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Old 18-12-2016, 16:33   #16
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Re: Wiring compass light to two separate circuits

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Diodes shouldn't be needed. As your trilight and lower running lights are on separate switches it is easy. The output of both switches goes to their respective loads as well as the positive of the compass light. As long as the lower running lights are off the current cannot run through the switch to them when the compass light and trilight are on - and vice versa.
incorrect
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Old 18-12-2016, 16:35   #17
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Re: Wiring compass light to two separate circuits

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incorrect
You are correct, I was wrong.

A DPDT switch is one solution, one side for the compass light on each throw.

Or a separate switch for the compass light.
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Old 18-12-2016, 18:50   #18
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Re: Wiring compass light to two separate circuits

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You may want to check the value of your diodes? They may be to large thus allowing some bleed for the LEDs. Just a thought.

I hadn't thought of that!!! They are fairly sizable diodes, like 200 watts large (it's what I had handy).
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Old 18-12-2016, 19:39   #19
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Re: Wiring compass light to two separate circuits

If you want free diodes for the job, bust open any old wall wart, the heavy kind.
They will have four diodes in a bridge, rated at one amp.
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Old 19-12-2016, 03:00   #20
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Re: Wiring compass light to two separate circuits

I am interested... what is a wall wart?
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Old 19-12-2016, 03:45   #21
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Re: Wiring compass light to two separate circuits

I found the inability to switch on my compass light without the navigation lights On, being a big deficiency.
I'll put a remedy on it.

Why is standard practice such a dull one?
Why was a well built 54' boat fit with simply one compass only?

Maybe, to allow current owner to add two more compasses, both below deck and on the companionway, as l did??
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Old 19-12-2016, 04:23   #22
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Re: Wiring compass light to two separate circuits

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I am interested... what is a wall wart?

The big brick you plug into the wall that converts 110 (or 220 if you're European) into D.C. Power. The diodes in it are used to rectify the current to D.C.
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Old 19-12-2016, 07:43   #23
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Re: Wiring compass light to two separate circuits

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Originally Posted by mitiempo View Post
Diodes shouldn't be needed. As your trilight and lower running lights are on separate switches it is easy. The output of both switches goes to their respective loads as well as the positive of the compass light. As long as the lower running lights are off the current cannot run through the switch to them when the compass light and trilight are on - and vice versa.
If any one switch is on all running lights will be on.
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Old 19-12-2016, 09:24   #24
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Re: Wiring compass light to two separate circuits

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If any one switch is on all running lights will be on.
Yes, admitted I was wrong yesterday. A DPST switch is the solution or a separate compass light switch.
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Old 19-12-2016, 09:48   #25
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Re: Wiring compass light to two separate circuits

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Yes, admitted I was wrong yesterday. A DPST switch is the solution or a separate compass light switch.
I am not going to take the time to look at that, it isn't that important. I would leave the compass light on it's own switch.
There can be a situation where it may be a distraction to visibility.
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Old 20-12-2016, 08:28   #26
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Re: Wiring compass light to two separate circuits

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I am not going to take the time to look at that, it isn't that important. I would leave the compass light on it's own switch.
There can be a situation where it may be a distraction to visibility.
Many compasses have a sun shield one could just close if the light was bothersome. If it is dark and not lit, one cant see it anyway.
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Old 20-12-2016, 08:38   #27
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Re: Wiring compass light to two separate circuits

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Why are some making a simple two diode fix a major electrical rewiring? If the LED has a little bleed going to it, find better diodes or don't worry about it.
The 2 diode fix may not be the best solution, depending on user needs. It is one of many possible solutions, each with their pros and cons.

A con of the 2 diode fix is the bleed of current (albeit small) from the navigation light, making it theoretically dimmer, and possibly (though unlikely in most circumstances) to the extent it no longer meets ColRegs.

Another con of the 2 diode fix, is the diode voltage drop (.7 Vdc for standard silicon), dimming the compass light, which may be undesirable.

Art of Problem Solving 101, "Man cannot solve one problem without creating another."
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Old 20-12-2016, 09:02   #28
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Re: Wiring compass light to two separate circuits

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The 2 diode fix may not be the best solution, depending on user needs. It is one of many possible solutions, each with their pros and cons.

A con of the 2 diode fix is the bleed of current (albeit small) from the navigation light, making it theoretically dimmer, and possibly (though unlikely in most circumstances) to the extent it no longer meets ColRegs.

Another con of the 2 diode fix, is the diode voltage drop (.7 Vdc for standard silicon), dimming the compass light, which may be undesirable.

Art of Problem Solving 101, "Man cannot solve one problem without creating another."
You are bringing up red herring false problems.

The 'bleed of current' as you call it, is much less than wiring the compass light in parallel with the nav lights. Something like a few microamps in a circuit which was designed for 5 amps. Truly negligible.

Depending on whether you have dead batteries or are running the engine, the supply voltage will range from 11 volts to 14 volts. If you lose 0.6 volts in the diode, that leaves you with 10.4 to 13.4 volts to drive the compass led which can take a maximum of 2v.
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Old 20-12-2016, 10:10   #29
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Re: Wiring compass light to two separate circuits

The compass light requires little current. A diode with less requirement for forward current is going to have less reverse current "bleed someone didn't like". Low voltage logic would never work if it didn't apply.
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Old 20-12-2016, 10:32   #30
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Re: Wiring compass light to two separate circuits

Wow, thank you for all of the responses. I had originally asked because I've run out of breakers on the panel. Ideally it would nice to have it on a separate circuit. I'm planning to install a new panel with significantly more space after this season. For the time being I might just keep it separate and wire a switch with an inline fuse.
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