DIY Motion Control Camera Slider

Introductory Video

This video is and introduction of my motion control slider project, showing the basics of what it can do and how it’s used.

Time Lapse Assembly Video

I figured that I’d record the entire assembly process of the MC slider from start to finish. This video shows about 24 hours of real time in 15 minutes, and in it I discuss some of the problems I faced and design choices I made.

Feedback

If you’ve got any comments or random abuse to hurl, please post it here on the ol’ blog.

Seriously, I’d appreciate any and all suggestions and I’m happy to answer any questions you might have. As promised in the videos, various downloads and a parts list are below.

Licensing

The YouTube videos are Creative Commons – Attribution licensed. You’re pretty much free to do whatever you want with the downloads below, however I ask that you provide proper attribution if you use them in your own project, and that you let me know about it. (Not because I’m some kind of jerk, but just because I’m really curious to see what you come up with!)

Downloads

Parts List

Most of these parts are from Amazon. I’m a sucker for 2-day shipping, and they have [almost] everything I need. The prices below are what I paid; Amazon’s prices can fluctuate widely and rapidly, and I didn’t necessarily look for the best deals on this stuff. You can probably put this together for less money, and if you price these parts out elsewhere, please let me know in the comments!

I also used some CAT 5e cable, six resistors, some miscellaneous nuts and bolts, and of course parts from my Makeblock Kit.

The Makeblock Kit

I bought the Ultimate Robot Kit back in September 2013. It was $288.99 at the time, and I’m kinda proud that I was order #311. (I ordered from them again in February 2015 and they’re up to number 23,705!)

The kit is expensive, yes, but the parts are of good quality and are extremely useful for projects like this one.

For the reason of the cost, I’m not going to say that you necessarily should use Makeblock parts. It’s just what I used. It’s hard to say what the beams, timing pulleys, motor bracket and etc. cost me for this project, but it’s probably about $50 if you were to pick them up individually.

Tools and Supplies

I had to buy a couple of extra tools and other miscellaneous for this project. You might have these already, and there are other ways to skin a cat. I posted this list in case you were curious as to what you saw me using and talking about in the time lapse video.

Video Transcript

This is the original shooting script for the Intro video. I figured I’d just throw it in here rather than re-typing all that same information.

Hi, I’m Scott and I made this video to show how I put together a… uh, where are you going?

{Camera moves back}

In this video I’m going to show you a motion control slider that I put together… This one right here, actually.

It’s based on one of the cheapest sliders available, and it has a stepper motor hanging off of it that’s connected to an Arduino. And that’s in this rather large controller along with the user interface components.

Besides just moving the sled back and forth manually, the controller can record and play back a series of movements and speed changes so it can do its thing without having someone to operate it.

So why a motion control slider? Mostly, I made it for fun. But the original impetus came from my HPRC/Pelican review. Towards the end of that video I had a sequence which showed gear being unloaded from the Pelican.

Check it out in full size. The transitions aren’t very smooth, and there’s tons of artifacts in that last one.

That’s because I don’t have the steadiest hands in the world. I did four or five camera passes, at four or five different speeds. It was one of the last shots of the video, and I got lazy: Rather than reshooting I just threw a warp stabilizer effect on it. That smoothed out the apparent speeds, but introduced all the artifacts.

So instead of using my own shitty hands, I figured I should just build a machine to do the same job.

Here’s a reshoot with the HPRC case being unloaded, using the motion control slider. Much smoother.

Besides shots like that, motion control is just the ticket for stop-motion animation, shooting in different settings for later composition, or just to act as camera operator when you’re a one-man show like me.

Here’s a slow motion shot of me dropping some RAM on the table. It was recorded at 60 frames per second, but you’re seeing it at 24 FPS.

Listen. This was my first real Arduino project, and I’m far from a mechanical or electrical engineer. I’m going to be telling you how I did this, but it’s not necessarily the right way to do it. If you go to s.co.tt/mc-slider you can download my plans, source code, and a materials list and make your own improvements. If you do, please let me know!

First, here’s a look at the slider itself. It’s pretty simple — those aluminum bars, the timing gears and the motor — all the mechanical stuff — are from a Makeblock kit. The switches came from Amazon, and it’s wired up using plain old CAT5.

My first mistake (and I made a few) was not planning where to mount the interface box, which is why it’s just sorta hanging there. But anyway, the box has a microstep driver attached to it, and all that’s inside are some wiring splices. It interfaces with the controller using an old-fashioned DB-25 male-to-male cable.

The controller is an oversized ABS plastic housing with power and slider connections, power switch, a potentiometer to control speed, a 4-row 20-column dot matrix LCD, and six buttons to control movement, recording and playback.

If you’re interested in details of the design and assembly, I made a narrated companion video which shows the entire process from start to finish. It’s time-lapse so you don’t have to be completely bored out of your mind as I screw around trying to figure out how to put everything together for hours on end.

Anyway, here’s how it works: The camera attaches to the carriage — or sled — whatever it’s called — as usual.

As soon as it’s turned on, the controller goes into calibration mode. At each end of the track are micro switches that are closed when the sled hits them. First it finds one end, then it travels to the other end and back again. The number of motor steps in each direction is counted, and if they differ by more than one percent the controller throws an error. This is to ensure that the whole thing is mechanically sound and that the sled isn’t binding up.

Once it’s calibrated, the sled should never hit either end switch. If it does, the motor will stop immediately.

At this point the stop button is lit and the display says “stopped”. Pressing reverse will of course start the slider moving in the “reverse” direction. When designing it, I first labeled everything “left” and “right”, but I realized that would be confusing if you were standing on the wrong side of the slider. Forward and reverse aren’t much better, I guess, and if I had to do it again I’d label everything right/left but implement a switch that programmatically changes left and right.

So as you just saw, the slider stops automatically when it gets close to the end. Of course you can stop it manually or change direction mid-motion.

The slider pot does pretty much what you’d expect. When it’s set all the way to the right it’s at maximum speed — all the way to the left and it’s at zero. It can be adjusted while the slider’s moving or before hand.

One difference is that if you adjust the speed when the slider is stopped it will update the display with the speed in inches per second. That allows you to match new moves with previous moves. Unfortunately calls to the LCD library are a bit heavy, and they create a noticeable jitter in the movement of the stepper motor. If I could do it all again I’d’ve used either a Raspberry Pi or two Arduinos: One to drive the interface and one to drive the motor.

The “lock” button next to the potentiometer will lock the speed setting so that it remains constant if the pot gets jostled.

I added the “bounce” feature in case I wanted to have the camera sweep the same subject repeatedly. In fact, it’s the way I reshot the case unpacking sequence. It’s also kinda cool. As you can probably guess from the name, it moves the camera between the two ends over and over again.

I guess the coolest parts of this project are the “record” and “play” buttons. When record is pressed and lit up, any change to the camera’s movement will be saved in memory along with a time stamp. Basically it records when forward, stop, or reverse are pressed, and records any changes in the value coming from the speed potentiometer. Since it’s based on time to millisecond precision, you can have camera moves match tightly to a planned sequence.

The record button toggles recording on and off, but hitting play will also stop recording and go directly to playback mode.

Once you have a sequence of movements recorded, pressing play first moves the slider to the same position it was in when the recording started. It then begins the set of movements.

Playback can be interrupted at any time by pressing the stop button.

The decal on the case may not be the best looking in the world, but it beats my original idea of just using a label maker. I designed it in Photoshop and printed it from my inkjet onto a full-page translucent Avery label. If you go this route, I’d recommend getting a white vinyl label — I thought it would be cool to have the grey of the case show through like where it says “s.co.tt” — perfect color match and all — but really it made the rest of the printed sections appear that much duller.

Another couple of things I would’ve done differently in hindsight:

I’d have put the power input on the interface box rather than the controller. After all, the slider is going to stay in place during a shot, but I might want to move the controller around when setting up.

I would’ve also used a lighter, more flexible cable than this 25-conductor behemoth.

I was kinda in a hurry to get this project started, and the project box for the controller was the closest one I could find to the size I needed, but obviously it’s bulkier than it needs to be. If you’re building one, hold out for a better box.

I also screwed up the size of the interface box: Originally I bought a stepper motor driver that would fit in there, but it was completely the wrong type. That’s why the microstep driver is piggybacked on to the outside. The connections from the motor and the micro switches to the interface box could also benefit from removable connectors: RJ-11s or RJ-45s would work great. Not using them was just sheer laziness on my part.

I couldn’t find a reasonably priced timing belt that was long enough and that shipped from the US. So I just stapled a couple together. It’s not as bad as it sounds — the staples have actually been holding up pretty well.

The stepper motor can be pretty loud, depending upon the speed. I had it wrapped in foam when I was shooting the opening of this video, but that’s not a good solution if you’re using it a lot — the motor will overheat pretty quickly.

And again, I should have implemented this with two Arduinos or a Pi. In order to have the motor actuate smoothly, I had to set the microstep driver to 3200 pulses per rotation, which is 16 times the motor’s spec of 200 steps per rotation. Asking the Arduino to process user IO as well as accelerate, move, and decelerate without jitter is a challenge. I had to make some compromises, like only updating the LCD when it’s stopped, and reducing the resolution of the speed control and button poll intervals.

Despite all that stuff I’d do differently, I still think this project came out pretty well. There are things I’m happy with, like the layout of the controls, the simplicity of the external cabling, and of course it’s overall functionality; It does what I wanted it to do from the start without too many compromises.

If you want to make your own version of my Motion Control Slider, you can find everything at s.co.tt/mc-slider like circuit diagrams for the controller and interface box, a parts list, the controller decal template, and the full assembly video.

Thanks for watching, I hope this gave you some good ideas to create your own motion control camera slider.