Having already built several projects requiring a 12Vdc sequencer, such as my Prototype lamp
and my Conduit sculpture
I realized that experimenting with new projects with similar lights would be easier with a common development platform . . .
As part of a larger project supported by an artist grant from the Ontario Arts Council, I was able to build a prototype light sequencer, based on a PIC 16F877 microprocessor and two custom solid-state-relay output boards:
The PIC model was chosen based on its native I/O capabilities (16 digital outputs and several digital and analog inputs), and the solid-state-relays were chosen based on their high current carrying capability and low on-resistance, resulting in a negligible voltage drop across the relay (I couldn’t find an ideal transistor with a consistently low voltage drop when switching different load types such as cold cathode tube ballasts vs. EL wire ballasts, and was thus dissatisfied with the amount of voltage I was losing just to the transistor when switched on).
The PIC controls the output relays to directly switch the power from an external power supply to the loads (lights, motors, etc.); the advantage of this arrangement is that the output voltage and total available power of the sequencer is governed by this power supply which can be easily substituted based on the voltage and current requirements of a particular project.
The modular design of the system — main processor board and separate relay boards — allows me to mount the sequencer on the back of fixtures
or house it in its own enclosure:
The control board also has screw terminals for attaching input modules, such as this prototype proximity sensor based on a Sharp IR sensor:
Having a modular, easy-to-connect framework for the controller, sensor modules, and lights allows me to quickly experiment with various interactive arrangements, and has lead to several site-specific, interactive lighting installations.
Below are a few sample videos of some temporary installations built with the system. These installations used several motion sensors to control the light colour based on the direction or location of people in the exhibition space, while controlling the speed of the sequence based on the number of people passing through the space; the installations’ behaviour were thereby a reflection of the human activity within the space.
Future plans for the sequencer include migrating from a PIC processor to an Arduino (simply by changing the processor board), making more input modules, and creating a wireless network between the input and output modules.
More info can be found here.
