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ContinuousWave: Small Boat Electrical
Console wiring for sonar and other accessories
|Author||Topic: Console wiring for sonar and other accessories|
posted 05-31-2006 07:31 PM ET (US)
I am re-wiring my console and have purchased a nifty little 6 switch panel with newer fuses and LED indicators.
1. Why should a sonar/depth finder be wired directly to the battery as opposed to a fused panel switch?
Tight lines mates...
Electrical feng shuei here I come!
posted 05-31-2006 09:08 PM ET (US)
The only thing that should be wired directly to the battery
is the bilge pump, and then only if it has a float switch
and a fuse.
But use an adequate gauge of wiring to connect your panel to
No problem running wiring in the bilge tunnel. Just use
posted 05-31-2006 10:21 PM ET (US)
Thanks for that Chuck.
For some reason, the manufacturer (Lowrance) has recommended the straight wiring to the battery. I will check that again to make sure. I used 10 gauge wire for the connection from the battery to the panel (This is the thickness supplied by the panel manufacturer. The common ground wire that comes off the panel is very wimpy, but I used it figuring it was adequate since it was OEM.
I solved my bow light wire issue by running it all the way down the rubrail to the stern light connector. The only issue now is to tie the stern and bow light together. I may end up having to run a separate set of wires to make it simple, but am wondering about a possible 3 way switch or method to avert pulling more wire through.
Is there any problem with using some 3 way male adapters and tying into the stern light with the same switch? I thought about putting a small set of terminals at the stern like the old stock whalers had.
Any ideas or input welcomed and appreciated.
posted 05-31-2006 11:05 PM ET (US)
Things like sonar should be wired direct to battery to avoid interference from other electrical circuts. It is also recommended that an amplifier or stereo be wired directly for the same reason. I agree that on some boats the bilge should be direct wired.
posted 06-01-2006 09:54 AM ET (US)
I think I'd upgrade the ground wire too.
Your batteries are in the stern?
You have two lights, bow light, and all-round stern light,
Next time you pull a wire through the console, leave a string
posted 06-01-2006 10:52 AM ET (US)
Yes, I have the bow light, and a long 360 degree stern/anchor light. With the "center off" switch both hot wires and a common ground are wired to the switch? That makes sense.. but it might just be easier to wire the two lights separatley.
The panel is a "victory" model #AA10064LTW 6 gang lighted white. The switches are all the rubber coated toggle style. I already picked up the wire and I'll pull it through today.
I have two batteries in the console, and I also just purchased a perko two battery switch with alternator "field disconnect". that will be my next project.
Thanks for all the help.
posted 06-01-2006 07:41 PM ET (US)
I was under the assumption that only the negative grounds need be isolated to prevent any interference from parallel electronics. Is this incorrect?
posted 06-01-2006 08:08 PM ET (US)
Steve, my Lowrance said the same thing, wired direct to battery unless used in salt water, then they wanted a switch. I put mine on a switch and it has performed very well. John
posted 06-01-2006 08:20 PM ET (US)
Use a DPDT center off switch. Wire power to
both middle terminals. Wire the bow
lights to one terminal on one side. Wire the
stern light to both terminals on the other
side. If the switch has a pilot light, wire
that like the the stern light.
No need to switch the ground.
posted 06-01-2006 11:41 PM ET (US)
When instructions call for a device to be wired directly to the battery in order to reduce potential of interference (pun intended), the manufacturer probably is worried about introducing common mode power supply noise or voltage variations into the supply to his device. It would be far more appropriate if the device contained proper power supply decoupling so that it was not necessary to wire directly to the battery.
The notion that you should or could wire all devices directly to the battery is a flawed concept. There is a general rule in electrical practice that demands that only one conductor be secured under each screw terminal. Thus, in a proper installation, there ought to only be one wire or cable connector to the terminal on a battery. This wire or cable should in turn be connected to a distribution block, with proper fusing. Devices should be wired to the distribution block, and not to the battery terminal.
The concern about common mode interference is along this line. Assume there are two devices, A and B, connected to the power source and drawing their current from a common distribution line. The distribution wiring has a finite resistance R of 0.1-ohm. Let us assume that device A draws a current I of 20-amperes. This causes a voltage drop in the distribution of (20 x R) = 2-volts. Because device B is connected to a common distribution, it also sees a voltage drop of 2-volts. Thus device A can modulate the voltage to device B. If device B is sensitive to variations in its supply voltage, this fluctuation can cause interference in device B.
Also, if device A has very poor power line decoupling, it may put some noise or hash on the power line itself. This will be coupled into device B by the common power line. If each device had a separate power line, the noise would tend to be shunted away by the very low impedance of the storage battery. In this example, if each had its own power distribution with resistance 0.1-ohm, the common mode path would be via a 0.2-ohm circuit with a shunt to ground of the battery, which represents an extremely low impedance, probably on the order of 0.01 ohm. The ratio of the two (0.2/.01) would be about 1:20, and this would tend attenuate any common mode noise between the devices.
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