First LED Dive Light Build

[Dakine83]

Hi all, been lurking here for a bit but I'm hoping to start ordering parts and uploading photographic results shortly. I have two builds I'm looking at attempting soon - one dive light camera mount for my shiny new GoPro, and a MagLite Mod. To keep my parts list simple, I was hoping to buy mostly the same parts for each of these projects.

To keep this post simple, I'm going to stick to the questions I have regarding the Go Pro lights.

I'm planning a U shaped mount with the camera at the bottom center, and a dive light on each top corner and one directly underneath the middle of the mount. I will probably make this out of PVC at first, though I have my eyes on some aluminum pieces for a second try.

I found these emitters and thought they might work well - CREE XML 1000 Lumen

Questions

1. Is 3k Lumen way over kill for a video camera dive light?
2. How do I determine the necessary battery specs for a given LED / set of LEDs? I'd like about 2-2 1/2 hours run time.
   1. I was thinking I could run up to 16 AAs in a canister as the bottom of the U (about 10 inches long, 4x4 arrangement). I read AAs have more power per volume than larger cells.
3. What does one consider when selecting drivers?
4. How do you handle heat sinks in a PVC construction?

Thanks!
- Chris

 

[DIWdiver]

Hi Chris,

Welcome to the forum!

I'll get right into it:
1. No, 3K lumens isn't way overkill. It isn't even overkill. If you peruse the forums, you'll see 8K lights, and that isn't considered overkill.


2. You compare watt-hours in your light to watt-hours in the batteries times driver efficiency. The latter needs to be greater than the former. For example, you have 3x XM-L, that's around 3x10W = 30 W in your lamp. If you want this run for 2.5 hours, this means you need 30 x 2.5 = 75 Watt-Hours of energy input. Assuming you have about 90% driver efficiency, you need 75/0.9 = 83 W-Hours in your battery

 

[Dakine83]

Thanks DIWdiver!

I don't think I can hit 83Wh with double AAs in any sort of cost or space effective arrangement. In reality, these aren't dive lights, and would only be on while filming. I think I could be happy with an hour run time. If I use 18650s with 2.6Wh, I would need ~12 batteries to hit an hour run time. I'm not set on that form factor either, I just read up on some LiIon D-cells that might fit the bill.

 

[DIWdiver]

If you used 18650s with 2.6Wh, you'd be using the worst cells on the planet. They are probably 2.6Ah. Since W=A*V, 2.6Ah gives about 2.6Ah*3.7V = 9.6Wh per cell. If you get good quality ones, you'll get around the rated capacity. If you use cheapos, they are often considerably less than their ratings.

As far as capacity/cost, 18650 are probably the best, as they are produced in the highest volumes. That's why AAs are best in primary cells and NiMH.

16 AA NiMH cells would give you about 1.2V * 2.7Ah * 16 = 51.8Wh. That should get you well past an hour.

 

[Dakine83]

I found this battery and I think it could work quite well, though I would have to rethink my canister shape. Or if I want to get crazy there's this one. I'm using the calculator here and getting rough run times of 1.167 hours with the first battery and 3.1 hours with the second. Bonus benefit of each battery is they give me the right voltage off the bat.

 

[Dakine83]

If you used 18650s with 2.6Wh, you'd be using the worst cells on the planet. They are probably 2.6Ah. Since W=A*V, 2.6Ah gives about 2.6Ah*3.7V = 9.6Wh per cell. If you get good quality ones, you'll get around the rated capacity. If you use cheapos, they are often considerably less than their ratings.

As far as capacity/cost, 18650 are probably the best, as they are produced in the highest volumes. That's why AAs are best in primary cells and NiMH.

16 AA NiMH cells would give you about 1.2V * 2.7Ah * 16 = 51.8Wh. That should get you well past an hour.

Sorry DIWdiver I didn't see that you replied before I looked. Glad to see I miscalculated the 18650, that makes them much more suitable. I will check that out shortly!

 

[Dakine83]

I found UltraFire 3000mAh 3.7v batteries for a very reasonable rate. If I create a battery pack with 12-16 of these, would I need to charge the batteries individually, or could I charge the whole pack somehow? If I need to charge individually I'll just purchase a Pila and be done with it. That seems the route to go from what I've read.

Looking at these drivers too.

Hopefully I'll place an order for 16 batteries, 5 LEDs, and 8 drivers tomorrow. Whoo, exciting.

 

[DIWdiver]

Careful, those are cheapos. Probably 2200-2500, not 3000.

The drivers are pretty iffy too, but you get 4, so if even one works, it's a deal.

 

[Dakine83]

Wow, this is unbelievable - DX.com is requesting a copy of my drivers license and my credit card before processing my order. What a crock. Pretty disappointing because a lot of the threads on this site mention specific items on DX I was looking forward to purchasing.

I "chatted" with their customer service rep, who did not speak English and basically wasted my time. Very frustrating.

Anyhow, as far as the cheap batteries go - If they have 2200 I'll be happy with them. That should still get me plenty of run time. Are the drivers really that cheap? They seemed reasonably priced given that other drivers I saw all had multiple modes and weren't TOO much more...

 

[DIWdiver]

Wow, that's pretty radical, asking for a driver's license. I ordered some lenses from them a while back, didn't have to do that.

I haven't bought electronics from DX, but I've read about and looked at a lot of it, and I've used, examined, torn down and repaired similar stuff from other vendors. From what I gather it's kind of a crap shoot. Some people have good luck, some don't. Some buy extras, just in case. The simpler stuff, like AMC7135 boards, tend to fare pretty well. As with any really cheap electronics, even the best of it is only marginally well designed or built. For the price it's hard to argue with, but I wouldn't bet a dive on it, at least not without thoroughly inspecting, testing, and burning it in.

 

[Dakine83]

Well, they lost a customer. I found equivalent/same products on my favorite online retailer, Amazon. Unfortunately they're slightly more expensive, but I won't get my identity stolen either.

LEDs and Batteries are the same, I'm not sure about the drivers though. I also added a JETBEAM Intellicharger V3. The first version got some bad reviews on CPF, but the 3rd generation seems to have received a warmer welcome. I'll try this one out and if I have issues I'll spring for a better one.

Are there any recommended threads/sites for figuring out how best to match a driver with an LED, what options are available, and how to use them? For example, I just want off/on, can I achieve that with multimode drivers?

As for quality of the parts, at this point I guess I'm approaching it as an experiment. These lights aren't something I'll be depending my life on, just some footage (Currently my newly dive certified girlfriend refuses to night dive! So I have time to figure this out) If this goes well, then I'll start looking into some more long-lasting solutions. I am excited to play around with various lighting options for underwater filming, and if I can DIY it it'll be way cheaper than buying the various lights.

Thanks!
- Chris

 

[Dakine83]

Quick update on DX.com for those that are interested - They ended up charging my card without my ever giving them the "authorization" photos of my ID and CC. I immediately contacted their customer service again (ugh) and they told me in order to get a refund, I would have to verify my account by sending them the photos... are you KIDDING ME. A day later they refunded me anyhow - then two days after that they charged me AGAIN. What a cluster. I'm currently contesting the charge with Visa and have filed PCI Compliance complaints against them.

Anyhow, I'm still waiting for my LED parts to arrive, but they did land in Honolulu today so it should be soon. I also ordered myself a nice soldering station. Excited to get to work!

 

[Dakine83]

I finally got everything in and got to play around with the equipment some.

I'm really impressed with the soldering station I got, it's an Aoyue Int 937+. The thing gets up to 200c in under 30 seconds, and does a pretty good job maintaining the temperature.

I ran the LED in the picture above directly of an 18650, and man is it bright. I ran it for about 2-3 seconds to see how bright it was, and was pretty impressed with how hot it got. Is that normal, or is it the result of me running it without the driver? Google says the operating temp for the LED is 85c, or 185f... that's hot either way I suppose.

Anyhow, hopefully I'll have more to show after this weekend.

 

[DIWdiver]

Running an XML directly off an 18650 can severely overdrive it depending on the quality and charge state of the battery, and how well you connect it. I've been reading about people overdriving them to 5A with good heatsinking. But even at the 'nominal' maximum of 3A, it will get sizzling hot (literally) pretty quickly without a heatsink. I wouldn't recommend running it with no heatsink more than a few seconds at a time, as you'll pretty quickly degrade or destroy it. If it's sizzling hot, you're damaging the LED.

 

[Dakine83]

Yeah, that's what I figured. Had to try it though, plus I ordered more than I need.

I found some threads on wiring up the driver with the LED, and now I'm really confused.

Here's a pic of the drivers I bought, front and back:

I don't see any way to wire these up other than in series with the LED. Is this a different style driver? For reference, here's the link I bought them from.

Thanks!
Chris

 

[jspeybro]

The red wire goes to the + of the LED, the black wire goes to the - of the LED.
for the connection to the battery, the center pad of the back side should connect to the + of the battery, while the outer ring should connect to the - of the battery.
You can just solder some wires to these pads.

The schematics from user 'Download' are not applicable to this driver since those drivers are AMC7135 based and are linear regulators.

note that this driver only accepts the input voltage of a single Li-ion battery, so if you want to use more than 1 battery to increase the life time of the lamp, you'll need to connect the batteries in parallel with eachother and connect the common + and - to the driver.
Also, this driver will not run the XML at full power, only a few 100 lumens.
If this is not what you want, I suggest looking at this page to find a driver matching your needs:
http://www.videofoundry.co.nz/ianman/laboratory/research/driverlist.php

If you want to use multiple LEDs, you'll need 1 driver per LED, and connect all the drivers to the batteries (1SxP). I don't know if this driver supports putting multiple in series so you can connect it to 2S or 3S pack. Since this looks like a fairly simple driver, it may very well just work.


Johan

 

[Dakine83]

Wow. Thanks for all the info. I have a few questions (Bear with me, I'm still trying to figure the electrical stuff out) -

1) How did you determine that the driver would not run the LED at full power? I thought the XM-L Could accept 3.5v in, the batteries I am using run at 3.7v, and I understand there's some loss as the current passes through the driver, but is it really so much as to knock it down to just a few hundred lumen? (I just did some quick math, if the driver is 80% efficient, the voltage hitting the LED would only be ~2.96v, which is obviously on the small side of the input voltage for the XM-L... Is this how you figured that?)

2) What does 1SxP mean? 2S and 3S?

Thanks for the info. I think I'll try to wire one up, and return the rest and find a more suitable driver. Or maybe I'll just build some myself. Gotta learn this stuff some how, might as well get my hands dirty...

 

[Dakine83]

Side note! I'm proud to display my first flashlight. Wahoo!

 

[jspeybro]

congrats, I just hope you didn't just use the wood as a heatsink. Put it on a decent piece of metal! The thin contact wires in the LED can't stand the heat for more than a few seconds, although it may survive a bit longer at only 1.2A.

Let's take the specifications of that driver, taken from the link you provided:

• 1 x Cree 3W regulated power output
• Output current: 1.5V 600¡À50mA; 4.2V 1.2A
• 16.7mm diameter base, 5.6mm overall depth
• Voltage: 1.5V-4.2V
• Fully regulated circuit design

Your LED is a LED with 3.5V forward voltage and can handle 3A. If you multiply this, you get the power of the LED=> 10.5W.
The first line indicates that this is for a 3W LED.
The second line sais that at 1.5V battery voltage, the current to the LED will only be about 600mA (not sure what the funny charachters mean...). At a fully charged battery of 4.2V, it can deliver it's full power of 1.2A.

In the datasheet, you can find the forward voltage that the led will have at a certain current. At 1.2A, it is lower than 3.5V, but let's assume it stays 3.5V, your 10.5W LED will only be a 3.5V x 1.2A = 4.2W LED, which is below half of it's potential (although power versus output is not exactly linear). You could also just look at the fact that it only provides 1.2A instead of the 3A that you want.
Still, if you look at a led at 1A, it is too bright to look at, and I don't recommand doing that.

The third line is just dimentions, fourth is input voltage range and last line is just saying that it is regulating 'something', but it doesn't say what. I assume it is at least trying to regulate the current, but that doesn't seem to work below a certain voltage (probably below the forward voltage of the LED).

 

[Dakine83]

Hmm... Looks like there's not many drivers available for these then. I found a few on that link you sent but they'd been discontinued/no longer found. LEDSupply.com says they don't carry any drivers with that capacity. Or I'm just searching wrong.

No heat sink, it was more of a joke/ease of testing thing than anything. I was tired of testing by holding it by the wires so I just mounted it to a piece of wood to make it easier on me. I'm heading to a local electronics store to poke around for parts/heat sinks then to Home Depot.

Thanks for all the information, again!