Smartcraft wiring question...

[matthewmiller01]

Why do you need terminating resistors on the unused ends of harnesses, or are they, in fact, needed at all? :huh:

Thanks in advance!

 

[Brian's Song]

You need to put terminating resistors on data lines. The data signal is a series of pulses that travel the wire at the speed of light. When they reach the end of the wire (with no terminations) it's like hitting a brick wall and they reflect back in the opposite direction. This causes noise and data errors. Putting terminating resistors on is like providing a truck escape ramp. The signal slows to a stop and doesn't bounce back.

 

[matthewmiller01]

You need to put terminating resistors on data lines. The data signal is a series of pulses that travel the wire at the speed of light. When they reach the end of the wire (with no terminations) it's like hitting a brick wall and they reflect back in the opposite direction. This causes noise and data errors. Putting terminating resistors on is like providing a truck escape ramp. The signal slows to a stop and doesn't bounce back.

...and that is why I love this forum. People know the answers to what is Greek to me. Thanks (although now I'll have to wait a little longer to connect my genny to the Vessel View). :smt013

 

[Henry Boyd]

You need to put terminating resistors on data lines. The data signal is a series of pulses that travel the wire at the speed of light. When they reach the end of the wire (with no terminations) it's like hitting a brick wall and they reflect back in the opposite direction. This causes noise and data errors. Putting terminating resistors on is like providing a truck escape ramp. The signal slows to a stop and doesn't bounce back.

That is completely correct. However some cables have built in resistors on either the ends, or just one end, making an add on resistor necessary. This also only applies to to the trunk cables on the end that terminate. For example a trunk cable that runs from engine to a lower station and then to an upper station would not be terminated at the lower station.
Henry


Sent from my iPad using Tapatalk HD

 

[matthewmiller01]

So would it hurt anything to connect the harness to check functionality (and leave it connected provided there were no issues) and then add the resistor later once I get it (its currently on order)? Or could I damage something irreparably?

 

[Henry Boyd]

I doubt it will damage anything, as Brian points out the resistors act as buffers to absorb the data packets once they have reached the end of the network. I also suspect nothing will work because of the reflected old data.

henry

 

[kaz911]

you should not damage anything but you might get "funny" things happening on your screen if it is not terminated correct.

SmartCraft has 3 individual CAN bus circuits. The one you are "playing with" is the CAN-V part of it - and that is only for displays and instruments & data exchange etc. The 2 other CAN bus circuits are isolated for engine controls etc. (as far as I know - SmartCraft service manual still on order...

But please check with Kohler - I think your Genny has a built in terminator for all the CAN circuits. My Kohler is connected to the "red/green" new type junction box - and did not have terminators on the Kohler end. But since I don't have the service manual - I can't tell you if that is correct. But the Kohler info on the VV display is @ nice to have @ - but you can't start/stop the generator from it

 

[kaz911]

Just a little update...

IF you have the Ba**s - you can check if things are terminated correct

Turn EVERYTHING off!! - batteries OFF at battery switch - keys OUT off the ignition etc.



Above is a picture of a SmartCraft Terminator - where I have indicated the terminating resistors. (There are 2 resistors in mine)

On the cable that comes OUT of your Genny - I think there are only 2 wires in the connector. With everything turned OFF - if you measure OHM with a Multimeter on those two wires - and no other cables plugged in - it will show around 120 Ohm if it is terminated inside the genny.

If it shows --- Ohm or MOhm etc - it is NOT terminated inside the Genny.

Next - plug in the SmartCraft harness. If I'm right - then you have a spare connector on the smart craft harness. Measure again Ohm on the same "pins". Now that there is a completed circuit - if the Ohm reading shows 60 Ohm - you have 2 resistors somewhere in the circuit and your Genny does not need a Terminator.

If it shows 120 Ohm - you need an extra terminator at your Genny Side. (two 120 Ohm resistors in parallel = 60 Ohm - which is what it is supposed to be.)

 

[kaz911]

Sorry - scratch the above.... The terminator I showed was the Engine/Control system terminator - as I said - there are 3 CAN bus circuits on SmartCraft.

here is the right one. The engine system shown in the picture above has 2 can bus connections - ergo - 2 terminators I learn everyday....




And my 5ECD Genny IS terminated inside with 120 Ohm. And attaching a Terminator to the "end" that sticks out of the extension cable by the Genny - will have no effect at all - on mine the pins show above is not followed out into the male end of the cable (female end goes in genny connector)

 

[matthewmiller01]

So I still do not have this hooked up. :smt013 I have the genny to helm harness and one of the adapters but not the other one. It seems Sea Ray forgot to order it when I told them to. So I am still unsure if it will even work. Looking at it, I think I may have been sent the wrong (male vs. female) adapter. If this is true, I have the million dollar question... Can I make some connections the old fashioned way - by splicing? I know it may not be the best way, but assuming my install will be permanent, will it matter?

 

[matthewmiller01]

Henry? Kaz? Any ideas on my questions? Help!

 

[Henry Boyd]

Sorry Matt,

I must have missed your last post. I don't really know the answer to your question. I do know that the plugs and plug parts are common automotive parts and many people in the car business build their own cables. That suggests that taking a male-male cable and a female-female cable, cutting them in half and splicing them into two male-female cables would work.

I assume though you are talking about removing the generator plug from the helm-generator cable and wiring it into the gen's wiring harness. I've never taken a cable apart, but I suspect these are pretty thin wires (24-26 ga?) combine that with the marine environment and I'm not sure how long it would last. Personally I'd wait for the right parts.

If you have the part number for the missing part you might try eBay, or FP, or Great Lakes Skipper.

Henry

 

[matthewmiller01]

I just called Mercury Marine and got them to send me the following diagram, showing part numbers.

 

[matthewmiller01]

I guess I still need one more piece. :smt013