Question about grounds an interference.

[sutor623]

Hey guys having an issue with interference from my trolling motor to my bow mount fishfinder. I am going on a fishing trip next week and cant water test, so I installed some ferrite rings and grounded my trolling motor battery to my fuse buss ground. If I turn my trolling motor and fishfinder on while in the driveway, will it give me an accurate reading of what my interference will look like on the water, or will the water give the interference a ground path? I guess the real question is this, if I see interference while on the trailer, would I expect to see it just as badly while in the water?

 

[dingbat]

Re: Question about grounds an interference.

Why did you ground the TM to the buss? You want to isolate it from the sonar circuit

Where did you connect the shields from the sonar?

 

[jhebert]

Re: Question about grounds an interference.

I do not think that immersion of the boat into water will have much influence on electrical noise that is a common-mode noise in your DC power distribution. Direct electrical currents of 12-Volts do not flow very well in water, particularly in fresh water.

 

[sutor623]

Re: Question about grounds an interference.

Why did you ground the TM to the buss? You want to isolate it from the sonar circuit

Where did you connect the shields from the sonar?

Dingbat, my sonar battery is completely isolated from my cranking and trolling motor. I just tried to ground the tm battery to buss becasue some have had luck with it. breaking that circuit is as easy as removing a fuse. The ferrite is on the transducer cables, and I am sure that is where the noise is coming from.

 

[dingbat]

Re: Question about grounds an interference.

Dingbat, my sonar battery is completely isolated from my cranking and trolling motor. I just tried to ground the tm battery to buss becasue some have had luck with it. breaking that circuit is as easy as removing a fuse. The ferrite is on the transducer cables, and I am sure that is where the noise is coming from.

disconnect the transducer. If the noise goes away you've found the problem. If not, you have a grounding issue

 

[sutor623]

Re: Question about grounds an interference.

I removed the ducer cable and the EMI went away. Ferrite ring in ducer didn't stop it. Not sure what to do now.

 

[dingbat]

Re: Question about grounds an interference.

You don't by chance have the transducer attached to the TM? New installation?

 

[sutor623]

Re: Question about grounds an interference.

You don't by chance have the transducer attached to the TM? New installation?

Sure do brother. I have a transom mount ducer that is doing great. The TM ducer is the one picking up the TM noise. I have a bow and console unit and they are networked together. I can use either ducer with either unit, but I like the ducer on the TM for cast netting bait.

 

[dingbat]

Re: Question about grounds an interference.

Good luck with that one. No excuse for emitting that much noise.

Pi$$ poor electronic design and no integrity to make things right.

 

[UncleWillie]

Re: Question about grounds an interference.

Don't count it out until you try it in the water.
Pinging in the air means little. Even less if in a barrel.

You could be getting returns from the spinning propeller because of the mismatch of the transducer to the air.
The sonic beam will not form the same in air as in water.
But be sure that the transducer cannot see the prop in any event.

A transducer in the air may also give wild results because the energy of the ping has nowhere to go except back up the cable.

 

[gm280]

Re: Question about grounds an interference.

Don't count it out until you try it in the water.
Pinging in the air means little. Even less if in a barrel.

You could be getting returns from the spinning propeller because of the mismatch of the transducer to the air.
The sonic beam will not form the same in air as in water.
But be sure that the transducer cannot see the prop in any event.

A transducer in the air may also give wild results because the energy of the ping has nowhere to go except back up the cable.

I whole heartedly agree with your assessment there UncleWillie, and if there was some way he could locate the interference frequency(s), he could also install a good filter system for those frequencies to avoid their interferences as well. There IS always a way with electronics...

 

[Fed]

Re: Question about grounds an interference.

You could try & re-route the transducer cable away from the trolling motor cable as much as possible.

 

[sutor623]

Re: Question about grounds an interference.

Don't count it out until you try it in the water.
Pinging in the air means little. Even less if in a barrel.

You could be getting returns from the spinning propeller because of the mismatch of the transducer to the air.
The sonic beam will not form the same in air as in water.
But be sure that the transducer cannot see the prop in any event.

A transducer in the air may also give wild results because the energy of the ping has nowhere to go except back up the cable.

I whole heartedly agree with your assessment there UncleWillie, and if there was some way he could locate the interference frequency(s), he could also install a good filter system for those frequencies to avoid their interferences as well. There IS always a way with electronics...

You could try & re-route the transducer cable away from the trolling motor cable as much as possible.

Thanks for your support guys. I had some interference while in the water, and was trying to troubleshoot on land because it is easier. But I can understand how that would yield inaccurate results. Humminbird has really great CS, and sent me an upgraded power cord with filter free of charge. ($25.00 new) I hope this will clear the issue up for me and will report back after the install!!

 

[UncleWillie]

Re: Question about grounds an interference.

Well that changes a lot!

You problem would appear to be with the Trolling Motor and not the sonar.
Solve the issue by eliminating the source and not try to hide it with filters.

Move the transducer away from the motor. If the noise remains constant the feedback is through the wiring.
If it reduces with distance the noise is electromagnetic.

I haven't played with trolling motors, but will assume they are brushed DC Motors.
Worn out brushes or damaged filter capacitors in the motor allowing the brushes to spark would be the first place to look.
How old (Hours of use) is the Motor?

Let's see a picture of the installation! hoto:

 

[sutor623]

Re: Question about grounds an interference.

Trolling motor is only 1 season old.

 

[dingbat]

Re: Question about grounds an interference.

Well that changes a lot!

You problem would appear to be with the Trolling Motor and not the sonar.

I stand by my synopsis of the problem four post ago.

The pulse modulation is a known problem on a lot of trolling motor. Some got it right, some did a pi$$ poor design job.

 

[UncleWillie]

Re: Question about grounds an interference.

Trolling motor is only 1 season old...

Has this configuration ever worked?
Is this a new pairing? Or a new problem?

The motor is relatively new. What Make/Model?
The Sonar looks very new also. What Make/Model/Year?

 

[sutor623]

Re: Question about grounds an interference.

Minn Kota Terrova 12V. Sonar is Humminbird 798 with side imaging, 2 years old. It was on the console, but I moved it to the bow and got a bigger console unit. These electronics have put me right on a ton of fish, and have been great thus far. Willie, this is actually a rare issue with this combination. Humminbird and Minn Kota (Johnson Outdoors) stand behind their products greatly and have offered great assistance so far. About a year ago, they started offering their filtered power wire standard on their side imaging units. My unit did not come with one, so H-Bird sent me a brand new filtered power cable free of charge. All in all I am very pleased. Just trying to get this last bit figured out and I think I may have done it. Will know as soon as I get my filtered power wire installed.

 

[UncleWillie]

Re: Question about grounds an interference.

I don't troll, but I have The 798si also. Great for finding dive sites.
Let's see if the filtered power cord helps.

 

[sutor623]

Re: Question about grounds an interference.

Filtered power cord, along with the ferrite ring helped immensely. Hardly any interference at all now. Took her out for an entire week and it worked great!