To diode or not to diode that's the question.

I recently bought a shiney new set of rotary switches to replace the old push/pull switches on my dash panel. I have to make a decision about the Nav/ Anchor switch. Below is a drawing of the Nav/ Anchor switch as I believe it is supposed to be wired. There is a diode crossing the posts that I think is supposed to power the anchor and indicator lights when the switch is in the Nav position:



The problem I have with this arrangement is the fact that there is voltage drop across the diode. (12.6 to 11.6) I am worried that this will cause the anchor light to dim. Being that anchor lights are supposed to be visible for 2 miles, dimming it is less than desirable. I have included here a drawing of what I would like to do to. I plan to get rid of the diode and replace it with a relay. Activating the relay with the nav lights will supply full battery voltage to all the lights, including the indicator, when in the Nav position. In the Anchor position the relay will remain open isolating the nav lights and only the anchor light will burn:



I know I am complication things a bit, but being that switch is a simple two way switch, I see no other way to get full voltage to all the lights, isolating the anchor circuit and turning the indicator on in both positions. I am fully capable of missing the most obvious things so feel free to let me know if I have made a mistake or if you may have a better way of doing it. Thanks ahead of time.

Re: To diode or not to diode that's the question.

Use a double pole switch. The ones you usually see are off in the center on in one direction and on in the other.

Here is how you would wire it up.

I am assuming that in the nav position you want all 4 lights to light up and only the anchor in the anchor position.

Re: To diode or not to diode that's the question.

I bought these switches mounted in a panel. The panel is new unused and there are 10 switches and breakers in it. They are Marineworks Rotoswitches. (iboats carries them) When I checked them, the nav/ anchor turned out to be a on-off-on switch with a diode installed. What I need is a on-off-2on switch correct? I'm not sure why they used this switch in the panel insted of a double pole.

Re: To diode or not to diode that's the question.

Dump the relay. Just more to go wrong. Use the diode and an ON-OFF-ON switch or the DPDT Bruce showed. The KISS principle applies in boating.

Re: To diode or not to diode that's the question.

How big is this diode that came with the switch? If it can carry the current, there would be nothing wrong with using the diode.

Re: To diode or not to diode that's the question.

How are diodes rated? By gauge?

Re: To diode or not to diode that's the question.

By amps.

Re: To diode or not to diode that's the question.

Here's a diagram of how that setup works. Cheap and reliable.

Re: To diode or not to diode that's the question.

Silvertip's diagram is similar to your first diagram except you had the diode in the wrong direction. Also notice that he has the diode only facing the anchor light. That way the diode only needs to be rated for current for the anchor light.

When you are stopped and achored, the anchor light will also get full battery voltage. You will have a voltage drop when in Nav position but, since the motor will be running, you will have higher voltage anyway.

Re: To diode or not to diode that's the question.

You would probably have to get down to 6-8 v before you really noticed a change in your anchoring lite's lumens. The small drop across the diode for a light application, at low wattage such as this is, is miniscule.

Mark

Re: To diode or not to diode that's the question.

Actually its the peak reverse voltage and the forward current capacity that needs to be considered. In this case the diode needs to block a maximum of about 15-16 volts (engine running) and since most are rated well above that, thats not a problem. The current rating will depend on how much current will pass through the diode in the forward direction. That's not much either -- less than 1 amp I suspect so that diode can be a garden variety. Probably a 75 cent item if that.

Re: To diode or not to diode that's the question.

All great information. Thanks much. I am going to use the switch as it is. As long as I do not notice a big drop in brightness when the nav lights are on, I agree this is the simplest setup. I like the idea of using the switches I have opposed to buying another switch.

BTW what do you think of the Rotoswitches? I like them because they are not too modern looking and they have the nifty indicators.