduino camera slider" should give ideas for the hardware and software.
Thanks for a well thought out and presented first post.
I agree with what @groundFungus has said.
If you need forward and backward motion, you will need to look at backlash on the drive system as this will add an error on change of direction actions.
Thanks for a well thought out and presented first post.
I agree with what @groundFungus has said.
If you need forward and backward motion, you will need to look at backlash on the drive system as this will add an error on change of direction actions.
Tom...
The backlash can be measured and brought into the code compensating when a direction change occurs.
Scrap an old printer or harddrive and You likely get a rather precise piece of hardware.
For my PROXXON MF70 made CNC I monted a fine indicator and offset it. Then a piece of code stepped a varying number of steps backwards and forwards until the indicator showed a little movement. What cabe done in software can reduce the hardware. Software never worns out as hardware does.
