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model 10 · 08-05-2013, 09:12

I bought this nice little 10w 550 lumen LED AC floodlight at the boat show. Well made and very bright and 1/3 the cost of a nice DC light. Good DC LED flood lights start at about $180. I have plenty of ac power sitting around doing nothing from 2 different inverters, so why not an AC spreader light? Pretty simple change in the wires on my boat. Is there something I should be thinking about with having ac running around the boat?
We leave the small clean inverter on, most of the time so it would be a matter of another amp or so and I might want to leave the thing on when ashore sometimes..

**skipmac** · 08-05-2013, 09:26

Are you sure the light needs AC to operate? An LED only transmits current in one direction so powering by AC it would light the bulb on half of each cycle.

Also there must be some sort of transformer to drop the AC voltage as running straight wall power to an LED bulb would instantly fry it.

Most likely there is some sort of power conversion in the light that turns the AC into DC or at the very least low voltage DC. If you can figure out what that is you might be able to run the light straight off your 12V DC system.

model 10 · 08-05-2013, 10:05

Yes it has a transformer and taking it apart to change things is not what what I want to do. My complaint about all these high powered dc led's is they are junk They don't last, total rip off, so far anyway.
Why you would change ac to dc to power a light is beyond me but it makes them dependable for some reason.

model 10 · 08-05-2013, 10:26

Ok I took it apart. The single LED runs on 56.5 vdc. Thanks for the idea though.

**skipmac** · 08-05-2013, 10:44

Well I have not had problems with LEDs that are powered directly from DC. Maybe not the LEDs but your power. They are sensitive to high voltage, spikes and such. The cheap LEDs just have a resistor to drop the DC voltage to the approximate level needed to drive the LED but that voltage can fluctuate a lot when your charger is on or not, engine/alternator charging or not.

So is the transformer a wall brick or built into the fixture? If it's a wall brick very simple to find out the output and decide if it's worthwhile trying to wire direct.

**skipmac** · 08-05-2013, 11:44

Quote:

Originally Posted by Guy

Ok I took it apart. The single LED runs on 56.5 vdc. Thanks for the idea though.

Well I long ago learned to never say something is impossible since I have been proved wrong more than once, but and LED that operates directly on 56.5 VDC? I have never heard of such. There has to be some internal circuits or something that drops that voltage to something like 5 VDC. Sure you didn't miss a decimal point on the meter and it said 5.65V?

model 10 · 08-05-2013, 11:56

5.56vdc, How about that. How do I get 5.56vdc without a resistor?

**skipmac** · 08-05-2013, 12:18

With a mini voltage control circuit like the ones built in to the $35 Sensibulb LEDs.

That's why the "good" LEDs cost so much.

Or you could do the resistor in series technique which works pretty well, is a lot cheaper but you will burn out he LED sooner than the expensive ones. But how many $5 cheapo LEDs will you replace while waiting for the $35 good one to burn out? May be less expensive to go with the cheapos and swap them out when they die.

Another alternative to try, hook 2 or three of these in series. That was, at least theoretically, each light would get 1/2 or 1/3 of the voltage supply.

rwidman · 08-05-2013, 13:48

Quote:

Originally Posted by Guy

I bought this nice little 10w 550 lumen LED AC floodlight at the boat show. Well made and very bright and 1/3 the cost of a nice DC light. Good DC LED flood lights start at about $180. I have plenty of ac power sitting around doing nothing from 2 different inverters, so why not an AC spreader light? Pretty simple change in the wires on my boat. Is there something I should be thinking about with having ac running around the boat?................

Well yes. Make sure all your 120 volt AC wiring is properly installed with the correct overcurrent protection in the appropriate location. Don't be tempted to just disconnect some existing DC wiring and connect it to the inverter and spotlight. Use the proper gauge of jacketed marine grade triplex cable with white, black, and green conductors. Use 120 volt AC receptacles and place them and any splices in approved boxes. Secure the cables as provided for by ABYC specifications.

Fortytwo · 08-05-2013, 13:53

http://www.cruisersforum.com/forums/...ink-85356.html

Amazon.com: White LED Underwater Light 600L: Sports & Outdoors

model 10 · 08-05-2013, 15:27

This was easy. I bought a 12-5vdc step down power supply to replace the 120vac power supply. Fits in same little space, $12. Thanks for the heads up skipmac.

**skipmac** · 08-05-2013, 15:29

Quote:

Originally Posted by Guy

This was easy. I bought a 12-5vdc step down power supply to replace the 120vac power supply. Fits in same little space, $12. Thanks for the heads up skipmac.

Cool. Where did you get the power supplies?

model 10 · 09-05-2013, 09:16

The voltage regulator is a Pololu 5v 3a. 90% efficient. I suppose if I pot it in silicone where the 120v job was that will be enough of a heat sink?

**skipmac** · 09-05-2013, 11:49

Well if it's the kind of silicone that I'm thinking about that would probably insulate and build heat instead of dissipate. Also I would make sure what kind and grade of silicone it is. Some I think are acidic and might actually corrode the electronics. Maybe a hands electronics expert can chime in on this.