The Roll Your Own Zone - Sensory Devices

Some of the most interesting technical innovations in this field can be seen in the sensory devices used to gather information from the real world. The purpose of these devices is to measure the actions of a person, often a performer, and to make the data available to a device that can respond intelligently to what is happening.

In terms of commercially available devices, we have attempted to list the best known and most readily available sensors here. For an exhaustive list, see Axel Mulder's excellent Human Movement Tracking Technology paper and its addendum.

This page is divided into three sections:

Making Your Own Sensors

There are two reasons that you may need to create your own sensory devices. The first strike against commercial sensors is probably their expense. We are artists after all, and that means we're usually short on cash. The second reason is that off-the-shelf objects may not measure the specific actions that you are looking for, or may not measure them in the way that you need. This section is designed to help you find the information you need to create simple and relatively inexpensive interactive sensory systems.

If you are a beginner, we strongly encourage you to start at Dan O'Sullivan's incredible Physical Computing pages. This "hands on guide for artists" goes into great detail, from choosing sensors to soldering to interfacing them to a microcontroller.

Next, we would like to list a few very simple ideas for beating off-the-shelf components into submission for your own purposes.

Drum Controllers and Drum Machines

Many drum controllers (Roland Pad-80) and some drum machines (Alesis HR-16) have inputs for external triggers. These inputs can be connected to piezo sensors, which respond to vibration or impact. You can purchase these sensors at Radio Shack very inexpensively, and then hook these up to the inputs on the drum controller or drum machine. Once you have done so, striking the piezo should generate midi note on / off messages. Because they are small and thin, the sensors can be attached to a number of surfaces (walls and floors), embedded in costumes, etc.

MIDI Fader Boxes

There are a number of commercially available MIDI Fader Boxes, which usually sport a number of knobs or sliders. Moving the slider causes some kind of MIDI information (often a continuous controller message) to be sent out of the box. It is fairly easy to crack open these boxes, disconnect the existing faders and replace them with your own. This requires a bit of courage because it is possible to destroy the object in question if you are unskilled with a soldering iron, etc. The procedure is outlined below.

There are a number of possible applications, but obvious choices include measuring the angle of joints, how a viewer is touching parts of an installation, etc.

Note that we do not assume any responsibility for damage that occurs when modifying devices in the way described below. If you are at all unsure how to do the following procedure, either don't do it or find a knowledgeable friend to help you!

  1. Disconnect power from the device and open its enclosure.
  2. Look for the wires that are connected to the sliders or knobs (we'll call them faders from here on.) There should be three wires connected to each fader.
  3. Make a diagram of the wires connected to the fader. Better yet, number the contacts with a permanent marker and then, using a piece of tape, mark each wire with its matching number.
  4. Unsolder the wires from the fader.
  5. You will need to find out the resistance value of the fader. If there is a rating printed on the fader itself, i.e., 100K or 10K or something like that, you may not need to do the following procedure. If not, you can measure the resistance yourself using a volt-ohm-meter.
  6. To find out the fader's resistance value, measure the resistance between all three pairs of contacts. Two pairs will change resistance when you move the fader. One pair will not. The resistance of the fader between these two points is the fader's rated resistance. At this moment, the connection that you are not touching is called the "wiper." Make note of this.
  7. At your local electronics store or Radio Shack, purchase a potentiometer with the same rating as you found in the previous steps. Either a rotary or linear version is OK ­ whatever suits your purpose.
  8. You will want to solder your potentiometer in place of the fader that you disconnected. On the potentiometer that you purchase, you can determine the "wiper" in exactly the same way that you did above. On rotary potentiometers, the wiper is always the connection in the middle of the group of three.
  9. Attach the wire that used to go to the wiper on the device's fader to the wiper of your new potentiometer. Then attach the other two wires to the remaining two connection points ­ it does not matter which one.

That's it. You should be able to turn on power to your device, and use your new fader to generate MIDI in the same way in which the old fader did.

Custom Devices

Many artists have created their own sensory systems to suit their specific needs. These creations range from the simplest hybrids of multiple off-the-shelf items to systems that were created from the ground up. We have listed several of the devices that we know of here, in the hopes that they may serve as source of ideas and inspiration.

If there is an significant, non-commercially available system that we have omitted here, please let us know.

Commercial Devices (In Production)

Commercial Devices (No Longer In Production)

Because of the small number of creators making use of alternative controllers, many have come and gone. Still, you may find one of these items wandering about looking for a home so we felt it was important to mention some of these devices here.

Sensors | Interactive Languages | Presentation Devices | Roll Your Own | DT&Z

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