e120 Classic Seatalk[1] power?

[sailabroad]

My seatalk[1] network is powered from my autopilot and I just swapped out my old c120 with an e120 Classic that i got on ebay.

It's not seeing any seatalk[1] data

I noticed the seatalk red(+12 power) cable was connected on the seatalk plug which goes into the e120 chartplotter and remembered something about the network should only be powered from one end?, I think!?, but goggling everywhere even on the raymarine forums hasn't turned up anything.

Anyone know anything about this?

Thanks

[evm1024]

Originally Posted by sailabroad

My seatalk[1] network is powered from my autopilot and I just swapped out my old c120 with an e120 Classic that i got on ebay.

It's not seeing any seatalk[1] data

I noticed the seatalk red(+12 power) cable was connected on the seatalk plug which goes into the e120 chartplotter and remembered something about the network should only be powered from one end?, I think!?, but goggling everywhere even on the raymarine forums hasn't turned up anything.

Anyone know anything about this?

Thanks

You are correct that you should only power seatalk from one point (and any other bus for that matter)

With 2 power connections to seatalk you will end up with minor voltage level differences at each connection (which by its'self is not too bad), the introduction of noise sources on the power bus and "bad things" (TM) in the case of losing one of the power sources. See below.

The primary reason to power seatalk from one source only is should you power it from 2 sources then the current supplied to the bus is shared from the 2 sources. Should you lose one of the sources then all the current needed on the bus will be sourced from the single active source. This could result in an over load of the conductors on the active supply or in the device supplying current to the bus.

As an example - Let's say that you power your seatalk bus from your AP and that it has a 10 A fuse for seatalk power. All of the wires, fuse, circuit board traces are sized to supply the 10 amps max on the bus.

As you grow the system you end up installing another device that also can supply power to the seatalk bus. But this device only has wiring, fuse etc for 5 amps.

Best case when you lose the AP for whatever reason it is no longer able to supply the 10 amps. If you seatalk loads draw less than the 5 amps now available you have "no problem". But if the seatalk loads draw 10 amps it will blow the 5 amp fuse is short order and you have no seatalk instruments. Or... If your seatalk load is not too much over 5 amps it will take minutes to blow the 5 amp fuse and in the mean time you could be burning up traces in the instruments or in the power supply wires possible causing a fire.

Other variations exist.

Noise is still a significant reason not to be minimized.

[smac999]

dissconnect the red wire going to the plotter and see what happens.

I don't know if the plotter can provide power or not. gernerally it either comes from the pilot or an external 12v source. I think you're only surposed to power from the plotter if only using the GPS as it's small draw.

[sailabroad]

Thanks smac999,

Yes I disconnected the power(red) from seatalk[1] to the e120 and also tried to use it to power [just] a r125, no luck so seems unit was a dud, returning it, damn, as it was cheap guess that was a clue?

Looking into the schematics to see if there is anything i can surface level up.

[Gypsy23]

Originally Posted by sailabroad

Thanks smac999,

Yes I disconnected the power(red) from seatalk[1] to the e120 and also tried to use it to power [just] a r125, no luck so seems unit was a dud, returning it, damn, as it was cheap guess that was a clue?

Looking into the schematics to see if there is anything i can surface level up.

The C120 schematic I have shows a 500ma fuse (F9) on the +12V feed to the Red ST1 line to power ST devices. This is located on the PSU/Connector board, almost dead in the middle.

Even if this is blown, you should be able to receive and transmit data on the ST1 Data line from an ST1 device which is powered from elsewhere. If you can't get data in from a known active ST1 device there may be deeper problems.

However, I have an E120W which is different. It wants to 'see' +12V on the ST red wire in order to know ST is connected. It doesn't supply 12V to ST instruments, just senses it for a connection. Without the 12V present the E120W doesn't process ST1 data.

[sailabroad]

I found this on an archived raymarine tech forum.. after a lot of searching - Troubleshooting a SeaTalk communications failure - Printable Version - if anyone is interested or faces similar issues.

'Troubleshooting seatalk network'

- insufficient power due to having joined the red lead of the SeaTalk cable interfacing a C/E-Series Classic MFD to the SeaTalk bus ... this problem is most commonly identified in systems which feature these MFDs and either use an autopilot or dedicated circuit to power the SeaTalk bus. In such systems, should the autopilot course computer or SeaTalk bus power not be switched ON when the the C/E-Series Classic MFD(s) is in the ON power state, then insufficient power will be supplied to the SeaTalk bus, resulting in SeaTalk communications failure. The problem may be eliminated by disconnecting the red lead of the SeaTalk cable which is interfacing the C/E-Series Classic MFD to the SeaTalk bus. The cable's red lead should then be insulated to prevent shorting.