This is a project that allows you to use QLab to control a water drip and synchronize 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. It uses equipment normally used for high-speed water drop photography,  which automates the release of drips, and fires a flash at the point the drip hits the surface to take the photo. In this application, instead of triggering a flash, it triggers a sound replayed through a speaker directly behind where the drop will land.

Here it is in action (on the bench):

The Equipment used in the demo video was purchased from High Speed Photography UK on eBay. The normal Kit looks like this


Because this project uses  QLab to control it you 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 sends Midi Note on and off to a MIDI Solutions relay controller. The inrush 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.

Dripper Workshop Drawing

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 drips per minute.

You can download an example workspace here

Chapter Author: Mic Pool

Chapter Graphic: Pixabay distributed  under a Creative Commons 0 License

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