Panoramix
Super Anarchist
I think that it is a good start as long as one or the other (not both) is used as the common ground.
Chart Plotters for Dummies?
- Thread starter Bull City
- Start date
I think that it is a good start as long as one or the other (not both) is used as the common ground.
mckenzie.keith
Aspiring Anarchist
The ideal thing is to use a shielded cable for the three phase wires. If both sides of the shield were connected to the star point, then it wouldn't be a star point anymore. So I agree with you about that. I don't think it is a matter of getting back to earth (or sea) ground. I think it is a matter of providing as low an impedance conductive return path for the rapid dV/dt phase wires as possible.
You can try disconnecting it at the drive side to see if it makes any difference. But probably ferrites first!
Panoramix
Super Anarchist
+1 on the shielded cable !
Anything that stop motor wires radiating (ferrites close to the controller + shielded cable ) plus anything that stops interference getting in the circuits (short cables, star pattern) is going to help.
Thinking about it, may be the issue is the shield of the transducer cable. Check that it is connected properly on the plotter side.
The fact that immersing it solved the issue makes the shield suspect. By doing so, you were effectively grounding it...
PS : Apologies, rereading my post above I realised that I wrote " ferrite beads on the motor wires" whereas I should have written "ferrite beads on the motor controller power supply wires". Brain fad... If you were to add some on the wires between the controller and the motor, that could possibly affect the motor or its efficiency.
Anything that stop motor wires radiating (ferrites close to the controller + shielded cable ) plus anything that stops interference getting in the circuits (short cables, star pattern) is going to help.
Thinking about it, may be the issue is the shield of the transducer cable. Check that it is connected properly on the plotter side.
The fact that immersing it solved the issue makes the shield suspect. By doing so, you were effectively grounding it...
PS : Apologies, rereading my post above I realised that I wrote " ferrite beads on the motor wires" whereas I should have written "ferrite beads on the motor controller power supply wires". Brain fad... If you were to add some on the wires between the controller and the motor, that could possibly affect the motor or its efficiency.
Bull City
A fine fellow
- Thread starter
- #65
@Panoramix I'm a dummy on things electrical, so you mean the cables from the battery to the controller, n'est-ce pas?
Panoramix
Super Anarchist
Exactement !
Install the ferrite beads as close as practical to the controller.
From your experiment of dipping the transducer into the water, the more I think about it, the more I suspect that the transducer wire or the transducer itself is not properly shielded and picking up EMI from the motor. If there is an easy way to ground its shield (assuming there is one!), it is worth a try. I think that if the plotter was affected by a badly filtered controller sending back into its power supply parasitic AC (what the ferrite beads are trying to solve), dipping the transducer in the water would not have solved the issue. If I am right on this, shielding the motor wires should help also.
It is not easy to solve without poking around, your best bet is somebody who knows about RF. I own an electric car and I know that it is electrically noisy so I think that your boat is likely to be noisy hence the need to shield cables which carry data.
J_Grove
Member
You and everyone else on the thread are convinced it's an electrical interference problem and I'm not going to argue it's not. I'm certainly no expert. But I will say that before I had my current set up on my F27 tri, I had the same 4" Echomap as you, and more importantly also used a transom mount transducer secured in my bilge in a small pool of mineral oil (a kluge, kind of like your glob of wax). Sometimes it worked fine, and just as often I got the dreaded flashing non-updating depth. Unlike you, I could never definitively correlate it to anything else, sailing or motoring, deep water or shallow, etc.
The problem wasn't fixed until I got the right tool for the job: an in-hull transducer, and properly installed it. It's the Airmar P79. It doesn't do imaging but I don't care about seeing fish - just wanted reliable depth. I made sure to test it on the old 4" EchoMap before I upgraded to my new 9" Echomap UHD, and indeed it did solve my flashing depth problems. My old F242 tri had a solid fiberglass hull and mounting an in-hull is really easy in that case. My F27 has a layer of balsa between two layers of glass, and I had to cut away the inner layer, remove basla, thicken the outer layer of glass, and mount the transducer against that. (Actually I didn't do anything - I could have done it myself but chose to pay someone else who was doing other work on my boat at the time).
Do you know if your hull is solid glass or has a core? Core will cause echo problems with in-hull transducers, and I would think even more so if you are trying to shoot through it with what is supposed to be a transom mount unit. Perhaps your testing demonstrates with 100% certainty that electrical interference is the problem, but I find it interesting that it worked fine when you hung the transducer over the side. There is a possibility (in again my total-non-expert opinion) that the stronger signal of a properly installed in-hull may not be nearly as corrupted by the electrical interference in your boat, and that with higher SNR the processor in the Echomap may be able to separate the depth signal from the noise.
I got the P79 (the Airmar unit made for Garmins) for $150. You might want to consider that possibility before further payments to a marine electrician and possibly pulling your hair out trying to make shields and ferrites etc work. It's a tougher call if more is involved with installation, like in my case - agree it would suck to do a more involved transducer install and still have the problem - but it was also the only way for me to get a consistent depth reading in my boat.
The problem wasn't fixed until I got the right tool for the job: an in-hull transducer, and properly installed it. It's the Airmar P79. It doesn't do imaging but I don't care about seeing fish - just wanted reliable depth. I made sure to test it on the old 4" EchoMap before I upgraded to my new 9" Echomap UHD, and indeed it did solve my flashing depth problems. My old F242 tri had a solid fiberglass hull and mounting an in-hull is really easy in that case. My F27 has a layer of balsa between two layers of glass, and I had to cut away the inner layer, remove basla, thicken the outer layer of glass, and mount the transducer against that. (Actually I didn't do anything - I could have done it myself but chose to pay someone else who was doing other work on my boat at the time).
Do you know if your hull is solid glass or has a core? Core will cause echo problems with in-hull transducers, and I would think even more so if you are trying to shoot through it with what is supposed to be a transom mount unit. Perhaps your testing demonstrates with 100% certainty that electrical interference is the problem, but I find it interesting that it worked fine when you hung the transducer over the side. There is a possibility (in again my total-non-expert opinion) that the stronger signal of a properly installed in-hull may not be nearly as corrupted by the electrical interference in your boat, and that with higher SNR the processor in the Echomap may be able to separate the depth signal from the noise.
I got the P79 (the Airmar unit made for Garmins) for $150. You might want to consider that possibility before further payments to a marine electrician and possibly pulling your hair out trying to make shields and ferrites etc work. It's a tougher call if more is involved with installation, like in my case - agree it would suck to do a more involved transducer install and still have the problem - but it was also the only way for me to get a consistent depth reading in my boat.
Bull City
A fine fellow
- Thread starter
- #69
@J_Grove Thanks for relating your experience. A few thoughts:
- I have suspected EMI because the unit works fine while I'm sailing; within seconds of powering the motor, it loses the signal.
- I think my boat has a solid fiberglass hull, based on this from a survey: "The hull showed solid fiberglass reinforced plastic (FRP) from a female mold utilizing woven roving and stranded mat."
- Why did it work under power when the transducer was dipped over the side? I've got no idea. Maybe it's because the transducer cable was led out of the cabin, and away from EMI. Damned if I know.
- I am open to the idea of getting a real, properly installed in-hull transducer. I may do that, but I'm going to fiddle with the ferrite beads first.
Bull City
A fine fellow
- Thread starter
- #70
@J_Grove , @mckenzie.keith , @Panoramix , I got some more info today:
1) I put ferrite beads on the power supply cables (Battery -> Pod Controller) - no luck. I added one to the transducer data cable, next to the device, and another on the same cable where it passes near the cables which supply power to the pod - no luck. It was a beautiful day, sunny 75º, NE wind about 8 knots, so I went sailing.
2) While sailing the depth readings were fine until I hit deeper water. Then I would loose the signal. This would happen when I got to water 40+ or 50+ feet. The signal would then be off for most of the time I was in the deeper water, about 90%+ of the time. I might get a brief reading. As I approached shallower water, say mid-30 feet, the signal would return. Boat speed didn't matter.
All of this, plus the dipping of the transducer, suggests to me and the electrician that the problem is not EMI, it's that the transom-mount transponder sitting in a glob of toilet seal wax is just not cutting it.
I'm going to talk to Garmin. In the meantime, I would welcome comments.
1) I put ferrite beads on the power supply cables (Battery -> Pod Controller) - no luck. I added one to the transducer data cable, next to the device, and another on the same cable where it passes near the cables which supply power to the pod - no luck. It was a beautiful day, sunny 75º, NE wind about 8 knots, so I went sailing.
2) While sailing the depth readings were fine until I hit deeper water. Then I would loose the signal. This would happen when I got to water 40+ or 50+ feet. The signal would then be off for most of the time I was in the deeper water, about 90%+ of the time. I might get a brief reading. As I approached shallower water, say mid-30 feet, the signal would return. Boat speed didn't matter.
All of this, plus the dipping of the transducer, suggests to me and the electrician that the problem is not EMI, it's that the transom-mount transponder sitting in a glob of toilet seal wax is just not cutting it.
I'm going to talk to Garmin. In the meantime, I would welcome comments.
El Borracho
Bar Keepers Friend
What is the acoustic refractive index of toilet wax? 😜Seems like the signal could be greatly attenuated from quartz to wax to laminate (to mussels) to water and back again.
Losing signal at 40 feet is def. too early.
There must be signal loss in the wax-fibreglass "interface" as El Borracho mentions.
Just out of curiosity, is the reading accurate at dephts where there is one?
Btw, worst thing about my sounder is that from 85m (250 ft?) It either says "out" or very ocasionally 1,2 m (4ft)... gave me several near heart attacks, and even now that I know I still get uneasy from time to time. Does really not help that I "touch down" at a reading of 1.0...
There must be signal loss in the wax-fibreglass "interface" as El Borracho mentions.
Just out of curiosity, is the reading accurate at dephts where there is one?
Btw, worst thing about my sounder is that from 85m (250 ft?) It either says "out" or very ocasionally 1,2 m (4ft)... gave me several near heart attacks, and even now that I know I still get uneasy from time to time. Does really not help that I "touch down" at a reading of 1.0...
Panoramix
Super Anarchist
If you earlier observation that starting the motor interfere with the readings still stand, it is probably a mix then... Signal is very weak and I imagine that when you switch on the motor the weak signal gets drowned by the EMI.
Not sure how easy it is but shielding the motor-controller cables would help with suppressing the motor interferences. If not too difficult I would be tempted to do it just too limit the risk of further issues.
Switching transducer will probably fix the issue...
Hi Bull City - I'm just curious if you tried that test that I suggested in your original thread yet.
S35
Bull City
A fine fellow
- Thread starter
- #77
@S35 You mean:
No, I have not, but I may do it before committing to another transducer.
If you can, create a ring with that wax that's an appropriate diameter for the transducer. Make sure that the walls of the ring are about 1-1.5 inches high. Once in place, fill it with water and then put the transducer in the center?
No, I have not, but I may do it before committing to another transducer.
mckenzie.keith
Aspiring Anarchist
Maybe there is something other than toilet wax that could be used? Epoxy? You could coat the transducer with mold release. Or maybe the toilet wax residue will serve as mold release.
I am totally spitballing here. No expertise in this area.
I am totally spitballing here. No expertise in this area.
mckenzie.keith
Aspiring Anarchist
Yes it seems like that should work acoustically. You could also set it in bilge water possibly.
Yep - That's the one.
The idea here is to eliminate (as much as possible) any air between the shell of the transducer and the inside of the hull, so that the projected signal is stronger/ cleaner.
If that works, then epoxy it in place.
BTW - The transducer that I mentioned in that thread was also a Garmin transom mount, and it worked well through a fairly thick hull (40'er).
S35
