Raymarine forum

Full Version: [DG] S3G as backup of SPX-SOL
You're currently viewing a stripped down version of our content. View the full version with proper formatting.
Hi all

after reading the thread "SPX-5 as backup to EV-200" 11-01-2017, I would like to use my old S3G as a standby backup of the SPX-SOL.

As I have only ST1 network, I'll use a diverter applied to "off switch" contacts of both autopilots to have only one at a time working.

I think it's possible connect the solenoid and clutch cables to the respective contacts of both autopilots, but I don't know if it's possible to have the rudder and fluxgate sensors cables permanently connected to the respective contacts of both autopilots.

So before risking damage, I look forward to knowing the opinion of the guru.

All the best
It is essential to ensure only one 'pilot can be operated at the same time and so a 3 position switch should be used to isolate them, the centre position being OFF for both systems to ensure there is no possibility of them both being activated at the same time.

The compass and rudder sensors will also need to be isolated as they cannot be 'commoned' between the two systems. We also recommend isolating the solenoids and clutch too because you do not want to back feed power into the back end of the outputs.

Clearly the screen/shield can be left connected, but some form of multipole relay or contactor should be used.

Thanks Derek for your feedback.

for the sake of clarity, if I understand correctly, I have to use a three-position switch having central zero, with 11 poles connected as follows:
1) + sleep/"off switch" wire
2) drive solenoid/motor A wire
3) drive solenoid/motor B wire
4) + bypass/clutch wire
5,6,7) for red, green, and blue wires of the rudder sensor
8,9,10,11) for the red, green, yellow and blue wires of the compass sensor

best regards
Hi mm@maume.it

Thank you for your feedback, this raises several points.

Using the sleep switch does not power cycle the course computer and so this will trigger unusual effects with the fluxgate compass particularly.

Personally I would recommend fitting a separate fluxgate compass and rudder reference unit to each course computer and I would also switch the main power to each computer as well.
Hi Derek

thanks for your valuable support.
Best regards
Hi Maurizio,
you're welcome!
Hi Derek,

I got an idea, reading at pag. 26 of "SPX-10, SPX-30, SPX-SOL Course Computer Installation instructions 87072-3-EN.pdf".
Is it possible to use a diode 1N4004 on each contact Solenoid A & B of both Course Unit (as in the picture at page 26) instead of the switch to prevente the back-feeding?
Best regards
HI Maurizio,

You could, however, it is important to check the Diodes do not allow ANY voltage back into the computer drive output.
Reference URL's