Power LED underwater lights

This brief instructable will provide you with the details and inspiration required to light up your lake. This is a simple LED project which i'm hoping to extend to use PWM dimming with RGB lights to make any color desired.

Step 1 Putting Electricity into the water

So you want to light up your dock/boat/waterfront but you don't want to electrocute swimmers in the area. Power supplies, specifically switching power supplies can fail resulting in 110V AC zapping everything in the nearby area if any contacts or wires are exposed. Although unlikely, this could result in lawsuits and funeral expenses worth far more trouble than using a proper design.

Fortunately LEDs run on low voltage: between 2-4 VDC, this means that even with exposed wires or contacts nearby swimmers won't feel a thing. We just have to make sure we use a power supply thats failure mode wont put 110VAC in the water.

A transformer based power supply will do the trick! To the best of my knowledge these wont go 'live' upon failure. However you may need a large transformer depending on the number of LEDs used.

The best solution i've come across as a power supply (the one i used) is a 12V car/marine battery. This will ensure you will never get more than 12-14V in the water. Be careful though, if shorted these can produce very high current. Disconnect from circuit to charge.

Materials listed in this step:
12V car / marine battery, or deep cycle if possible

Comments

[Lateral Thinker]

Go solar to charge the battery.

[wireless charger led flashlight]

why need solar to charge the battery?it be charged so sowlly by solar. do you worry about it must to be used unerwater?
now I get a new underwater led lamp,which can be wireless charged
you can be view the here : http://www.wirelesspower-ledlighting.com/

[elias.alberto]

One option is to put a common 'minus' for each RGB group and one common 'plus' for each rgb color. You will use the common minus to select one given group of leds, and the common R, G and B plus will drive them the voltage they need to power up. You'll be simultaneously driving 'plus' to all other leds, but they won't work because they won't have the 'minus'. Then you cycle very quickly through all the arrays to select each array, and while a given array is selected you use pwm (or voltage regulation) on it to choose your color. This is the best method because you'll only need one wire for each color (R, G and B) and one wire for each array (six arrays) so you end up using just nine wires. And for each array you add, you'll only need one more wire (the common minus). The obvious disadvantage is you're not gonna be able to drive them full power, the maximum power of each array will be 1/n of their nominal power, where n is the number of arrays being used. But you said your leds are already being underdriven, so this is not a problem to you, thus this remains to be the best method. This is the only problem of this method, but even this problem has a very simple solution, you'll just need to put a capacitor in parallel with each led (then the problem will be the price of so many capacitors, but a capacitor will be just a fraction of the cost of each high-power led, so this is not a problem for you). The quicker you cycle through the arrays, the smaller (and cheaper) the capacitor you'll have to use. I made a drawing for you. http://img827.imageshack.us/img827/1572/instructablespowerledun.jpg :)

[Waterfox51]

Very nice. Getting the PWM going is my fall project. I think I will try and implement your method here. Thanks!

[jackyboy256]

this will go mad with my fishing kayak the light should atract the fish(correct me if im wrong) thanks man

[ElectricalFreak]

How is the capacitor connected in this circuit, and how important is it for the functionality?

[Waterfox51]

 It goes across the input terminal and the ground. It is there to ensure that only DC is getting to the circuit. Its not too important, just sort of standard practice for DC power supplies. 

[ElectricalFreak]

That is quite correct, now that i think of it the capacitor on the input terminal to ground smoothens the ripple that might occur from the supply (unless it is VERY stable).

Furthermore there could also be a capacitor on the output as a buffer.

[Nyxius]

You obviously put a lot of effort into designing and building your lights.  However, if you fail to properly insulate your circuit from the water in the lake you will have massive corrosion resulting from just a few weeks* of running.  I would highly recommend putting your lights in some form of watertight enclosure or you could risk losing your entire investment.

*Depending on the impurities in the water.

[Waterfox51]

That is exactly what I discovered when i took them out of the water this fall! I was expecting a little bit of corrosion but given that I used non-stainless screws to put them in the dock the heat sinks were covered in rust and algea. The clear lenses on the LEDs themselves had also become soft. Everything still works fine but in the sping im definitely putting them back in with a casing around them and hopefully I'll never have to take them out of the water again.

[Widespread Panic]

I have been working on underwater lights using Luxeon stars. I found they fit nicely in 1/2" PVC slip fittings. I actually have a few that I have been testing. Luxeon 7007 Endor star and LM 350 driver fitted in a 1/2" slip X 1/2" male threaded PVC fitting then potted with clear epoxy. They work well in the water but will melt down in about 10 minutes in the air. With the PVC you can come up with all sorts of mounting options. 1/2" pipe, 90 on the end, LED screwed into the 90, wires in the PVC, I ran a pair of these for 12 hours at 3 ft deep on a rechargable drill battery.

[mathews]

When you PWM your lights, have a look at the manufacturer's datasheet for the peak pulse current, as you should be able to use this to make your LEDs more efficient. If you do pay attention to the duty cycle.

Also, as you said you wanted to control the colours, as well as brightness, this could be achieved by using a small PIC, or some clever logic, to decipher a serial signal from your control panel and the LEDs. This would only require two power wires and a control wire.

And if you want to put these control electronics near to the water, look for some IP67 enclosures. IP67 means it will be waterproof upto 1m, however if you know it will not be enveloped by water, then IP65 should do.