Homebuilt ROVs Forum

Hi,

I just recently tested these LED's from Bridgelux: http://www.newark.com/bridgelux/bxra-56 ... tt=73T6218

Here is a video of the testing:


They run at 21v and draw approximately 550mA.

In the video I was using a Zahn step down regulator from 48v to 21v.
In my actual ROV design, I will be using one of these to step 12v up to 21v: http://www.ebay.com/itm/111068870558?ss ... 1439.l2649

In the test the LED was bolted to a 1/2in aluminum plate, with thermal paste between the LED casing and the aluminum for good heat transfer.
In my ROV, I am going to be using a housing like the image below. I hope to have that manufactured in the next week or so.

If anyone would like more information please just ask.

Thanks,
njs552

That looks brilliant! (pun totally intended!)

So from what I can tell, that is just the LED module, and a power supply!? Are you using a LED driver anywhere?

Thanks!

It will be just be the LED and a step up power supply. No driver for now, just a SSR relay board for on off control.

I am looking a designing a PCB with some MOSFET's, and inductor, and some high power capacitors as a PWM controlled LED driver, but for now I think that on and off will do the trick.

Have you seen a good off-the-shelf driver board for DC LED's?

I see "constant current" LED drivers, but not a good controllable one yet for a good price.

Thanks,
njs552

Hey njs552,
In a word... no. I have not been able to find a good LED driver for ROV use. I did find one that looked like it would do the trick... but for some reason I have ruled it out. (Can't remember at this time why I did that...)

http://www.digikey.co.uk/scripts/dksear ... 11-d-v-700

Ryan
"KR2_Diving"

Very nice LED housings. Are you manufacturing these yourself? I have been looking fruitlessly online for off the shelf housings that I can use. I have two identical LED's for my project but to date not been able to come up with a heat sink that will do what I want. I'm using a DC to DC step up regulator to drive the LED's. Plan on potting mine (complete incapsulation) with QSIL 216. It is non electrically conductive, optically clear and a thermally conductive potting compound. That way I don't have to worry so much about sealing the housing.

@KR2_Diving, I think that it would be a simpler solution to just have them on off, and it saves space in the pressure vessel. Maybe a LED driver could be an update or in a version 2.

@bikerbones1968: I am manufacturing these myself. I have some 2.5in aluminum round bar, and I am using a lathe and a CNC to manufacture all the parts.

I am using the aluminum body as a heatsink, and thermal paste between the LED and housing. Because 99.9% of the time I turn the lights on they will be underwater, the water will conduct heat away form the aluminum far better than air. Even in air, these only got to 36C after 5min(attached to a piece of 1.2in Aluminum).

The thermal resistance of your epoxy is 0.18 W/m-K, and 6061 aluminum is 167.156 W/m-K. I am not exactly sure what that data means but if I understand it correctly from some google searches, namely here( http://computer.howstuffworks.com/heat-sink1.htm) then the higher the number the better the material is at conducting heat. You might want to consider at least some type of heat sink because that epoxy may not do the trick.

Have you tried potting a light yet in opoxy?

Thanks,
njs552

I have the specs but I think I should have explained a little better the purpose of the potting compound. I will be using an aluminum housing for the heat sink, almost exactly as the housing you are building. Problem is I do not have easy access to a lathe so manufacturing these will be the challenge. My thoughts are the same and to only operate the LED's once submerged and let the water assist in dissipating the heat. The potting compound will be basically poured on top of the LED, encapsulating it from water. This way I will not require a glass lens or an O-ring and collar and worry about having a pressure resistive enclosure.

bikerbones1968 wrote:The potting compound will be basically poured on top of the LED, encapsulating it from water. This way I will not require a glass lens or an O-ring and collar and worry about having a pressure resistive enclosure.

When you explain it like that, it sounds like a great idea! Solves a few issues all at once! The only drawback I would see with that is there would be no "repairing" the unit.

I was thinking of building a similar unit myself, but including a thermocouple. If nothing else, it is a neat feature to throw into my arduino!

I figured I paid like 15 bucks each for the LED's and a piece of 2" diameter aluminum round stock is practically free around the scrap metal places here. So I just need to make a "cup" out of the round stock and fill with the potting compound. Its a throw away design but properly cooled and protected the LED should last a very very long time.

OK. That makes sense. That design is good for a permanent LED. I believe the LED chips already have some sort of resin on top of the physical LED's, so it should work nicely.

I like the thermocouple idea. What are you using? A k-couple sensor of something like this? http://www.ebay.com/itm/10pcs-NTC-10K-2 ... 3a828ef6ab

I am using a USB cable to supply power, so maybe I can use a wire to send back a temp sensor reading.

I can hopefully swap in different LED's with my current housing design because Bridgelux makes all their LED's with the same square form factor, if a bit different dimensions.

I got a 2.5in x 6in piece of 6061 round stock for $10. Will make four housings I hope. It will probably ~$20 per housing.

Thanks,
njs552