For the past few months I’ve been working on an arduboat project based around a 36" boogie board and a humminbird Helix 7 mega si sonar unit. The boat has now been through 3 propulsion iterations. Ardupilot and the boat function perfectly with them all. However the biggest problem has been interference with the sonar transducer.
This has been surprising to me as I expected that part of the build to be plug and play. And since humminbird even makes trolling motor mounts for the transducer I didn’t expect to have any issues.
The first build used escs mounted in the dry electronics box with long wire runs to brushless thrusters under the boat. This was giving me lots of visible noise patterns in the sonar returns.
The second iteration used different brushless thrusters that had built in escs. I figured this would reduce possible interference from the ac motor leads. However the interference remained. At one point during testing I removed the props from the motors and removed the motors from their mounts. I lifted the motors out if the water while they ran at low speed. All interference went away. As soon as I put them back in the water it returned.
Now with the idea that I needed to get the brushless motors out of the water, the third iteration was a more traditional rc boat setup with twin dry motors mounted above water with flex shafts to props below. When I tested this setup I still had interference. I tried disconnecting the prop shafts from the motors and ran them. All interference was gone. So it seems that even props in the water are interfering with my transducer. Again since they sell a trolling motor mount for this transducer I was very surprised by these results.
So I’m now at a decision point on what to do next. I really want to stick with water propulsion if possible. It’s more efficient. Quieter. And I think it will be less affected by any wind. However going to an air driven system with above water props would probably solve the interference. My only other idea is to get an actual brushed trolling motor lower end and try using that for the drive. Being that that is supposedly the propulsion system this sonar is designed to work around i would hope that worked.
If anyone has any experience with side scan sonar and interference like this please let me know your thoughts.