Underwater Sonar (Analog)

This page details the setup of a low cost analog underwater sonar (aka “fish finder”) and a digitizer to convert the analog readings into NMEA 0183 which can be read by ardupilot. This setup allows measuring the depth of the water below a boat. The sensor described has a maximum claimed range of 300m and a relatively wide beam of 22deg.

These instructions were provided by OlavA at the bottom of this ardupilot.org blog post

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images courtesy of lowarnace.com and actisense.com

Note

Support for this sensor was added to Rover-3.4.

Connecting and Configuring

The image below shows the pin-out of an airmar analog transducer but the pintout is the same as for the Lowrance HST-WSBL

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The Lowrance HST-WSBL pins should be connectded to the pins on the right side of the DST-2 as shown below. Note that the Lowrance HST-WSBL does not have a speed sensor so only pins 1 and 4-7 should be connected

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The DST-2 requires a 10V to 28V power source meaning it can be powered from a 3S or 4S lipo battery.

Next pins on the left side of the DST-2 (serial and RS-232 output) should be connected to the flight controller’s telemetry/serial input. The easiest connection method is to connect the DST-2’s 5V serial output directly to the telemetry port of the flight controller’s Tx, Rx and a common ground. It is best to check the DST-2 docs before connecting but below shows how the telemetry pins from a Pixhawk (or other flight controller) should be connected to the pins on the left side of the DST-2

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Connect with a ground station to the flight controller and set the following parameters (these settings assume the sensor is connected to Telem2/Serial2)

Then the following range finder related parameters should be set:

Testing the sensor

Distances read by the sensor can be seen in the Mission Planner’s Flight Data screen’s Status tab. Look closely for “sonarrange”.

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