Finished: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

[Techjunkie]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

I did some rough estimate math and calculated that if the cells are dropping to 1.05 Vout under load (guessing at this figure based on what Eneloop AAs and Titanium PowerMax 1800 AAs drop to under 10A load ), that's 4.2V. Each emitter needs only ~3.3V to reach the target max current. That means to maintain max output, the regulators need to drop .9V @ 12A, and shed 10.8Watts of heat. I realize now that's asking a bit too much considering the heatsinking available to them in this space.

I've just ordered some 5W 0.15 ohm cement resistors. Two placed in parallel in the tailcap will equal one 10W 0.075 ohm resistor. Using the math above, that should drop the voltage on the pack 0.9V @ 12A and land the target voltage right where it needs to be, leaving the regulators with little to no work to do.

12A = .9V/0.075ohm
0.075ohm = .9V/12A

I'll have to heatsink the resistors in the tailcap as best I can, considering that they'll be run slightly over spec when the batteries are fully charged and the light is on high.

Before arriving at this (latest) conclusion, I had already desoldered the regulators, from when I was planning to replace them with the older versions. While I'm waiting for the resistors to arrive, I'll see if I can solder all four into a short section of copper tube, which should improve their heatsinking somewhat.

Wish me luck.

*EDIT* I think I can fit 3 x 0.22 ohm 5W resistors in parallel in the tailcap. At 12A current, they'll collectively drop voltage 0.88v, leaving the regulators very little work to do. Each resistor will run at 3.5W, which will be in spec for them. Each regulator will have to burn off 0.48W, or 1.44W collectively, which is waaaay cooler than the 10.8W they'd have to burn without the resistors.

 

[FRITZHID]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

IDK if its my screen or what but the SST may be smaller, but it looks brighter... maybe it's just the color temp?

 

[Techjunkie]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

IDK if its my screen or what but the SST may be smaller, but it looks brighter... maybe it's just the color temp?

I'll grant that the SST has brighter spill, but that's because the XML has almost all that spill concentrated into the giant, brighter hotspot. The ceiling bounce test says its no contest. I was shocked at how much brighter it made any room in my house compared to the fixed lighting.

On to the updates...

As I mentioned, I'm re-doing the same drivers while I wait for the resistors for the tailcap to arrive. Side note - It occurs to me that if the XML weren't so low Vf, and/or if I'd not bypassed the switch, and/or I'd used cells with more internal resistance, I probably wouldn't even need the resistors to bring the pack halfway down between 4 cells and 3 cells.

Rather than just reassemble them as they were before, Here's what I've come up with in an attempt to improve heatsinking...

Run 20awg stranded copper through the three sets of large via holes at the outer ring, and solder to both sides of every board, connecting all the boards thermally. Also solder the foundation of every AMC7135 chip to the outer ring and those wires stringing the boards together, using liberal amounts of solder:

Next, cut a piece of copper pipe, customizing diameter to fit inside heatsink base. Press new driver stack and wires in place, applying liberal amounts of HS paste between the inside of the tube and the new thermal bridges created with all that wire and solder.

Fit into place, making sure the switch will line up with the switch hole when everything is fully tightened.

I'm very happy to report that everything survived this operation. I've also noted that on high, my amp meter shows 11.6A in the forward direction, and -12.9A when wired in reverse. I see now that it's accuracy above 10A is shaky, unless I take the average of those absolute values, which is just slightly above 12A.

I'm less happy to report that installing four fully charged cells has confirmed that all this new driver heatsinking has alone not solved the problem. Here's hoping that the resistors do, or I think I'll just end up swapping the 4C tube for a 3C tube and call it a day.

 

[LilKevin715]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

The AMC7135 linear regulators are relatively cheap and flexible (somewhat), but they do have their limitations as you have found out. Have you tried the light outside yet? I am curious how much throw those optics provide.

 

[Techjunkie]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

The AMC7135 linear regulators are relatively cheap and flexible (somewhat), but they do have their limitations as you have found out. Have you tried the light outside yet? I am curious how much throw those optics provide.

I have, but I haven't taken beamshots outdoors yet. Throw is on par with my triple SST-50, but with an entirely different beam profile. The hotspot of this light is a huge rounded square that reaches as far, perhaps slightly farther, than the smaller hotspot of the SST light. These optics gather a lot of the light that would be spill in a reflector, and add it to the hotspot.

 

[CKOD]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

IDK if its my screen or what but the SST may be smaller, but it looks brighter... maybe it's just the color temp?

The image is saturated/washed out in the center. its impossible to compare the brigtness unless he stopped down the exposure or added filters

 

[netprince]

I like this build a lot. That optic is really interesting. A shame about the overheating drivers. Have you considered a different driver all together? My first instinct would have been one of the taskled drivers, directly attached to the bottom of the copper heatsink.

BTW, sorry if I missed it, but what is the sku on that optic? I might like to try it sometime...

Thanks!

 

[Techjunkie]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

The image is saturated/washed out in the center. its impossible to compare the brigtness unless he stopped down the exposure or added filters

I agree. I've charged the cells in all the lights and will take some better beamshots for comparison soon, maybe tonight.

I like this build a lot. That optic is really interesting. A shame about the overheating drivers. Have you considered a different driver all together? My first instinct would have been one of the taskled drivers, directly attached to the bottom of the copper heatsink.

BTW, sorry if I missed it, but what is the sku on that optic? I might like to try it sometime...

Thanks!

Thanks, netprince. I don't think I could fit 4 Task LED drivers into one light. (Keep in mind that pack voltage is only 4.8V, and I want each LED regulated individually at 3A, not 2x2 in parallel at 6A or 4 in parallel at 12A. That's why four are needed.) Also, I'm not sure how to do the mode-slaving on them in the same way as I'm doing on these, and cost is a concern too. DX sku for the optic is 01915.

 

[Techjunkie]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

New stopped down beamshots with batteries fully charged on all lights. Current draw shown in photo captions confirmed with talcap measurements immediately following the shoot.

 

[LilKevin715]

Re: Beamshots: Quad XML Mag 4C (Optics NiMH 3-mode) new everyman's recipe

Nice beamshots. Those optics really do provide a good amount of throw. Not to mention they are more efficient (~90%) compared to regular reflectors (~75-80%).

 

[Techjunkie]

The various 5W resistors I ordered came in the mail today. On the 2nd try, I found the right combination, 3*0.15 ohm resistors in parallel in the tailcap. Ironic that this time I would be modding a tailspring to ADD resistance, not remove it.

Here are the three resistors fitted into the cap with the edges of two beveled so they'll fit, and the ground wire in place, and a pic of the spring taped up with kapton tape to avoid it contacting the tailcap directly, thus ensuring the current goes through the resistors, not the spring.:

Here's the tailspring fully assembled:

Here's a tail measurement from cold, without the resistive tailcap in place:

Finally, here's a tail measurement through the resistive tailcap immediately after a long run on high to the point where the head was burning my hand. I held the leads to the DMM in place long enough to ensure there was no thermal rebound and that the current shown was sustainable:

Success!


Note to self: just changed driver modes from HML to LMH, hoping to eliminate flash when power off in low mode. It didn't help, but at least the mode selector was easy to reach and the mode order matches other lights now.

 

[charlestt]

Hi there i'm in the middle of building a similar light as your self but with 3xml U2 leds and three drivers and i'm having the same problems with the drivers getting very hot on full with 4 nimh c cells, i've tried it with 3 but i only get around 4amps that shoots up to around 10amps on four.

I want to try your method with the resistors but i don't have a clue how to work out the values and on top of that the only electrical shop i have access to don't sell exactly the same as what you've used. Would you be able to look at what they have and suggest to me the ones to go for?

Here's a link to the company in question. http://www.maplin.co.uk/search?criteria=resistor

I'm using a 3d Mag if that makes any difference..

Cheers

Charles

 

[Techjunkie]

Hi there i'm in the middle of building a similar light as your self but with 3xml U2 leds and three drivers and i'm having the same problems with the drivers getting very hot on full with 4 nimh c cells, i've tried it with 3 but i only get around 4amps that shoots up to around 10amps on four.

I want to try your method with the resistors but i don't have a clue how to work out the values and on top of that the only electrical shop i have access to don't sell exactly the same as what you've used. Would you be able to look at what they have and suggest to me the ones to go for?

Here's a link to the company in question. http://www.maplin.co.uk/search?criteria=resistor

I'm using a 3d Mag if that makes any difference..

Cheers

Charles

Charles,

The web store that you linked to doesn't appear to have any high power resistors of low enough R value. The ones I used came from China via eBay. Try searching eBay for "Ceramic Cement Power Resistor 5W 0.15 ohm". You can get a bag of 10 for ~$3 USD. With grinding of two edges on two of them, I was able to fit three inside a Mag C tailcap. Best of luck with your build.

 

[charlestt]

Charles,

The web store that you linked to doesn't appear to have any high power resistors of low enough R value. The ones I used came from China via eBay. Try searching eBay for "Ceramic Cement Power Resistor 5W 0.15 ohm". You can get a bag of 10 for ~$3 USD. With grinding of two edges on two of them, I was able to fit three inside a Mag C tailcap. Best of luck with your build.

Excellent thanks for your help i'll take a look..

 

[charlestt]

all i can find is these but they look deceptively big ... What do you think ?

http://www.ebay.co.uk/itm/10pcs-5-W...upplies_ET&hash=item20c4b99d88#ht_2084wt_1351

 

[Techjunkie]

Those are kinda long. I was thinking more like these.

 

[charlestt]

Those are kinda long. I was thinking more like these.

Now they look more like it i'll get a set of them ordered up.

Cheers for that

 

[charlestt]

Now they look more like it i'll get a set of them ordered up.

Cheers for that

I know what i was going to ask you, what gauge wire are you using between the primary driver and the switch ? I'm using 20 awg but it too is getting pretty hot when on full power.

 

[Techjunkie]

I know what i was going to ask you, what gauge wire are you using between the primary driver and the switch ? I'm using 20 awg but it too is getting pretty hot when on full power.

If yours is wired like mine, where the primary driver's mcu is on a parallel circuit to the LEDs, then the wire from the switch to that driver carries only a few mA. For that one, I think I'm actually using 22 awg, which is overkill. For the LEDs, each LED lead is 22 awg and the main pos wire and ground wire are 20 awg (and as short as possible).

 

[charlestt]

If yours is wired like mine, where the primary driver's mcu is on a parallel circuit to the LEDs, then the wire from the switch to that driver carries only a few mA. For that one, I think I'm actually using 22 awg, which is overkill. For the LEDs, each LED lead is 22 awg and the main pos wire and ground wire are 20 awg (and as short as possible).

Yeah i've wired mine they same way as yours, i have 22awg going to the leds and switch and 18awg going to the battery so i guess i'm using the right stuff.
Unfortunately whilst using the flashlight the cheapo glass that i got from DX cracked so now have to wait for some decent stuff to come from the US :-/