The Acadia University Physics Department decided to enter the fray in 2003, designing a SuperDuck to blow the competitors out of the water (not literally – the majority of faculty and students voted against arming the duck). The competitors were generally corporations, small businesses, or politicians from around the Annapolis Valley – out of 149 entrants, even one Physics Department was a bit of an ‘odd duck.’

The duck was named Sir Francis Drake. This name has both nautical and Physics connotations, as Sir Francis Drake was a British mariner who fought off the Spanish Armada (read Sir Henry Newbolt’s poem Drake’s Drum for further information), and the Drake equation is used in astronomy to estimate how much life might exist in our galaxy.

With a name decided on, construction could began. Propulsion seemed simple enough – just stick on some propellers. The propulsion system was made up of two simple hobby electric motors from a jetski toy purchased at a local RadioShack. Without a load, these motors will usually spin at 15 000 rpm. As for navigation, as remote control was not an option, other means of duck control had to be considered. The method we chose to use for control was sonar.

The sonar was provided by two piezoelectric transducers scavenged from old motion detectors. These were controlled by Polaroid 6500 rangefinder boards. This technology was developed for use in cameras as an early autofocus system. Today, the boards are commonly used in robots and other devices for measuring distances and rangefinding, and the specifications for their use are easily found on the Internet.

To operate the rangefinder boards, an initializing signal was first sent into one input of the board, while the two other inputs were connected to a voltage source and a ground, respectively. Since the voltage required to create a sonar pulse from the piezoelectric transducers is around 400 V, the 6500 rangefinding board requires a 5 V source capable of delivering 2 A. Its internal circuitry provides the necessary step up in voltage. As simple 1.5 V AA cells were being used in the duck, a 7805 voltage regulator was used to ensure proper voltage levels from the battery pack. Voltage regulators are not capable of delivering 2 A of current, and therefore, a reasonably large capacitor had to be connected from the ground of the regulator to the output. This capacitor stored enough charge to increase the current to as high as was needed.

The same transducers used to send out the sonar pulses were used to record the echo. The output of the rangefinder was a binary signal that switches to a high voltage when the sonar pulse was fired and to a low voltage after the echo was received; this repeated with each pulse. The initializing signal determined how quickly the sonar was fired. On the SuperDuck, it was run in the range of 20 to 50 Hz. This AC signal was produced using a 555 timer.

The closer a sensor came to an obstacle, the longer the signal would be low. The echo would return very quickly, sending the echo output to zero volts. The rangefinders were set on either side of the duck’s back with a slight forward angle to pick up when the duck was approaching a nearby bank. The outputs of the rangefinders were connected to the motors on the opposite side of the duck. In close proximity to the bank of the canal, the motor on the opposite side would slow down. This would pull the duck away from the canal wall. The 555 timer was outfitted with a potentiometer which altered the frequency of the initializing pulse. This had the effect of changing the rate at which the pulses were fired, which would in turn speed up the rate at which the echo signal was reset to high. In this way, the response time of the motors could be changed and optimized between trial runs. After weeks of preparation, it was finally race day.

The race took place at White Rock Canal in the Gaspereau Valley on 1 June 2003. The river course was approximately 500 m long and 20 m wide, with a 30-degree turn near the end. The water level sat a few metres from the top of the bank where spectators watched the race, while the opposite bank was a wooded area, ensuring that the ducks remained well away from human intervention – left to sink or swim on their own.

The Acadia SuperDuck did very well, winning second place and the Techno-Duck prize. The winning duck, Apple Blossom, was painted yellow and decorated with a ribbon, which happened to get caught in one of Sir Francis’ propellers. Thus, the two ducks orbited each other down the middle of the river to the finish line, with Apple Blossom crossing the line first.

The Department of Physics, which had sponsored the project, was happy with the results. A SuperDuck poster presented at the 2003 Canadian Association of Physicists (CAP) Congress now holds an honoured spot on a wall by a cabinet that will eventually contain a display of the duck. The display may be used to demonstrate what can really be done with Physics principles, thus attracting more students into the Physics program.

Meanwhile, the Physics Department prepares to return to the water once again and experiment with new control ideas. One possible idea is to make use of a compass to help the duck remain on course. This may be used in conjunction with a strategy used by a competitor, Nova Scotia Power, of streamlining the weight so that the duck is almost always pointed in the right direction. The compass would cut the engines if the duck did start to drift, ensuring that it remain pointed in the right direction. With these new strategies, the Department hopes to be able to claim the elusive first prize.

We would like to acknowledge the support of the faculty at Acadia University, specifically B. Latta, M. Robertson, C. Stanley, P. Williams, and the Dean of Science office.

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