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Subject: RE TWL: redundant instruments
From: Michael Slater (mike@XXX.XXX)
Date: Fri Mar 01 2002 - 03:39:41 EST
Jim wrote,
"My question relates to having the ability to switch GPS data to the other
instruments, autopilot, etc. so that I can use either the Northstar or the
Garmin for navigation functions as well as to have a back up in the event
either GPS receiver would fail.
Anyone have a set up like this or know how to wire it through a selector
switch or some other way of accomplishing this?"
Jim,
I have a fully redundant system along the lines you are considering. I have
2 Raymarine 300 WAAS GPS's, and a Garmin handheld, semi hard wired. I take
NMEA from all three to a 3 way switch which then distributes position info
to the rest of the system. I am therefore able to identify any errors by
comparing data.
The resultant NMEA position feeds to a Raymaine 631, and RL80. The 631 is a
dedicated chartplotter and the RL80 is a Radar and chartplotter. On the
upper helm I have a 530, and RL70, both HSB'd to the lower units. So I have
3 chart options and 2 Radar all independent, but inter connected. The
resultant XTE etc data goes thro another switch to the Auto pilot, a Simrad
AP20. So I can select the unit commanding the pilot, although in practice
seatalk throws that info all around, but is useful if you want to switch off
some units etc. Alternate switchable power is also available.
The NMEA also goes into my Navtex, an ICS Nav 4 with paper printout. This
runs a log for me every 15 mins when on passage, so if all fails I know
where I was no later than 15min previous. The NMEA also goes into the DSC
VHF.
Clearly having a handheld in the loop enables its instant removal and
operation on batteries if needed.
I also have a Sony VAIO, which runs Raytech, now V4, which I have receiving
and sending over the seatalk, however as a nav tool I have to say I prefer
the proprietary Raymarine kit. So I use the Sony as a 'plan at home unit',
and let it sit ticking away in the background when cruising.
Hope this helps your thoughts.
Michael Slater
MY Sally Lillian
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