Sounder interference Problems

[Joe_Cole]

I've tried a replacement transducer and bought a new instrument but my NASA Target depth gauge is still having problems. Cutting a long (a very long!) story short I've now found the cause to be the solar panel which is installed directly above the outboard engine (just 2 or 3 inches). I can only assume that the solar cell, which has an aluminium backing is effectively acting as a darn great aerial and picking up either/or ignition/alternator interference which is then sent down the line to the sounder.

No other instruments are affected and I believe that the engine (2 stroke, twin cylinder) is in good order. The alternator produces all of 6 amps. I don't want to relocate the solar cell and I can get by by disconnecting it when the engine is running but I really need to fix the problem.

I think that I may need a combination of
1. Earthing the solar cell to the engine (a bit difficult, but it could be done)
2. Fitting a capacitator, but where and what size?
3. Possibly a choke but again where and what size?
4. Something else that I haven't thought of!

Any thoughts?

Joe Cole

 

[VMALLOWS]

This is really wierd! If you are certain that the cause is the solar panel, then yes,the first thing to try is some capacitors across the panel. As a first attempt, I would put something like 32 microfarad electrolytic (get the polarity right) in parrallel with 0.01 microfarad as near as possible to the panel itself.

Ignition interference from the engine seems more likely...... do you get the problem when the engine is off? Also, are you sure its not vibration causing air bubbles in the oil-bath of the transducer (assuming it has one).

 

[johmal]

I had the same problem with a NASA sounder - but for what it's worth I had no Solar Panel. The problem only manifested itself when the engine was running, and was less noticeable once the engine had run for a while. (less output from the engine).

I put the problem down to engine inteference and always meant to get round to fitting a car type interference supressor.

John M

 

[Joe_Cole]

Vic,

Thanks for the reply.

Yes, I'm sure that its the solar panel picking something up from the engine. Move it or disconnect it and the problem goes. For the same reason I'm happy with the oil bath....that's one of the many many things I tried before I identified the problem!

I'll try the capacitator as you suggest.

The pity with all this is that it simply confirms that there's not much point in my fitting a tiller pilot. It would have to be very close to the engine and if the solar panel picks things up I suppose that the pilot would. The other option would be to fit one with remote sensors but they're expensive and I haven't got the courage to ask SHMBO for the capital approval!

Regards

Joe Cole

 

[jfkal]

I had good results by using those snap on ferrites (as used in computer cable) on all cables to and from the instrument as well as one on the alternator output cable.

Good luck

 

[Joe_Cole]

Thanks. I'll try some.

I'm going to have so many electronic components soon that the boat will be low in the water!

Joe