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Notes
The project aimed to develop expertise in building interactive objects, which merged electronics, sensing and media technologies together.
For these notes the project has been divided into three stages:
- Development of the objects and the choice of the technologies to be used.
- The visit to STEIM, the development of the electronics and the isolation of the major technical problems.
- Further research into these technical problems, possible solutions and the manufacture of the printed circuit boards.
- Testing and finishing of the final prototype.
Details of these stages
1) Development of actual objects and the choice of the technologies to be used.
During the late stages of my PhD research I developed a methodology for working with interactive video installations. An important aspect of this was the significance of the spaces and spatial configuration of the sounds and imagery. In the context of this project this translated into a focus in the early stages on the physical objects and a desire for the behaviors and media to develop from the physical design. A number of possibilities were developed in different mediums. This included the exploration of casting shells and vacuum-form-moulding over shells. Instead of this, a balsa wood model was constructed that fitted comfortably into a userŐs hand and was suggestive of an abalone shell. The choice of size was also defined by the need to the make object large enough to house the speakers, batteries and the electronics. A flexible ultrasil silicone rubber model of this was made, and that object was then cast in semi-transparent polyester resin. This semi-transparency allowed for led lights to show through the object. The choice of techniques has meant the works can be editioned in small numbers.
When we find something on a beach we pick it up, roll it over, stroke it and hold it. These actions defined what the objects would sense. How these interactions were going to be sensed had not yet been defined.
After researching possible technologies, a decision to base the objects around the Basic Stamp version 2 was made for a number of reasons.
- Their ease of use, and the community of largely non-technical users that work with them.
- There exists a wide selection of modules and other technologies that work with Basic Stamps. This includes sound modules that store recorded sounds.
- Their relative low cost. Version 2 of the basic stamp has been on the market for a number of years, and has been superseded by the javelin stamp and at the same time its cost has decreased.
At this stage, accelerometers from Analog devices were chosen as the sensors to measure the rolling and tilt of the objects in the user's hand. Sound modules from Quadravox Inc were chosen as the solution to store and play the sounds.
2) The visit to STEIM, development of the electronics and the isolation of the major technical problems.
During this stage, and with assistance from the staff at STEIM, a number of technical problems were resolved. How the objects would engage with the viewers was also discussed. During discussions with staff at STEIM, the solution of using an infra-red phototransistor to sense the stroking action was identified as a possible solution. The circuit to sense both the tilting and stroking actions and the sound playback systems were prototyped on a breadboard while at STEIM.
The alternative music controllers that STEIM develops often need to allow a performer a wide and rich range of control; devices that a viewer interacts with directly need to allow for quick, simple engagement. What developed from this need for a quick and simple means of engaging the viewer was a focus on curiosity. This means that the objects are playful, and part of the user experience is exploring and discovering how the objects behave.
During this stage there was a change in focus on developing three separate objects to developing a series of objects that appear the same but behave differently. This also meant the objects could be based on the same technical platform.
A major technical problem was how to power the objects, this was a balance of having enough battery power to run them for a day, and maintaining the correct voltage levels and amperage load. The circuit board that was produced during this time was constructed on a prototype board. Space was at a premium when fitting all the electronics on the board and into the object. The solution to this issue was to design a professionally printed circuit board around which to build the object.
3) Further research into the technical problems, possible solutions and the manufacture of the printed circuit boards.
The possible solutions to these power supply problems were investigated back in Hobart. A solution to this was to use a 3v to 5v switching power supply circuit that could be shutdown and automatically turned on and off as the user engaged the object. There is not a commercially available, end user solution currently being manufactured. This meant that a new solution had to be developed. A circuit that uses a single chip and a minimum amount of additional components was developed, which included the use of the Basic Stamp as a battery-charging controller.
This power supply and the circuit developed at STEIM were then integrated into a computer based design of a printed circuit board. This was then sent to a printed circuit board maker for a short prototype run of six boards. Using these boards the assembly time of the second prototype was faster, and the final circuit board was neater, smaller and of a professional appearance.
4) Testing and finishing of the final prototype.
This new circuit board was integrated back into the object. There had been a number of problems with the design of the printed circuit board, mainly in the area of the power supply. This meant that at this stage the object was not battery powered and instead was being powered by an external power supply. This had some unforeseen positives as the external power cable added a degree of security in a gallery setting. At this stage I was able to explore which sounds worked well with the objects and which behaviors and scripts were interesting.