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Old 16-01-2011, 08:28   #16
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Lets not confuse the originator of this thread. All he wants to do is switch a couple of miliamps on an LED mast light although I don't really know why a switch is needed at the mast base. I suspect the light is already on a proper circuit breaker and controled by a switch somewhere (binacle?). If he needs a switch - go to West and buy a marine rated switch. The packages are clearly labled as to the configuration. You can panel mount and thread on a water-proofing condom if its outside. All of these will easily handle the load.
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Old 16-01-2011, 09:32   #17
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DPDT Rocker Switch, On-Off-On rated 10/15/20/25A at 12VDC

“Carling” Sealed Rocker Switches ➥ Carling Tech: Rocker Switches

Blue Sea Systems
#8220/8286 ➥ Waterproof Contura Switches - Blue Sea Systems
#4155 ➥ WeatherDeck™ Toggle Switches - Blue Sea Systems
#8211 ➥ Panel Switches - Blue Sea Systems

Paneltronics #001-699 ➥ Switches Rocker Switches

Cole Hersee #56006-01 ➥ Cole Hersee Co.
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Old 16-01-2011, 09:41   #18
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Bebi's 2-wire Navigation Light Switching
Using two wires to switch either one of two lights

Navigation Light Switching for Vessels Under 20 Meters

See ➥ Navigation Light Switching for Vessels Under 20 Meters - Resources - Blue Sea Systems

Or ➥ S.P.D.T. Switch Cct - Same switch for Bilge Pump Auto / Test On, as for Combination (Anchor / Tri-Colour) Lights. Note that the toggle 'Up' (A) position, closes between the middle common and... Cruisers & Sailing Photo Gallery
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Old 16-01-2011, 10:08   #19
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A resistor-capacitor network called a "snubber" can be connected in parallel with a switch contact to reduce contact arcing.

Wetting current is the minimum amount of electric current necessary for a switch contact to carry in order for it to be self-cleaning. Normally this value is far below the switch's maximum current rating. Accordingly, switches with vastly overrated (for the application) contacts should be avoided.
Gee, Gord, I am so glad you straightened that out in my mind
BTW thanks for all the contacts for the 12 V switches but unfortunately I live in Oz. I like the Contura switches but West Marine wanted to charge me $80 just for freight to here.
I have been busy ggogling but 12 V DPDT , centre off switches seem very hard to find downunder. I have been to four large auto supply places and the children serving there look at me like I am speaking jibberish.
Into the Too Hard Basket (THB) with 12 V switch- so I will give the 240 V one a go.

I need the DPDT switch so I can run the anchor light off the same wiring as the nav masthead light, as per Bebi's wiring diagram.
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Old 16-01-2011, 11:00   #20
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Lifetech, other engineers and manufacturers disagree with your dertaing:

"DC Rule of Thumb
For those switches that list an AC voltage rating only, the "DC Rule of Thumb" can be applied for determining the switch's maximum DC current rating. This "rule" states the highest amperage on the switch should perform satisfactorily up to 30 volts DC. For example, a switch which is rated at 10A 250VAC; 15A 125VAC; 3/4HP 125-250VAC, will be likely to perform satisfactorily at 15 amps up to 30 volts DC (VDC)."
[from Products - Switches - Learn More ]

I suspect you are not compensating for the radical difference in the voltages. Dropping down from 240VAC to 12VDC makes a big difference.
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Old 16-01-2011, 11:55   #21
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Quote from GordMay:

A resistor-capacitor network called a "snubber" can be connected in parallel with a switch contact to reduce contact arcing.

Wetting current is the minimum amount of electric current necessary for a switch contact to carry in order for it to be self-cleaning. Normally this value is far below the switch's maximum current rating. Accordingly, switches with vastly overrated (for the application) contacts should be avoided. Attached Images


Right again Gordie. You must be a secret electrical, mechanical & chemical engineer!!!

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Old 16-01-2011, 12:03   #22
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Originally Posted by Nicholson58 View Post
Lets not confuse the originator of this thread. All he wants to do is switch a couple of miliamps on an LED mast light although I don't really know why a switch is needed at the mast base. I suspect the light is already on a proper circuit breaker and controled by a switch somewhere (binacle?). If he needs a switch - go to West and buy a marine rated switch. The packages are clearly labled as to the configuration. You can panel mount and thread on a water-proofing condom if its outside. All of these will easily handle the load.

Nicholson-- Yes I understand but Gordie is right pointing out that there is a minimum current and for that matter a voltage to make the contacts "make"

For example, if you take a box of common household toggle switches and check for continuity when the switch is in the on position using a high impedance ohm meter, you might find some with no continuity even though the switch is actually a good switch when 120 volts is applied.

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Old 16-01-2011, 12:08   #23
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Lifetech, other engineers and manufacturers disagree with your dertaing:

"DC Rule of Thumb
For those switches that list an AC voltage rating only, the "DC Rule of Thumb" can be applied for determining the switch's maximum DC current rating. This "rule" states the highest amperage on the switch should perform satisfactorily up to 30 volts DC. For example, a switch which is rated at 10A 250VAC; 15A 125VAC; 3/4HP 125-250VAC, will be likely to perform satisfactorily at 15 amps up to 30 volts DC (VDC)."
[from Products - Switches - Learn More ]

I suspect you are not compensating for the radical difference in the voltages. Dropping down from 240VAC to 12VDC makes a big difference.

That is utter nonsense. If a switch interrupts a DC current in an inductive circuit without an arc protection circuit in place, it is likely to arc. And if the inductor is large, it WILL arc. Be careful of "rules of thumb."

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Old 16-01-2011, 12:17   #24
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Gee, Gord, I am so glad you straightened that out in my mind
BTW thanks for all the contacts for the 12 V switches but unfortunately I live in Oz. I like the Contura switches but West Marine wanted to charge me $80 just for freight to here.
I have been busy ggogling but 12 V DPDT , centre off switches seem very hard to find downunder. I have been to four large auto supply places and the children serving there look at me like I am speaking jibberish.
Into the Too Hard Basket (THB) with 12 V switch- so I will give the 240 V one a go.

I need the DPDT switch so I can run the anchor light off the same wiring as the nav masthead light, as per Bebi's wiring diagram.
Try Jaycar.
Cat no ST-0576 add a rubber boot to help waterproof

Or electric boat parts in sydney.
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Old 16-01-2011, 13:21   #25
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Originally Posted by hellosailor View Post
... "DC Rule of Thumb
For those switches that list an AC voltage rating only, the "DC Rule of Thumb" can be applied for determining the switch's maximum DC current rating. This "rule" states the highest amperage on the switch should perform satisfactorily up to 30 volts DC. For example, a switch which is rated at 10A 250VAC; 15A 125VAC; 3/4HP 125-250VAC, will be likely to perform satisfactorily at 15 amps up to 30 volts DC (VDC)." ...
Ill certainly bow to the expertise of Carling, especially regarding their products. Id be careful about applying their 30VDC Rule of Thumb to products of unknown quality.
Products - Switches - Learn More
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Old 16-01-2011, 13:26   #26
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Ask Cole Hersee, Australia & New Zealand*, where you might locate a Cole Hersee #56006-01 (or equal) switch.

* Britax Automotive Equipment
79 Crockford Street
Northgate, Queensland 4013
Email: bae@britaxae.com.au
Tel: 61 73000 1900
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Old 16-01-2011, 15:23   #27
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Gird-
" I’d be careful about applying their 30VDC Rule of Thumb to products of unknown quality."
Yup. But we come back again to the point here: The OP has switches rated for 20x higher voltage and 5x higher amperage than he needs. All of which is so far beyond his needs that the finer points of engineering can be simplified out of the picture. A household lighting switch is generally overkill for nav lights, and that goes all the more so so an LED nav light.
As if I think any two-buck Made In China 12vdc switch from Rat Shack or other sources is going to hold up any better? Haha, engineering, right, might as well be Greek Mythology these days. Heck, I've got "JAN" WW2 surplus switches that are still working very nicely, bought on Radio Row before there was a WTC. It's just a wee bit harder to find them on any market at any price these days, isn't it?
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Old 16-01-2011, 16:07   #28
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Gird-
... The OP has switches rated for 20x higher voltage and 5x higher amperage than he needs. All of which is so far beyond his needs that the finer points of engineering can be simplified out of the picture ...
If you say so.
I might be tempted to argue otherwise, but I've forgotten more about switch technology than I can recall.
As I said, I'd certainly accept a manufacturer's advise on their product.
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Old 16-01-2011, 17:36   #29
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Marine LED Masthead and Running Light Bulb Replacement Assembly

0.16 AMPS AT 12 VOLTS
Does anyone really think that any marine DPDT toggle switch (or automotive) will fail to make or break this circuit? The mechanics of the switch will wear out before any electrical difficulty shows.

WEST switch & water resistant cover I just bought for my LED compass light 0.05 amp. This will work. You can also shop Grainger or McMaster Carr or many other electrical, preferably marine, sources.
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Old 16-01-2011, 17:59   #30
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BTW thanks for all the contacts for the 12 V switches but unfortunately I live in Oz.
I have been busy ggogling but 12 V DPDT , centre off switches seem very hard to find downunder.
svstrider, there are numerous places in Oz where you can buy DPDT switches. It sounds like you just don't know where to look. Just a few suppliers you can try are-
Jaycar electronics
Altronics
RS Components
Farnell Components
John R Turks
TLE Electrical
There are plenty more but the above all have sales offices in most states.
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