One for the electronics experts!

[Iain C]

I've gradually added to the electronics and over the winter fitted a few new toys. I now have a Standard Horizon CP180 plotter, talking to a NASA cockpit GPS repeater, Raymarine ST1000 tiller pilot, XM DSC VHF, and a NASA AIS radar unit.

It all works fine when sailing, however when I start my diesel engine, within a minute the AIS radar is beeping away and saying that the GPS position has been lost, and it's using the last known position. This is despite the plotter being fine, and the other devices all still receiving the outputs fine. Only way to shut it up is to switch it off...not ideal.

Any ideas?

 

[macnorton]

I've gradually added to the electronics and over the winter fitted a few new toys. I now have a Standard Horizon CP180 plotter, talking to a NASA cockpit GPS repeater, Raymarine ST1000 tiller pilot, XM DSC VHF, and a NASA AIS radar unit.

It all works fine when sailing, however when I start my diesel engine, within a minute the AIS radar is beeping away and saying that the GPS position has been lost, and it's using the last known position. This is despite the plotter being fine, and the other devices all still receiving the outputs fine. Only way to shut it up is to switch it off...not ideal.

Any ideas?

It could be a voltage drop when the engine is started, can you power the kit from the domestic battery. might be worth a try?

 

[theoldsalt]

I agree with "macnorton".

The voltage drop when I start my engine causes the same effect.

When leaving my mooring I do not switch on my instruments until after starting the engine.

If sailing I have to reboot my instruments after starting the engine.

This is because I have a 1,2,both,off battery selector switch, so the instruments and engine starter motor all run from the battery selected.

I could avoid this by replacing the single selector switch with individual switches so that the instruments could run from a separate battery to the engine starter battery - but I haven't bothered.

 

[Iain C]

Hmmm, battery 2 is my domestic battery and will power the instruments when sailing. To start the engine, I will go to bat1, and then usually to both batteries once it's running to charge them. Still get the same problem though I think!

 

[theoldsalt]

Iain C,

Do you have a 1,2,both,off selector switch?

If you do then EVERYTHING runs off whichever battery you select.

Try starting the engine with 'both' selected. The extra capacity may reduce the voltage drop enough to prevent the instrument drop-out. However mine doesn't.

 

[johna]

Ian C

Install a small Red Flash dedicated engine start battery.

 

[savageseadog]

You need to make sure your starter and auxiliary equipment cables are separate, or as separate as possible. Have cables from the battery negative terminals to your distribution panel and a feed directly from your battery switch for the positive, use 35mm^2 cable for the starter and alternator. Clean the battery terminals and check for corrosion, check the battery voltage when cranking the engine, it shouldn't drop below about 9V. If your equipment is very sensitive to voltage drop it's possible to use a diode and capacitor to hold the voltage up for longer.

 

[LadyInBed]

Another possibility is noise from the alternator.
An electrical interference choke (capacitor) as used in car radio interference suppression might solve the problem, or feed the Nav kit via a LAPTOP CAR ADAPTER/CHARGER to get a stabilized supply.

 

[Amulet]

This used to happen to me all the time with a very much less sophisticated setup than yours. It involves a computer and a hand-held GPS which both should be able to keep going on their own batteries through a voltage drop. I concluded that it was electonic noise caused by the sudden huge current surge to the engine starter. I accepted it and just reset the computer to GPS communication if it failed. I have since replaced the home-made GPS to computer wiring with a continuous properly shielded cable. It almost never goes wrong now.

 

[bedouin]

If you switch the electronics on and off again do they start working okay (with the engine still running)?

What happens if you stop the engine - does it recover itself?

I tend more towards interference rather than voltage drop - you may want to look at the routing of the NMEA connection to the AIS to see if it passes near to the engine electrics somehow

 

[Beadle]

I've gradually added to the electronics and over the winter fitted a few new toys. I now have a Standard Horizon CP180 plotter, talking to a NASA cockpit GPS repeater, Raymarine ST1000 tiller pilot, XM DSC VHF, and a NASA AIS radar unit.

It all works fine when sailing, however when I start my diesel engine, within a minute the AIS radar is beeping away and saying that the GPS position has been lost, and it's using the last known position. This is despite the plotter being fine, and the other devices all still receiving the outputs fine. Only way to shut it up is to switch it off...not ideal.

Any ideas?

Perhaps worth switching all the electrickery off - then starting the engine - then switching electrickery back on.

If it still goes wobbly then it isn't due to volts drop on starting.

Other alternative is noise on the power supply - possibly/probably from alternator.

I believe it is possible to buy filters to keep alternator noise out of electronics, perhaps from a company supplying high end car radio/audio kit.

Perhaps worth checking wiring to electronics for iffy connections, joints - particularly on the earth side.