TOPIC: Saberforge 12W LED question- Cree XB-D

Hello, all!

Apologies in advance for the long post...I like to be thorough .

I'm doing some saber work for friends, who have bought empty SF hilts and want to install NEC soundboards in them. Since NEC boards have more than one LED drive channel, it raises some questions when using SF LEDs.

According to the Saberforge website, 12W+ LEDs use Cree XB-D die.

The copper MCPCB has 2 common anodes(positive) and 4 cathodes(negative). In this case, lets assume we are working with a hypothetical led star that has 4 XB-D die, like most of SF's 12W+ LEDs do.

According to Cree's datasheets, each individual XB-D die can handle 1 Amp of power at maximum. Through the power of basic math, we can determine that a Saberforge LED with 4 die handle 4 Amps at maximum, with one amp to each die. Although, I cannot confirm this, because I don't have an ammeter

However.

The testing I've done indicates that each pair of cathodes, one pair on either side of the star, are also common.

So, to simplify, the stars LOOK like they have a common anode, and 4 individually adressable cathodes, while they actually have a common anode and, effectively, 2 individually adressable cathodes.

For example:



This is a SF 12W+ White LED MCPCB. As you can see, there are 2 positive pads and 4 negative pads. The 2 positive pads are common, which makes sense. However, the 2 negatives on the left side of the star are common, as are the 2 negatives on the right side. This does not make sense, at least not to me. I would expect them to be all separate. To be specific, I cannot provide power to the top-left die without also providing power to the bottom-left.

So, my questions (finally ) are this;

1) The LED drive channel on SF's Crimson/Viridian board pushes what current?
2) Are the common cathodes caused by something that Saberforge has done to the star?
2a) If so, why?

Thanks for sticking with me through this long post!
I look forward to hearing from you all!
F1R3ST0RM

Actually, I think they were XB-D before the update of their entire line to the 12w+, which are XP-E. However, I was not absolutely sure my recollection was correct, so I verified it with Tom Scott. I think we can take that as a reliable source. He also said he would look into updating the information on the main website.

I believe they are actually XQ-E

As for how the stars are driven, it depends on how you specify the LED order from SF. You can get individually addressable LEDs if you specify that in the order options. Otherwise I believe the default will be two channels.

When it comes to the NEC boards you have lots of options depending on the board. A common build is to do two LEDs on one channel and another two on a second channel allowing you to color mix the two channels and provide all sorts of blade effects. Spark2 is a perfect match for most SF LED builds unless you want to get into more RGB or RGB+ (or other three or 4 LED options) mixing then you could step up to the SC2 or igniter boards.

I asked Tom about that specifically, he said that the initial switch to the "12w+" did use XQ-Es, but they found that they ran a little too hot, and had to use resistors with them. Rather than continue to do that, they switched to XP-Es awhile back.

Brax wrote:
Rather than switch LEDs they could fix the heat dissipation issue pretty easily.

1st they need to stop powder coating the heatsink, or at least the base. It's inhibiting thermal conductivity between the star and the heatsink. Ideally the star and the heat sink base should be lapped, but at the very least flat, and metal to metal.
2nd they should use a good thermal interface material. Using the same type of compounds used in computer and electronics would be ideal. I use arctic silver.
3rd they should consider modifying the heatsink. Aluminum is a good thermal conductor, but has very little thermal capacity. Increasing the mass of the base of the heatsink or moving to a copper base would help.

To add:

The contact between the heatsink and the inside of the hilt is also a problem. There isn't full contact between the heatsink and the hilt. The surface area making contact is very small in many cases. Hilts that have a stop or rest that the sink sits on will get better thermal conductivity into the hilt. So the added benefit of the mass of the hilt is severely handicapped by the small surface area with which thermal transfer can take place.

I would recommend SF stop powder coating the internal part of the hilt. Again, this just hinders thermal conductivity. And you could also look at using a TIM between the heatsink And the hilt. This should.inxrease surface area contact and drastically help with heat dissipation.

And in case anyone was wondering, I used to build extreme cooling solutions for overclocking computers. Everything from air, to liquid, to LN2 systems so I've been around the block so to speak when it comes to squeezing every little bit of heat out of a system.

To the OP:

1) SaberCore boards don't have constant-current drivers, so they don't really *push* current, but just allow it to pass. There's some variable resistance in the flicker settings, but otherwise you're relying on resistors on the LED to limit current to ~1A. Board components have a limit of ~12A, I think, so you should be safe with any single star, double staff, or crossguard combo.

2) The stars come in two configurations, the two-channel X2 and the four-channel X4. Personal experience is that pre-mixed LEDs for standard single-color blades tend to be on X2 stars, while color-mixing and custom LEDs are built on X4 stars.

2a) No official response, but I imagine for Warrior and Champion setups, the X2s are easier to wire in a mass-production setup.

---

For the rest of this thread, I'll inspect the star I just got in, but I have my doubts about the LEDs moving to XP-E. The XP package is larger than the XQ-Es, and they wouldn't pack as tightly in the center as an XQ-E. I won't flat-out say that Brax's information is wrong without inspecting first though.

As for the heatsinks and hilts, there's no powdercoating going on on stock components. They're anodized and dyed, sure, but that shouldn't affect thermal transfer *too* much. Also, the modules I've received have had the anodizing sanded off on the part of the heatsink making contact with the star. I can't remember if thermal paste was installed on the modules I've worked with, since I always add/replace with my own anyway.

For the record, it is not my information per se. I asked the manager of the Customs shop, and passed on his response. So, if the star you have does not reflect the information he has, I will pass it on up to him, because he will be making changes to the verbiage on the main website based on his current assertions. So, if they are somehow in error, I am sure he would want to know that so he can post the correct information.

The heatsinks I have from SF were coated, inside and out. I sanded them down to strip off the coating. That will have an impact on the thermal conductivity if left on. To be fair, I'm also very anal when it comes to cooling.

The heatsinks are coated, perhaps, but it's not powder coat. There's no plastic/epoxy layer insulating the heatsink. It's anodizing - a thicker-than-normal aluminum oxide layer that still has decent thermal transfer properties. You can find CPU coolers with black fins because the aluminum radiator's been similarly anodized. You can go ahead and sand it down, but the raw aluminum surface will near-instantly re-oxidize anyway, just without the dye.

Sanding's still useful for providing a smoother mating surface for a marginal improvement in heat transfer, but until we start installing fans inside of hilts, I'm not going to concern myself with maximizing heat transfer since the heatsink's going to be saturated in a few minutes without anywhere for the heat to go but the rest of the hilt.

And Brax, sorry, didn't mean to imply you're coming up with your own info - I understand you're doing your best to act as middle-man to transfer info between SF and the forums. Still, when an XP-E takes up more space than four XQ-Es put together, I think you can understand my skepticism.

Great diagram on the LED sizes Kouri.

As for the heatsinks, my cooling OCd still make me cringe when I see a coated surface that's meant to be mated to another surface. I think what I'd like to see is a thermal dissipation rating on the SF heatink with passive air.

I know the LEDSupply dynamic heat sink is rated at 3W, and that has a greater mass than the SF heat sink, and both are all aluminum. I was unable to find any specs on the TCSS sinks, they use a copper base however and should have a higher thermal rating for the same size due to the increase in mass and coppers thermal properties in passive cooling.

I know we've gone aback nd forth a bit on this, with the argument of the heat sink contacting the hilt and in turn using the hilt body to conduct heat as well. And I would agree that with good contact with enough surface area then there's plenty of thermal dissipation. I have yet to see good contact on the side walls of the hilts though. My general argument is that the SF heat sink could be better.

Kouri wrote:
I remember last Winter when I thought SF was going to use the XP-E LEDs for 12W+; around that time the thing I had overlooked was the footprint. Once that was clarified I realized they would be impractical for the lens SF uses. However, a smaller LED (the old XB-D was 2.45x2.45 and the XQ-E is 1.6x1.6) would only look better under the one-up optics, so the XQ became what I thought to be the definitive LED for the 12W+.

I would take measurements, but I haven't received a new 12W+ module in a couple months (hurray bills!) so they may be from the period before the transition Tom brought up.

Latest response from Tom on the XP-E vs. XQ-E:

So, it would appear that both types are in use (depending on color), but there are no XB-Ds being used in current models.

Sorry for the necro but Googling a question got me here; seems to be better than making a new thread.

Just to confirm: XB-Ds are in fact no longer being used?

I noticed the descriptions on Etsy still say XB-D... after I placed an order for two LEDs (Deep Red and Indigo).