Led4power.com : LD-4 CC linear drivers, ILC-0/1 illuminated tailcaps, optics, MOSX, copper DTP MCPCBs...

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To find out resistance of spring that I have for sale HERE

I used rigol DP811 in CC mode at 1,2 and 3 A and measure voltage drop with 4-wire method.

Djozz did similar test for few springs quite long ago: https://budgetlightforum.com/t/-/29825

I measured resistance for 3 other springs to check consistency: convoy steel spring, fasttech bronze spring, Intl-outdoor beryllium short spring.

Results are:

Convoy steel spring:

1A 43,5mV :R=43,5mOhm

2A 86,4mV : R=43,2mOhm

3A 133mV : R=44,3mOhm

Avg. resistance: ~43.7mOhm

Fasttech bronze spring:

1A 22,5mV :R=22,5mOhm

2A 44,8mV : R=22,4mOhm

3A 67,2mV : R=22,4mOhm

Avg. resistance: ~22.4mOhm

Intl-outdoor beryllium short spring:

1A 7,4mV :R=7,4mOhm

2A 14,63mV : R=7,32mOhm

3A 22,5mV : R=7,5mOhm

Avg. resistance: ~7.4mOhm

Phosphor bronze spring 12x9x1mm

1A 13,4mV :R=13,4mOhm

2A 26,82mV : R=13,4mOhm

3A 40,5mV : R=13,5mOhm

Avg. resistance: ~13.4mOhm

It's obvious that measurements are very consistent and independent of current.

At higher currents resistance of steel spring starts to increase due to temperature rise caused by power dissipation.

Intl.outdoor spring has smallest resistance, but it's also the shortest,and not very "springy".

Conclusion is that 12x9x1mm bronze spring is good for currents up to 6-7Amps without need for bypass, which should be perfect for medium (by today's standards) lights, or for SRK-like mulitcell lights.

Spring is big enough to add bypass of course, good thing compared to bypassed steel springs is in case of bypass failure spring has still very decent conductivity and probably won't melt,unlike steel springs.

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^ :sunglasses:

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Thanks for the testing led4power. :+1:

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Very nice, thanks for testing!

I have to say, you’re doing an amazing job offering specialty products which precisely cater to the unique needs of modders on the flashlight forums! You fit in perfectly with some of the other guys like Clemence and Lexel (and maybe the Sandwhich Shoppe 10-15 years ago). Everybody has their own niche where they offer their unique products. You seem to be especially motivated though to offer stuff that has never existed before and is very practical. And all of that for such nice prices from a guy who knows what he is talking about. :wink:

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Finally first LD-B4HV test (Luxeon M 6V version as test LED on 20mm 4040 mosX, 6A LD-B4HV):

6A high mode, top side of mosfet is still cold:

Two 6V Luxeon Ms in series as simulation for 12V (4S) LEDs like XHP-35:

6A high mode, 16.4V input, around 100Watts input/output power:

I will try XHP50.2 in Convoy C8 host with LD-B4HV and 2x18350 Aspire cells soon.

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Have I missed something or is this your new 2S/3S driver? Side switch capable?

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Yes, this is 1S-4S variant of LD-B4 (1S only). Side switch will be available later, it's supports clicky switch for now.

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It is capable of driving a 3v led with 1s, 2s, 3s and even a 4s battery setup? Without needing to change components on the driver?

Or is 1s still limited to 3v LEDs and 2s to 6v leds and 4s to 12v LEDs?

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It can drive 3V LED with any voltage up to 20V, but this is linear driver,it burns extra voltage into heat. This driver is good when voltage of LED and battery are similar, like 2S cells and XHP50.2, XHP70.2.

In combination with mosX MCPCB generated heat in mosfet is not problem at all,since it's well cooled on mosX. Second generation of XHP50 and XHP70 have very low forward voltage, so they draw too much current with DD drivers which can lead to LED death or at least low efficiency because of too high current. Efficiency is equally bad in all modes that are derived by PWM of DD mode. Also 7135 regulators have max. operating voltage lower than 8.4V, so reliability is questionable when they are used in 2S setups.

This drivers provides constant current on all modes, so there is no problem with too much current on high mode, LED efficiency is max. possible in all modes. Disadvantage of CC method was extra heat generated in driver(mosfet to be precise) - that is completely solved with mosX board because mosfet is on same MCPCB as LED.

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Are you planning someday to develop a buck driver, to run leds from a battery set-up with much overvoltage, like 2S for a 3V led?

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Yes, but I have to have linear drivers too, they will always be one of the options because of small size and relatively low cost/Watt.

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Do you have exact specifications for the thermal conductivity or thermal resistance of the insulating layer of the MosX PCBs?

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I filled my Jaxman M8 with Led4power’s components, led driver mcpcb tailswitch and springs too. link to pics . By now most of my collection has at least something from this store inside, a good testament to how much I like the stuff but I’m going to have to try to do something different in my next build not to let things get too boring :smiley: .

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I know dielectric thickness is 35um,dielectric conductivity is not specified directly, but based on some other numbers I calculated that it must be around 10W/mK.

So it should be equivalent to ~160um of PbSn solder layer thickness (I calculated this before as 200 something um,but that calculation was wrong).

Most of DTP boards have that order of magnitude DTP pad height variation, so performance in theory should be DTP-like for most LEDs, to check this I will do some DTP vs mosX tests for several LEDs.

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Thanks. The central solder pad of the Osram Black Flat has an area of 3.06mm2.

So the thermal resistance of the insulating layer when using this LED is: 35μm / (10W/m*K * 3,06mm2) = 1,144°C/W

Add this to the 0.027°C/W of the aluminium PCB (1.6mm thick, 210W/mK) you get 1.171°C/W.

With 22W (maximum measured by Köf3, can vary quite a bit, I assume 80% efficiency) it thus adds ~20.6°C to the temperature of the LED.

Assuming perfectly even solder pad height a 20mm copper Sinkpad PCB would add less than 1°C (0,0147°C/W).

So while you're PCBs are a great idea, I agree with you in not reccomending them specifically for the Black Flat (most people use this LED at close to maximum power). Does your supplier offer other insulation materials?

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I will test black flat also. Your calculations are correct, at extreme power densities even solder thickness and DTP pad flatness has great influence.

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First test: XM-L2 (U4 bin probably) on DTP vs mosX

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^ looks like the same performance.

Was it the same led reflowed first on the DTP board and then on the mosX board? What happened at ‘FAIL’ ?

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POOF! :smiley:

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Two different LEDs from same tape, at 6A they died, I think this was known characteristic of XM-L2 U4 bin,besides extremely high Vf.