Electrics problem

[mireland]

I have just fitted - with advice from you all- a new Navman 5100 chartplotter and a Navman 7100 DSC VHF set. The NMEA output from the Chartplotter is connected to the 7100 and working well. So far so good. However my existing Tecnautics autopilot is now doing something very odd. When I hit the heading button it causes both the chartplotter and my ST3000 autohelm to reset. Its as if it interrupts the power momentarily. This did not happen priro to fitting the new instruments but for the life of me I cannot see what the problem may be. Your thoughts most appreciated. (My electrical knowledge is bettered by a pygmy hippo so please avoid jargon!)

 

[snowleopard]

i don't see a simple solution here but there are a few things to look at-

there should be no more than 2 or 3 items 'listening' to one NMEA output so you may have too much voltage loss on the nmea circuit as a result of adding extra instruments.

if the cable sizes to the instruments are a bit marginal the extra demand triggered by your action may cause voltage to drop enough to re-set some instruments.

there are various versions of nmea, for example i have a conflict between some requiring nmea 0183 v1.5 and others requiring v2.0 so check all the versiona are the same.

 

[toad]

Sounds like a voltage drop problem,have you taken the power supply for all the items from the same point?If so try wireing the Navman and autopilot temporary direct to the battery and see if that cures it.

 

[Koeketiene]

There are but so many things you can hook up. Try some research on your plotter; mine lists that no more than 3 other instruments should be hooked up to the one source.
An NMEA repeater could solve your problem (I think)

 

[mireland]

The first thing I did was to unhook the NMEA connection from the Chartplotter to the Autopilot to see if this cured the problem but it didn't. I think your voltge drop theory sounds good but the autopilot and chartplotter are not wired to the same point/breaker. I have taken the log, sounder and chartplotter from one point/breaker so this may be a problem though the log and sounder seem unaffected. My ST3000 backup autopilot also swithches off momentarily. This has its own take off point/breaker. All the instruments do of course come from the same distribution box. Is it possible that the additional instruments have simply caused too great a voltage drop along the supply cables to the distribution box itself? I thought this seemed unlikely but I begin to wonder. If so why is the problem only evident when I hit the hdg button on the main autopilot??

Questions, questions. Thanks for your advice.

 

[fireball]

Because when your turning on the main autopilot it takes a small surge before dropping back to a usual rate.
If you've isolated the NMEA issue then I would run a temporary cable directly from the battery to the autopilot and try that - that should indicate if it is a problem with your distribution box.

 

[mireland]

Cheers, I will try it tomorrow.

 

[bonny]

Looks as though it's a voltage drop problem, which as previously mentions will occur when the ap becomes active. Both the Navman & ST3000 will reset when voltage to them drops below about 10V. My ST4000 & 5600 plotter used to reset when I started the engine - not surprisingly. An old battery could also add to this problem. Does this still happen when the battery is being charged (shore power or engine alternator)?