Should I use diodes?

[Coaster]

I am renewing much of the 12V electrical system on our Westerly Seahawk. The fittings being installed include a new switch panel with circuit breakers. One of the switches will control the masthead tricolour. A second will switch the pulpit bicolour, mid-height mast mounted steaming light and pushpit mounted stern light.

I would like to take a feed, from each of these two switched circuits, to the compass, depth and log instrument lights. But if I simply connect these feeds to the compass etc. lights, current will "leak" from one switched circuit to the other.

Should I use a couple of diodes, one in the feed from each switched circuit? I gather that diodes allow current to flow one way only, subject of course to their ratings. But I have never knowingly seen a diode, let alone fitted one.

I have looked at the Maplins catalogue but the extensive range of diodes in it means little to me. Can any knowledgeable forum member advise please?

 

[seasolutions]

remember that a diode will drop abot 0.7 volts all by itself, ie use power for no return.

http://www.maplin.co.uk/Module.aspx?ModuleNo=46408

might just do the trick

 

[rivonia]

I am renewing much of the 12V electrical system on our Westerly Seahawk. The fittings being installed include a new switch panel with circuit breakers. One of the switches will control the masthead tricolour. A second will switch the pulpit bicolour, mid-height mast mounted steaming light and pushpit mounted stern light.

I would like to take a feed, from each of these two switched circuits, to the compass, depth and log instrument lights. But if I simply connect these feeds to the compass etc. lights, current will "leak" from one switched circuit to the other.

Should I use a couple of diodes, one in the feed from each switched circuit? I gather that diodes allow current to flow one way only, subject of course to their ratings. But I have never knowingly seen a diode, let alone fitted one.

I have looked at the Maplins catalogue but the extensive range of diodes in it means little to me. Can any knowledgeable forum member advise please?

Why are you taking a feed from these circuits? Much better if you had seperate lines to each.

Peter

 

[VicS]

Yes a diode from each of the switched light circuits to the panel lighting circuit. Then which ever set of nav lights you have on will automatically illuminate the compass and the instruments.

The 0.7 volt drop will not be important.

I would use a couple of the 1N4000 series.
1N4001 should be adequate but just check that the total load from compass and dials wont be more than 1 amp
If it is go to 1N5400 which is rated at 3 amps.

BUT personally I like to be able switch the panel lights on/off independently so would opt for just a switch.

I would also make my nav light switching more complex so that I could use the bicolour and stern lights while sailing. (Suppose the tricolour failed or was difficult to see against the background of shore lights)
Just means a switch in the supply to the steaming light so that it does not come on automatically with the bicolour and stern.

 

[rogerthebodger]

If you use double pole switches you can feed the nav lights from one pole and the instrument lights from the other pole and no diodes will be needed.

I have a multi position switch for my nav lights fed from a single circuit breaker so that the crew cannot have an invalid combination of nav lights

 

[Billjratt]

I'm a fan of diodes, but just for the compass. the great thing is, that if you retro-fit, it liberates a switch for some other use.

 

[halcyon]

I would like to take a feed, from each of these two switched circuits, to the compass, depth and log instrument lights. But if I simply connect these feeds to the compass etc. lights, current will "leak" from one switched circuit to the other.

From around 1985, all the Powercentre switch panels we supplied to Westerly had two diodes fitted. These took power from bi lights and tr-light switch outputs and supplied power for compass and nav equipment back lighting. They also later on also powered switch legend back lighting no night use.

As there is, or was then, seperate input for back lighting on each unit, it can all be common to the one pair of diodes.

We used 1N5400 series diodes ( 3 amp ), and never had any one come back with a problem.

Brian

 

[Maine Sail]

One of the switches will control the masthead tricolour. A second will switch the pulpit bicolour, mid-height mast mounted steaming light and pushpit mounted stern light.

I am guessing you use the tri-color for sailing and the other set of nav lights for motoring/motor sailing?

Do your instruments have a separate input for lighting only or are you breaking them open to tap into this circuitry?

With the Raymarine ST-60's I can simply turn the lights off to all the displays from any one of the via the Sea-Talk network.

The compass light will likely need a diode to run off of two systems if incandescent..

 

[Coaster]

Thank you all for your replies.

I am particularly grateful to Seasolutions and VicS for giving details of particular diodes.

Rogershaw, I have already ordered the switch panel, with single pole switches.

Halcyon, I am discarding the old panel. As it's 200 miles away from where I am now, I can't give any reference numbers that may be on the panel. If you know of anyone that might want it I would be pleased to pass it on, although it seems unlikely to me that anyone would.

Maine Sail, the instruments in question are a pair of oldish Stowe wind and log displays and a new compass, all of which have specific lighting feed connections. We have a cockpit mounted Garmin 3000 chartplotter and radar display which has its backlight level controlled directly. Other instruments are at the nav table. And yes, the tricolour is for sailing and the other nav lights for motoring/ motor sailing.

I appreciate that alternative nav light arrangements may be required if individual lights fail. My reckoning is this:

1. Under sail. Tricolour fails. Turn on motoring lights and also give way to vessels under sail. Reach destination, mend tricolour.

2. Under engine. Pulpit bicolour fails. Replace bulb or otherwise repair light.

3. Under engine. Mid-mast steaming light fails. Switch on masthead anchor light (all round white) and shroud pushpit stern light or remove its bulb. That gives a forwards facing white more than 1m above the port and starboard lights (about 12m actually), and a stern facing white light, albeit in a higher than usual position. Replace steaming light bulb or otherwise repair when possible.

4. Under engine. Pushpit mounted stern light fails. Replace bulb or otherwise repair.

I'm sure there are other arrangements that would suit some people better, but this seems reasonable to me. However I'm always interested to hear other people's sensible thoughts on such matters.

I intend to visit my local Maplins tomorrow.