|Testing conductive paint as resistive element for a slider potentiometer|
|Simple connection to Arduino analogue input|
I'd like Valli to be able to control an aspect of the acoustic system we offer her. I've considered a theramin-style device, but the conceptual mapping between proximity and output seems a bit vague and potentially hard to comprehend - after all, it's difficult for a human to master the controls.
Other possibilities might be a rotating knob or a lever that could be pulled. While I believe she could learn to use a knob, turning things is not an obvious aspect of an elephant's usual repertoire of movements (except twisting leaves off a branch, for example). Pulling (which is very natural behaviour) raises manufacturing challenges - how to create something sufficiently robust?
Humans use sliders to control acoustics in synthesiser hardware, and the mapping between wiper position and output seems intuitive to us, so I thought I'd try and design a massive version of a slider potentiometer.
Slider pots have a resistive element, which can be coiled resistance wire, carbon film, carbon-impregnated non-conductive material, foil etc. A wiper moves freely along the element, sending different resistances back to the microcontroller (Arduino analogue pin). I have found that Bare Conductive electric paint is easy to use and provides a great element that can be sized to suit.
The wiper part became an interesting problem, as it needed to be sufficiently large and robust to be manipulated by an elephant, while maintaining contact with the element. I investigated the potential for repurposing old drawer sliders, which have a lovely smooth mechanism, but the runners are plastic, so no contact is made with fixed section, and they are heavy. A metal castor (see photograph) seemed easier to develop into a controller and worked well with the painted strip.
|Giant slider from back|
This is the current state of the device, seen from both sides. Small brackets, bolted to the top of the castor, pass over a wooden frame and hold a rounded "handle" that can be used to slide the wheel across the resistive element (electric paint). Aesthetics not yet finished.
|Giant slider from front|