This year, the FIRST® LEGO® League competition theme was “Nature’s Fury: Prepare, Stay Safe, Rebuild.” Team 1110, the CyborGirlz of Regina Caeli Academy in Spring, Texas, was inspired to study flood conditions based on reports from recent flooding in Ningbo, China. By interviewing survivors, the team learned that many people perished from a phenomenon called “electric shock drowning.” Live power wires under the water create electric fields in the water. Gradients in these fields drive current through the victims, paralyzing their muscles. As little as 6 mA of current can freeze a person’s muscles. The victim cannot move and then drowns.
The CyborGirlz created a small robotic boat, called the Aquabot. The boat carried a LEGO NXT robot, two Vernier NXT Sensor Adapters, and two Vernier Current Probes with leads immersed in the water. Electric field gradients in the water drove currents through the Current Probes, which were read by the NXT controller. The controller then powered two fans to move the boat through the water toward the region of higher current.
The robot was programmed to stop at the point of maximum danger and sound an alarm. In field trials using a one dimensional water tank, the Aquabot found the source of the electric fields in the water.
This project gave students their initial engineering design experience of identifying a problem, researching the problem, brainstorming and investigating an idea, creating and testing a design, modifying the design, retesting, and finally seeing the system work in operation.
More information about electric shock drowning can be found at www.electricshockdrowning.org