DollyShield: TimeLapse Motion Control (and more)

Forum 2005-2010 (read only) General Exhibition
1

Hi everybody,

While I was working on finding the right combination of open-source hardware to create a stand-alone 2-axis motor driver, with user interface, I got frustrated with a lot of the options out there, and decided to design my own. (That is to say, there were plenty of capable components out there, but trying to solve each major problem through combinations of them resulted in a very high cost.)

We call the shield the "DollyShield," and combined with the firmware I've created, it's the "MX2 Dolly Engine," (the naming makes sense for the project =)

The design is based on the Arduino Motor Shield v3, and uses the same L293B driver chip and driver circuitry. It expands on the normal capabilities of the motor shield by providing all elements necessary for a stand-alone user interface, an integrated and isolated camera connection, easy access to the hardware serial pins through a stereo jack, and an additional stereo jack connecting to pins 2 and 3 of the Arduino to allow for the use of encoders or limit switches. Pins 2 and 3 are chosen for their association with hardware interrupts which increase the reliability of encoder or limit switch actions.

As far as I know, it's the only shield that has both dual DC motor drivers and complete user interface, I could be wrong though...

The board design is, of course, licensed under CC 3.0 Attribution Share-Alike, and I intend to make sure any designs I release through the OpenMoCo community meet the OSHW definitions.

I'm using these to run motorized camera dollies, but they could probably come in useful anywhere you need both a motor controller and a UI. Additionally, I'll be showing in the next couple of weeks how to replace the internals for a Meade DS telescope head with this shield+arduino to unlock better capabilities.

Here's a quick rundown of the features:

  • 2x DC Motor Speed/Direction PWM Drivers (Up to 1A)
  • 1x 1/8" TRS Plug for isolated camera connection (focus+shutter)
  • 1x Camera exposing LED
  • 2x 1/8" TRS Plug for auxiliary I/O (Hardware Serial, Digital 2+3)
    • Can be used for encoders, limit switches, serial communication other boards, etc.
  • 1x 16x2 LCD for display
  • 5x Momentary pushbuttons
  • 2x DC Barrel Jacks for Motor Hookup (2.5x5.5mm)
  • 9v-12v supply voltage
  • Compact: 3.85x2.7"
  • Low-cost

and the MX2 Dolly Engine Firmware Features:

  • Alter any setting on-the-fly

  • Easy start/stop mode

  • Manual motor control

  • All basic control from a single screen

  • Camera Control
    ** Intervalometer
    ** Focus Trigger
    ** Shutter Trigger
    ** Exposure Delay
    ** Focus+Shutter link (for Nikons)

  • Easy Motor Control (speed/direction)

  • Speed in percentage or inch-per-minute

  • Linear output video speed ramping

  • Continuous Motion

  • Slow Motion Modes
    ** Enables far slower speeds than PWM alone
    ** Pulse for continuous slow mode (target average speed)
    ** Shoot-move-shoot to move between exposures

  • Adjust LCD backlight from software

  • Turn off LCD entirely after inactivity

  • Completely configurable with five buttons

More info about the board, including schematics, BOM, etc. can be found here: Loading...

More info about the firmware can be found here: Loading...

Here's a video walk-through of the basic usage: Dynamic Perception MX2 Dolly Controller Tour (part 2) on Vimeo -- this video shows it as part of a low-cost motorized dolly setup for timelapse usage.

I got the chance to give a talk about this shield in The Studio at SIGGRAPH last week, and had a lot of interest from people who hadn't heard about the project, so I thought I'd share it with a broader audience than just the timelapse community.

I plan on making these boards generally available for sale come late September, and they will be priced around $50 for a kit, or $80 assembled.

I would appreciate any feedback you have on this shield, or anything else you'd like to talk about =)

!c

2

Awesome project. I got a question.

Would you get a better picture if the dolly stops moving before taking a picture? If no, then why not?

3

Very cool. Well done.

(But you did have me cursing at my computer screen for 10 mins before we get to see the thing move - might want to put that and a sample of the captured images up front in the first 30 seconds of the video)

4

Salvador- I think I can answer that one. First is that exposure times are so short that rate of motion involved isn't of consequence (in terms of a daylight or well illuminated situation).. and in the case of a telescope, since the earth itself is in continuous motion and you are trying to compensate for that during a timed long exposure. If you take a 30 second exposure of the sky at night, the stars are not points.. they become lines (because the camera is in motion relative to the star) Everything gets "smeared". However, if you have a motorized system compensating for the motion, you can keep the camera trained on a point for long enough to do extended exposures.. and ideally the compensation (like the earth's rotation) is a continuous smooth motion and not discrete "detents" every few degrees. This combined with Image Stacking can make for some awesome astrophotography.

That's my educated guess, anyway :slight_smile:

5

For still photography move-shoot-move will be okay.
But if you want to use that footage for video then a little motion blur is often your friend because the footage looks much more smoother.

Using move-shoot-move (depening on the subject...) might look too jerky.

best regards
Daniel

6

There are actually a number of cases where each method is applicable.

Continuous motion is tied to minimum possible speed (although this can be faked using speed averaging techniques), and therefore largely unusable for multi-day timelapses (say, one shot every hour for several days/weeks/months).

Additionally, there are a number of "artistic" effects that can be produced using either. For example, when shooting 30s exposures to eliminate moving objects, but still having static objects sharp, S-M-S excels. (Whether or not it seems "too sharp" is often a subject of debate, rather than land on one or the other side, it's a no-brainer to do both.)

Additionally, when working with really long lenses and macro work, any vibration, including that of a running motor can blow focus. For critical focus work with big heavy lenses, S-M-S can be quite useful.

A number of people use S-M-S for star work, as "tracking stars" also blows your foreground subjects - blurring and smearing them. It's ok for stars to trail slightly, as the mind understands them as moving objects in the sky, but if the tree in the foreground is a blur, it can kill a shot. "Tracking stars" works well when only stars are in the shot, with real foreground items that draw and focus attention, you want some flexibility in how you create it.

An extreme is to move during the shots more than between the shots. I describe the benefits and drawbacks of each method in a very short article here: Loading...

!c

7

drone,

From where do you acquire the other components in your video (i.e. the track, motor, etc.)?

I would be super-interested in picking up a number of your shields if I had the other equipment to accommodate them.

8

I watched the full video... and whilst it was interesting, I kinda failed to see the point of taking photo's in that way? Could you expand, as it's not really floating my boat right now.

9

@twoblue: some of the components can be had off-the-shelf from 8020, SDP-SI, and Grainger, whereas other parts are custom built by us. The DollyShield will be sold as part of a larger package to timelapse shooters via DynamicPerception.com come September. If you look at the first video in that series, Jay talks quite a bit about pricing (less than $800 for everything).

@Funky diver: I'm not sure I get your drift, are you saying you don't like timelapse video, and want me to encourage you to like it, or you're not familiar with timelapse video? I'm not equipped (nor terribly interested =) in performing the former, but there's a lot of info to help with the latter...

The whole purpose of taking pictures like this is to create videos (one frame at a time!) showing the passing of time, often to great artistic effect.

Of course, timelapse isn't the only thing that utilizes this same technology, but to open up the doors on photographic motion control would take a lot more chars than I have here =) Try http://timescapes.org - look around on the forum there, there are hundreds of people uploading their videos, maybe something will catch your fancy, or not.

!c

10

Cool... cheers for that :smiley: hit's the link