12 Volt Tap for Instruments

[fred miller]

I'm adding a new wind instrument to my complement of a depth and a speed ST 50s. It will be mounted right along side of the others.[there is an existing hole where the old wind instrument was]. I know about running the cabling to the mast head for the wind direction and speed indicator, but can I tap into the 12 volt feed that powers one or the other of two existing instruments to save the chore of having to run new wiring all the way back to the 12volt panel?It really does not matter to me if the new and the old instruments fire up simultaneously [I don't need separate switches]. Is this advisable? Do I run the 12volt feed from either one of the two existing instruments to a terminal strip and then branch off to the new instrument or tap directly into the terminals on either of the existing instruments? Should I fuse the + side of the new feed? What guage wire? Any other ideas?Someone mentioned wiring in parallel vs series, what does that do for me and what does it mean?Help is always welcome . .Fred MillerS/V M-Squared

 

[Jim Covey]

Total current draw

It shouldn't be a problem to simply tap your new power off the existing as long as the total current draw doesn't exceed your fuse (check the owners manuals for both and add the total max amperage).You probably would want to avoid this method with radios as you might get some power fluctuations and interference when transmitting but these instruments should have a steady current draw.If you do this, tap positive to positive and negative to negative. When you do this both instruments will be on the same fuse so additional fusing shouldn't be necessary but won't hurt anything either.As to wire size, again look at your expected current and size accordingly (I would guess 12 guage).Good luck,Jim

 

[Claude L.-Auger]

ST-50 has Sea Talk

And you can simply plug into one of the others. In fact, your speed and depth are probably already plugged that way. Check the wiring instruction of your wind meter and it will probably confirm this. I used to have the same set-up on my previous boat and that's the way it was. I installed ST-60 Wind, Speed and Depth on my current boat and they are also hooked together for power as per Ray Marine instruction. Good luck

 

[Jeff Bacon]

Claude is right - caveat

It sounds as if all of your instruments will be ST 50's. If so, no problem with the Sea Talk connections. However, if you mix newer with older instruments you may need different cableing. The older Raymarine instruments utilized a round plug, while the newer ones utilize a square plug (or vice versa ?). You just need to get an adapter if that is the case. Either way, Sea Talk should work just fine for cascading your instruments. One final note....if you make use of an autopilot, that instrument may need to be the "first one" in line with the others linked from that one.Good luck.....Jeff

 

[fred miller]

I May Have Been Misleading

Everyone's input with this, as always has been super. . BUT . .the problem is the new instrument I'm connecting is not an ST 50 like my others. It is a different brand [SR Mariner / Round Dial] not even NEMA capable. In a nutshell, the story is, this unit is a factory warranty replacement for the orginal wind instrument which was solar powered [that's right, solar powered !] and didn't work correctly. SR replaced it with a 12 volt powered model and the complete new mast head unit.The price was right so I didn't upgrade to fancier stuff. And no, I didn't install this stuff in the first place or I would have kept everything ST-50 series.Obviously the SR does not have Sea Talk capability so the connectors are not going to be the same. In fact, there are no connectors on the SR, only two binding post screws for the + and -, 12 volt input leads. So the question remains as to how [or where] can I tap power? From the ST-50s? Fred Miller

 

[Claude L.-Auger]

I would connect separately

Since your instruments are not the same brand, to avoid future warranty problem I would connect the new SR wind on its own. And of course install the recommended fuse in the pôwer line. That way, if anything goes wrong, manufacturers don't have the possibility of avoiding the issue because of "mis-matched" instruments. Good Luck