Timelapse Dolly

By Chris | January 8, 2012

I have been developing a dolly for shooting timelapses for a few months. My goal was a low cost and lightweight system that was portable enough to be backpacked with. While both the mechanical and electronic aspects are a work in progress, the rail is at the state of being usable in the field.

Shooting at Carkeek Park, Seattle

After some sketches, I made a mockup in SolidWorks of what the rail, belt pulleys, and motor mounts would look like. I decided to use a section of 80/20 rail, along with an 80/20 slider. A key design goal was to allow the entire length of the rail to be used.

A stepper motor is mounted on one end and a bearing block on the other. Pulleys on each hold a 5mm timing belt which is attached to the slider.

The rail during assembly:

Specs and Components

Electronics

Arduino Uno 8-bit microcontroller
DFRobot LCD Shield
Modified miniE UI
Pololu A4988 Stepper Driver

The electronics are powered by a 9-35v DC input. I use an ATX power supply for bench testing and usually use a 12v sealed lead-acid battery in the field.

An 8v regulated output provides power to a dummy battery to power the camera. This also powers the arduino. The regulated 5v from the arduino powers the stepper driver logic.

An 4N35 optocoupler electrically isolates the controller from the camera. This connects to the remote shutter port on the camera using a 3/32″ TRS connector.

Motor

Anaheim Automation 23L9104XCS-02

The motor is a 0.9° step angle, offering twice the resolution of a standard stepper. Using 1/16 microstepping, this gives 6400 steps/rev. The motor is also IP65 rated and should be usable in any conditions short of full immersion. This motor sells for over $100. I caught a deal from an industrial liquidator on eBay and got this excellent motor for $30.

Mechanical

15 Series 1.5″ x 3.0″ Lite Smooth T-Slot Aluminum Extrusion, Part # 1530
15 Series Double Flange Linear Bearing, Part #6824

After lots of research, I settled on 80/20 rail and slider. The rail is a bit heaver that I would have liked, but it is very durable and sturdy. The slider is excellent – better than anything I could have made myself. The bearing surface is UHMWPE, which is similar to teflon but less expensive and more durable. So far, it has been working very well. On a rail, you want some stiction so you can sleep (cut power to) the motor between steps without the slider slipping.

The mounts on each end attach to only the bottom of the rail, and were designed to allow the slider to traverse the entire length of the rail. The free end is two pieces of angle aluminum. A revision halfway through the build to move the bearing higher up resulted in me gluing the bearings in with JB-weld. Not ideal, but it seems to work fine. The motor end was going to be angle aluminum too, but I didn’t have a large enough piece of angle to position the NEMA 23 stepper, so I welded a steel mount together. It is definitely study enough. I guess I can use it as a club in case bears attack me.

The motor shaft and bearings hold timing pulleys. A 5mm HDT neoprene timing circles over the top of the rail and back through the center channel. A small piece of aluminum clamps both ends of the timing belt down to the slider. It is simple and strong, but hard to adjust tension.

Hardware from sdp-si.com

Test Shots

Previous electronics (using an EasyDriver)

Two short sample shots

Cold Weather Testing

In early Janurary, I went on an overnight trip to Talapus Lake with my friends Sarah and Zach. Here, I was able to put the rail through its first serious testing. I set the rail up to do a very slow movement with 25″ exposures. I wen’t to bed not knowing exactly what I would find when I woke up. The temperature was about 20 F, and half an inch of snow had collected on everything. To my suprise, the rail and camera were still happily clicking away 8 hours and 1300 shots later.

Unfortunately, the sky was clouded the entire night, making the timelapse incredibly boring:

Exposure info: Canon XSi, Sigma 10-20 f/4-5.6. 10mm, f/5.6, 25", ISO400

Notice the slight flicker in this timelapse. This is due to aperture variations. Normally I lock the aperture down manually once I set up the shot, but I neglected to do this here, and the camera stopped down for each exposure and opened it back up each time.

To lock the diaphragm on Canon EOS with an AF lens, hold down the DOF preview button while disengaging the lens lock and twisting the lens slightly counter-clockwise. You will lose aperture-reporting information in the EXIF, but the exposure will be very constant.

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Tagged as: dolly • photography • timelapse

Timelapse Dolly