Author Topic: Lighting power supplies and wiring  (Read 1857 times)

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Terence

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Lighting power supplies and wiring
« on: August 27, 2014, 08:06:50 »
I've made a mast from brass tube for the Billings Nederland I'm building, and using LEDs for the lights.  Most commonly available equipment wire is too thick to do a neat job and get all the cables inside the tubing (although I'm using the mast as earth return), and I've found that wire wrap cable is ideal at about 0.25 mm diameter. 
Many LEDs require around 2.5V - 3.5Vdc, and rather than use dropping resistors for each lamp, I'm using a dc - dc converter, costing about 10.  It will take any dc input voltage from 9V to 35Vdc, and has a 500mA output at 3.5Vdc.  The lamps are then wired in parallel.  The converter is 17.5 mm x 8.5 mm x 11.5 mm, so it's easy to find a convenient location for it.  I believe there are other converters that will operate on 5Vdc.

Calimero

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Re: Lighting power supplies and wiring
« Reply #1 on: August 27, 2014, 08:15:48 »
Do you plan on remotely switching the lights ?
Are you going to arrange  in different groups or circuits (ie: nav lights, deck lights, towing lights ...) ?
If you do, check whether the switching unit

At first I had all my LEDs' negative poles in common. And I would switch each circuit on the positive pole.

Except that I had failed to notice that on my multi switch it's the positives that were in common while the unit switched the negative poles ... Wouldn't have worked !

Terence

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Re: Lighting power supplies and wiring
« Reply #2 on: August 29, 2014, 09:33:36 »
Calamero
Thanks for that.  I haven't got that far yet, but yes, I intend to have lighting in groups, and will put switches and connectors in storage lockers etc.  Problem is, if I ever get round to finishing the construction and actually using it on water, I'll have to work out how to make everything water-tight.  Not impossible, but will require careful design.  Assuming that I will float the tug eventually, after a few trials I'll probably put it in a display case and have alternative switching for the lights.  Which needs alternative circuits installed during the build that can be plugged in later.  All sounds a bit too complicated, so I might review my plans ...
Thanks
T

butchalline

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Re: Lighting power supplies and wiring
« Reply #3 on: November 15, 2014, 17:11:58 »
The "dropping" resistors are not for dropping voltage, they are used to limit current flow.  Once the LEDs conduct, they are basically a short circuit and require a resistors to limit the current going through them.

Have a look here:  http://www.quickar.com/ledbasics.htm