Main thesis site is here. Here is a point form summary of what I think about the affordances and limitations of different sensors in the context of using them to construct Digital Musical Instruments for an interactive system. I also include examples of DMIs that use each sensor type.
Affordances: Light sensors measure the amount of light in an environment. They behave like proximity sensors when the environment is bright and a hand waves in front of the sensor to block the light. They can be used in an instrument or installation. Limitations:Before starting each performance, they need to calibration for the particular environment’s light levels. Examples:
Affordances:Gestures include a person holding a coloured object to the sensor or a person holding the sensor to a coloured object. They can be added to a wearable electronic, such as a glove, or in an instrument. Limitations:With colour sensors, the coloured objects need to touch the sensor and they can only sense one colour at a time. Examples:
Affordances: The colour can be on an object that a person moves around, or it can be part of the performer’s costume. It can also track multiple colours simultaneously. It is useful for both an instrumentalist or a dancer. Limitations: With USB cameras, there needs to be some distance between the coloured objects and the camera, as well as good lighting. Examples: Andrea Wong, CHIMIRA https://andreahywong.wixsite.com/chimira/
IMUs (Inertial Measurement Units)
Affordances:IMUs include 9DOF sensors that combine an accelerometer, gyroscope, and magnetometer. They sense the orientation of an object in space. These sensors are also available as a combination of just an accelerometer and gyroscope with 6DOF, or as individual 3-axis sensors. They are found either as part of wearable electronics for the hands or feet, or in an instrument. They are useful for tracking dancer’s movements, or large gestures of instrumentalists. Limitations:Accelerometers in mobile phones are useful for an accessible, low cost instrument. Compared to using just the sensor, an entire phone is bulky to wear in an armband. Tilt switches sense when they are tilted at a 90-degree angle. They only report on and off. They can be added to wearables or objects just like IMUs, but they are very limited in the data they report because they do not measure the orientation in between states. Examples:
Affordances:In general, they can measure hands moving above the sensor or the proximity of the whole body standing in front of the sensor. They can be used in instruments or installations.
Hall effect sensors measures the proximity of magnets to the sensor and usually have a short range of distance. They could be useful to measure the proximity of a specific object while simultaneously ignoring other objects within the sensing field.
There are three types of IR sensors: proximity, the IR switch and the IR breakbeam. The IR switch can only recognize when an object enters its field of vision and it does not measure the distance of that object. IR breakbeam sensors consist of an IR emitter and an IR receiver facing each other. They report when an object obstructs the IR beam in between them. These limited IR sensors could be used to trigger presets with a wave of a hand.
Limitations: the width and depth of their sensing field. Examples:
The reacTable, a tabletop for musical installations and performances, uses it (Jordà et al., 2007, p. 142-145).
Affordances: Depending on the intended gesture tracked, EMG sensors can alternatively be used instead of flex sensors, IMUs, or motion tracking. For sensing small finger movements, flex sensors can be attached to a glove. Or EMG sensors attached to a person’s arm can sense smaller finger movements. Limitations: EMG sensors must be in contact with a person’s skin to measure their muscle movements. Examples:
There are many different kinds of touch sensors. Capacitive touch sensors report two states: on and off. They are common among DIY projects as a means to introduce people to electronics because they are easy to make from household items.
FSRs measure pressure and they come in many different shapes and sizes. Small FSRs can be added to wearables in the fingertips of gloves or inside shoes. FSRs are common for DMIs because they are flat and reliable.
If the weight being measured is particularly heavy, then loadcells are a good alternative.
SoftPots are a type of touch sensor that does measure the location of a finger press along a strip
A resistive touch screen comes in different sizes and is transparent so it can sit on top of a custom picture or LCD screen.
FSRs must remain flat, so if the tracked object is bending, then a flex sensor should alternatively be used.
Most flex sensors can only bend in one direction without sustaining damage
FSRs, bend, and capacitive touch sensors do not report the location of where they are touched, pressed, or bent.
Softpots don't sense pressure (thought pressure can affect them slightly)