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The Infamous yellow wire!!

Old 07-18-2013, 06:34 AM
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Default The Infamous yellow wire!!

Hey Gents/Ladies,

Was hoping someone can shed some light in RE to the yellow wire in the wiring for BSM 2, I understand it can be used to power a switch but is it really required? Or can you just put a switch in the red/positive line, I have before hooked the yellow and red together to power with a switch..... Which still doesn't leave power going to the system at all times, Is this not right? If so can you please tell me why?

Thanks
Old 07-18-2013, 06:49 AM
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For a non MFD device you can connect the yellow wire together with the red to a switch. For a MFD, don't connect the yellow wire in this case.
Old 07-18-2013, 06:53 AM
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The yellow wire basically negates the need for a switch. So the BSM will shut off when the display shuts off. If you want to turn your BSM off at times when the display is still on then a switch for the yellow and red is fine.
Old 07-18-2013, 07:02 AM
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I have connected the yellow wires for BSM-2, StructureScan, WiFi-1 and the radar together on the same switch as I use to switch the power to my autopilot.

This way I can switch off the power consumption to all peripherals. I of course have a separate switch for NMEA 2000 power as well. When I sleep in the boat when anchored I use NSS7 as anchor watch, I use both GPS and sonar alarms. If everything had been controlled from NSS12 yellow wire I would have had three MFD's and all the peripherals draining my battery when sleeping, waking up with a flat battery.

When I leave the boat the main switch powers off everything except alarm/tracking and the diesel heater.
Old 07-18-2013, 07:04 AM
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simple version, hook the BSM yellow wire to the nss/nse yellow wire. connect the red to a fused 12v (no switch, always hot) then the bsm will turn on when the the nss/nse is turned on.
Old 07-18-2013, 11:29 AM
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Originally Posted by knotreel View Post
simple version, hook the BSM yellow wire to the nss/nse yellow wire. connect the red to a fused 12v (no switch, always hot) then the bsm will turn on when the the nss/nse is turned on.

I hooked up the yellow wire to a extra switch that I had and I turn my BSM 2 off when it's not in use.

red to main power panel
yellow to switch or main unit
Old 07-19-2013, 07:35 AM
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With talking about hooking the yellow wire to a switch, it may be obvious, but just in case it is not, that switch needs to have +12V provide to one side and the yellow wire from the accessory (BSM2, Radar, LSS, Sirius Weather module, etc), on the other.

Often if you have a bank of switches they will all be connected on a common +12V feed, other times they are each discrete switches, so if you connect the yellow wire to the switch and nothings on the other side, the it won't do much good.

Again, its probably obvious to most or all, but.....
Old 07-19-2013, 07:37 AM
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There should be fused +12V on the other side of the switch. 1A fuse would be fine.
Old 07-19-2013, 07:54 AM
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BSM-2 has an internal fuse. So as long as you have fused/have breaker for the entire 12 volt feed for the wire you are using, all is well and you don't need yet another fuse for BSM-2's power.
Old 07-19-2013, 08:10 AM
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It's a good practice to fuse external signals like the yellow wire with a low Amp fuse. It's even shown in the BSM-2 installation manual, but without recommended Apm size.
Old 07-19-2013, 08:33 AM
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I was referring to the main power lead. For yellow wire, if you like you can fuse it but it really is not necessary. I have repaired hundreds of car stereos in my day which also have the same remote power yellow lines. I don't see how the fuse would have prevented any issues there. The yellow line goes to a transistor switch. The main power to the transistor is coming from the main/red line. The yellow is just an input to it. Never seen a short in the yellow wire but if there were, the transistor will below before a 1 amp fuse will. Fusing it would be like fusing an audio input line which is never done.

So if you like you can fuse it. But it wouldn't be for any real risk . Assuming you do want to fuse it, use a much smaller fuse like 100 milliamps/0.1 amps. Be sure to carry a spare as such fuese can be harder to find.
Old 07-19-2013, 08:47 AM
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0.1A sounds good.

If it had been my design it would not have been any need for an external fuse since it would have been a Multifuse on the PCB together with the ESD and transient protection

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