This is a project that allows you to use QLab to control a water drip and synchronise the sound effect of the drip hitting a surface perfectly. It allows you to control the size and frequency of the drip directly from within QLab. When I knew I needed to produce this effect for a play by Sandi Toksvig, I had a hunch that something must exist that already does something similar. Sure enough, I discovered something called ‘water droplet photography’ which automates the release of drips and fires a flash at the point the drip hits the surface to take the photo. That was pretty much what I wanted to do but instead of triggering a flash I wanted to trigger a sound replayed through a speaker directly behind where the drop landed.
Here it is in action in the R&D Lab:
I bought the kit I needed from High Speed Photography UK on eBay. The normal Kit looks like this
Because we are using QLab to control it we don’t need the control unit or the shutter release cable. The important bits are the Marriotte bottle which keeps the water pressure even on the valve regardless of how much water is in the bottle, and the solenoid valve which is similar to the ones used in coffee vending machines.
To operate the valve QLab sent Midi Note on and off to a MIDI Solutions relay controller. The in rush current of the solenoid is greater than the rating of the relays in the MIDI Solutions relay box so we use that to control a 2A solid state relay closer to the solenoid. This also has the advantage of dealing with any voltage drop between sound control and the stage.
Here’s a screen recording of the QLab end:
Q40 Starts Cue DH. This Group cue does the following:
Starts cue DRIP1 which sends a MIDI note on to the MIDI Solutions Relay Box to open the valve and 50ms later a MIDI note off to close it again. The delay on the MIDI note off determines the size of the drops.
Then, after a pre-wait starts cue DRIPH. This is a random group cue which will fire one of the audio cues contained in the group at random. The pre-wait of this cue is set to the time it takes the drip to fall from the tank to the surface, in the example workspace 700ms
Cue DH Loops by starting itself. When you loop a fire all group you need to put a pre-wait on the start of the group. This is to ensure all cues within the group have completed when the group is restarted. I have used 100ms This in combination with the 900ms pre-wait on the start cue which restarts the group means that the group repeats every 1 second giving 60 drip per minute.
You can download an example workspace here
Photo Credit: Pixabay distributed under a Creative Commons 0 License
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