Awkward Turtle
Sonar Subsystem

Awkward Turtle's SONAR system is broken down into two parts: the acoustic system and the signal processing system. The foundation of the acoustic system is 3 EDOŠ transducer hydrophones, which are mounted externally to the frame. These feed into a preamplifier circuit and then to a bandpass filter which limits the signal to 20-30kHz. From here the signal is sent to a high-gain amplifier and then into a comparator circuit that performs envelope detector based on a preset threshold. This analog circuit produces an edge pulsed that can be read by an external interrupt of the signal processing system.

A DSP PIC is the basis for the signal processing system. It marks the Time-of-Arrival (TOA) information from each hydrophone based on the triggering of each of its three external interrupts. In between pulses, the PIC uses trigonometry in order to calculate the bearing to target based on the TOA differential. The resulting target data is communicated to the main computer via a serial data stream.