Joining GPS cables

erbster

erbster

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I would be grateful for some advice please.

I have a garmin GPS 76 mounted inside the cabin of my small boat. It feeds a dsc VHF and a GPS repeater. It also feeds yeoman sport plotter, which proved to me it all works, but having altered the wiring, the connection is not reliable.

Is there some kind of standard connector to join these cables? At he moment, I have just soldered them together in a rather ugly union, but as I am joining 4 devices, its hard to solder them all together reliably.
 
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Assuming you are talking about nmea data, not the RF, using choc blocks with a few bits of tinned wire to common the terminals should work.
Or you could put some solder pins into a strip of vero board or similar and solder the wires to that.
One driver driving 3 receivers is not ideal but usually works.
 
lw395 said:
Assuming you are talking about nmea data, not the RF, using choc blocks with a few bits of tinned wire to common the terminals should work.
Or you could put some solder pins into a strip of vero board or similar and solder the wires to that.
One driver driving 3 receivers is not ideal but usually works.
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Both very good suggestions. Low cost too (ie have the bits knocking about...)
I was not sure it would work, so made a trial connection, which worked fine. Now I want a more permanent job
Thanks for those tips.
 
I have a GPS72 in the cockpit connected to a computer down below to it's USB hole through a RS232 to USB converter. I first wired it up using a bit of household flex with bodgy soldered joints which sound like yours. It worked but was unreliable. In particular it lost communication whenever the engine was started. I subsequently replaced the cable and converter with a manufactured one which was long enough and shielded from end to end. It is now reliable. I do not know whether the proper cabling made the difference or whether the converter (from a different manufacturer) is simply a more robust bit of equipment. HOWEVER, I use the Garmin protocol, not NMEA, for its extra capability, and if I do use NMEA it is unreliable.

I have another one sending NMEA to the DSC radio and the AIS with bodged cabling. They work fine, but neither radio nor AIS are going to complain about short interruptions in GPS signal.
 
nigelmercier said:
Choc blocks have no place on a boat.
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geem said:
Why?
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For a start, they provide no support to the wires, so any movement is transferred to the vulnerable point where the copper is crushed under the screw. They are almost impossible to seal against moisture.

The only times they are acceptable are as a quick-fix until a better join can be made, or with the addition of ferrules to terminate the wires.
 
I largely agree with Nigel, although I wouldn't be quite so dogmatic. As he says, they're handy to have for quick fixes (or for installing a tricky circuit for testing purposes, before doing the job properly). Trouble is, quick fixes have a nasty habit of becoming permanent. Nonetheless, I usually have a few aboard. They should never be installed anywhere remotely damp (which on some boats is anywhere).

As well as the troubles Nigel cites, the freely available ones often have mild steel screws into brass, a fine recipe for corrosion. More expensive ones have stainless screws, plus a stainless spring strip which bears on the bare wire.
I agree that crimped-on ferrules make the best of a bad job. Very small ferrules can be bought which are ideal for NMEA wires.
 
2nd_apprentice said:
Interesting, my Rutland 503 came with a chock block.
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I was going to say, lots of equipment sold for use on boats comes with choc-blocks or similar terminals. Retrofit electrics panels, for instance, often have a row of big choc-block across the back with one or two terminals for each circuit. So while there are certainly better ways, and the typical green-corrosion-covered chocblock half-heartedly wrapped in decaying PVC tape in the bilge is obviously an abomination, I can't get too excited about banning them from boats entirely.

On Kindred Spirit, my NMEA connections were made using choc-block inside a plastic "project box" screwed to a bulkhead, with the cables entering from below and secured to the box for strain relief (cable ties through holes drilled in the box). This worked fine during my ownership, and I have every confidence that it will continue to work fine for many years to come.

Pete
 
prv said:
I was going to say, lots of equipment sold for use on boats comes with choc-blocks or similar terminals.
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Quite so, Pete. And lots comes with un-tinned wire, so maybe that's not the ideal example of best practice. The better choc block-type arrangements (such as those on the fridge controller I've just been re-wiring) have a copper strap beneath the screw: this, rather than the screw itself, bears on the cable.

However, I agree with much of what you say, although your meticulous approach is not universal (as anyone who's bought a used boat well knows :mad:). But, hey, that's boating.
 
prv said:
On Kindred Spirit, my NMEA connections were made using choc-block inside a plastic "project box" screwed to a bulkhead, with the cables entering from below and secured to the box for strain relief (cable ties through holes drilled in the box). This worked fine during my ownership, and I have every confidence that it will continue to work fine for many years to come.
Click to expand...

That's pretty much what I did, but using 'waterproof' boxes left over from a CCTV installation.
 
nigelmercier said:
The only times they are acceptable are as a quick-fix until a better join can be made, or with the addition of ferrules to terminate the wires.
Click to expand...

Normal ferrous ones with direct screws onto strands I would agree without reservation, just storing up trouble down the line, however, non ferrous ones used in conjunction with insulated bootlace ferrules are a perfectly valid method and permitted under NMEA0400 and BS EN ISO 13297:2012 standard, still don't like even doing it that way though.
 
Putting the choc blocks in a plastic box is a good idea.
However you join the wires electrically, securing them so the join is not under any strain or vibration is important.
I think that's more important for reliability than whether the join is a crimp or soldered or clamped by a screw.
I've seen plenty of crimping and soldering that is much dodgier than a choc block.
 
Strain relief is important, but is only part of the equation and however firm and adjacent it will not help with strands being severed by direct screw pressure in a chock block, it is not permitted under any marine standard to use this method, the rules are quite clear and for a good reason. When it works its because you've got away with it rather than done it right.

Back to the OP question, one really good way to do stuff like this, which allows for future additions and upgrades is to use barrier strips with bridges (where needed) connect to them using small ring terminals properly crimped and tested with the shank insulated and strain relieved with heat shrink. You can then stand back and look what a proper and lasting job you have done.
 
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But is the kind of person who asks the question going to own the correct crimp tools and the correct crimps for each size of wire?
That's where the 'proper' ways tend to go wrong in amateur wiring.
Having had to make this kind of thing work halfway across the channel where some Halfords or Maplin crimper has been used, I regard crimps with suspicion.
And some soldering done with 12V irons is horrific. Specially with lead free solder...
Let's face it, most things in our houses are wired with screws bearing on the wires.
It's not ideal, but it can work if done carefully, to do much better reliably needs professional tools.
Maybe the TackTick wireless instruments are the best way?
 
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