Photographing Splashing Droplets

Up until now I’ve been using a photogate sensor and the Camera Axe to take pictures of water and milk droplets. After some research I found manypeopleonline were using solenoid valves to create droplets and take pictures of them. The big advantage to this method is it’s easy to collide drops which is was very difficult and random using my old method. I decided I’d make a new valve sensor (pre-built version available here) for the Camera Axe and document how to make your own since I didn’t find any detailed instructions or part lists on the web.

Building It

I knew I wanted to have a way to trigger my camera on a fairly long exposure in a dark room (I use a 1 second exposure). Then make a water droplet. Wait a little while. Make a second water droplet that would collide with the first droplet’s splash. And then wait a little more until the collision before triggering the flash. With this in mind I started making the different pieces I needed and connecting them together.

The only new circuit I needed was a simple motor driver circuit to drive the solenoid. Below is the one I designed and here are the PCB files I designed in Eagle.

Valve Sensor Circuit

Next I had to find and order the parts.

After assembly here is what it looks like:

I also made a new version of the Camera Axe software with the valve sensor. You can download this new version (3.0.03) from CameraAxe.com.

Using it with the Camera Axe

Plug your camera into Camera/Flash1. Plug your flash (or flashes using a splitter cable) into Camera/Flash2. Plug this new valve sensor into Sensor1. Below is a picture of my setup. It has two flashes, a camera, the Camera Axe, and the valve sensor.

Go to the valve sensor menu. Set drop1 size to a good starting size like 80. Set drop2 delay and drop2 size to 0 (we will start with only a single drop). Set Flash delay to around 200 ms. Then turn off the lights and press the “Set” button. This will trigger the camera and the flash. Now adjust the flash delay by 10 ms increments until you have a good droplet picture. Below is a video sequence of 20 images stepping through a milk drop splash. The images go from 220 to 420 ms.

If you want to do colliding drops timing is more complicated. As a starting point I’d suggest a drop1 size of 80, drop2 delay of 40, drop2 size 50, and a flash delay of 200 ms. Then adjust the flash delay until you find the time of collision. Then you can start adjusting other timing parameters to get all sorts of different types of pictures.

You can find lots of photos (including droplet pictures) on the Camera Axe flickr group. Below are a few of my favorites from yesterday.

10 Comments

  1. Alex Holsgrove said,

    April 5, 2010 @ 12:58 pm

    Those are some really great photos. Some of the shapes you have captured (on the flickr group) are pretty incredible. Thanks for sharing this.

  2. gary said,

    July 2, 2010 @ 6:18 am

    There are probably a thousand ways to control water droplets. The simplest, and most reliable I’ve found utilizes tubing intended to connect intravenous (medical) lines. The thumbwheel that controls the drip rate with precision, and the sharp end of the tubing fits nicely through a soda bottle cap.

  3. Blaise said,

    July 7, 2010 @ 5:30 pm

    I came across your very cool blog while looking up CNC designs.

    Your high speed photography reminded me of some research being done at MIT. I thought you might appreciate these photos.
    http://www-math.mit.edu/~bush/gallery.html
    Enjoy!

  4. h said,

    September 28, 2010 @ 4:51 pm

    Beautiful work. Behind every great artist is a great technician :)

  5. Colin said,

    August 7, 2011 @ 4:55 pm

    Do you have any tips on selecting a solenoid valve? I can’t get the one you used in the UK.

  6. Maurice Ribble said,

    August 7, 2011 @ 5:08 pm

    You can get that solenoid in the UK. There are also other options in the UK. Just do some searching on http://dreamingrobots.com/forums/viewforum.php?f=8 and you’ll get your answers.

  7. Ed said,

    March 10, 2012 @ 7:43 pm

    It would appear that my TIP102 xsistor is bad as I can’t get the unit to work (had worked previous).

    I short one side of the solenoid to ground and it trips so I know it’s good. I’ve ordered a new TIP102 to replace.

    I saw a note somewhere that said you were working on a new design….any word on it?

    Thanks for doing what you do!

  8. Felix said,

    April 14, 2012 @ 12:04 pm

    Hello,

    if i buy the valve sensor, is it coming with all the “cables” i need to connect it to the “Camera Axe” Module?

  9. Maurice Ribble said,

    April 14, 2012 @ 12:12 pm

    I suggest looking at this guide to help you understand what sensors and cables you need. http://www.cameraaxe.com/wiki/index.php?title=GettingStarted

  10. PaweĊ‚ said,

    May 1, 2012 @ 7:13 pm

    What is the max. frequency of this valve? Can i generate a chain of drops? for example few drops in the hight of 1m?

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