Home Chapter 9 Solid-State Relays, Passive Infrared Sensors, and Software Loops

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Solid-State Relays, Passive Infrared Sensors, and Software Loops

The aim of art is to represent not the outward appearance of things, but their inward significance. ~Aristotle


Question: Are there methods to control AC voltages in relation to varying sensor inputs?

Controlling an array of LEDs creates many possibilities, but the greater excitement comes in knowing that you can sequence and control almost any AC or DC device with the Arduino, Miditron or BASIC Stamp or your microcontroller’s logic-level control, connected to a solid-state relay (SSR). Devices such as AC and DC motors, high-brightness lamps, neon sculptures and signs, refrigerators and virtually any high voltage device can now come under the delicate and precise electronic control possible with your microcontroller. You can even interface the Arduino to the web.

The SSR is interfaced to the microcontroller and programmed to function in either a repetitive fashion or a chaotic one. Both repetitive and chaotic programming modes can be activated by a variety of sensors, such as the infrared sensor in this lesson.


A solid-state-relay (SSR) is a device that allows you to use a small DC voltage to switch a much larger AC voltage.


The artist David Foster is interested in Firefly communication as well as carnivorous plants such as Venus Fly Traps that eat insects, so he has created an electromechanical hybrid that alludes to these living entities.


Photuris muscipula by David Foster 2003, Photo by Scott Shelton


This work engages a critical look at biological research and the implications of working with transgenics. Foster’s works are metaphorical and meticulous sculptural constructions composed of steel, glass, and control electronics.


Transgenics is the art/science of taking a gene from one animal or plant and splicing it into another plant or animal. The artists Joe Davis has been working in this field and creating wonderfully original work.


In this sculpture, Foster used passive infrared sensors (PIR) to sense the presence of the participant. As the viewer approaches the work the infrared sensor triggers a sequence of behaviors and the light under the glass dome flashes on and off rapidly and the stainless steel petals of this techno-electro-hybrid subtly open.


Passive infrared sensors (PIR) measure a quantity of infrared light and look for changes in that signal. They are best used on a stable platform. These are the kind of sensors that activate the AC lights on peoples’ porches when you pass by.


Foster programmed this work so that each time the sensor is triggered a new behavior comes forth from a repertoire of pre-programmed but seemingly random responses. He also used an SSR to switch the AC lights on and off rapidly, and a powerful 12-volt DC gear head motor to open and close the steel petals.

The artist Reva Stone has been working with interactive installations, robotics, and responsive 3D environments for 15 years. Her installations explore the technological augmentation of the human body.


Carnevale 3.0 by Reva Stone with technical assistance by Dave Sandeman.2000-2002


The work Carnevale. 3.0 is an autonomous robot that is a surrogate of the artist as a young girl.

This robot uses active infrared sensors, which are suitable for moving platforms. The sensor system detects people and then triggers an onboard microcomputer to capture images with a mini digital video camera mounted on a cut aluminum form. The video functions as a form of memory for the surrogate and the captured images are then combined with previously stored images, which are projected outward from the metal body through a small video projector. This process of automated video capture, mixing, and playback addresses the idea of memory and stored knowledge.


Active infrared sensors work well on moving platforms as well as stable platforms. They send out beams of infrared light that, when reflected by living or nonliving objects, trigger the sensor.


Additionally, Carnevale 3.0 carries images from each of its venues to the next, building a database of “lived experience” in which the captured video images become stored memories of past captured events. For Reva Stone, the work investigates the relationship between somatic ways of knowing through the body and the ways in which bodily experience is merging with new technologies.

In talking about this work, Reva Stone says, “As a mediator of experience, this fleshless entity has the ability to exhibit human behavior by generating responsive movements, processing information, and accessing memory. Recollection, physicality and sentience become mutable entities.”