[1900k edition is in!] WTS: 1900k-5800k 5mm LED 95+ CRI

[Unheard]

@Barkuti

I hope you meant to say “10 in parallel to an AMC7135”.

I’ve read that’s not a good idea, but then I have not much clue about those things. I guess parallel is easier for the lower voltage needed?

Need to read about MOSFET circuits :weary: .

[Jerommel]

@rngwn

You can PM me and choose the shipping option you desire (Pricing & fees in the OP).

If you want to make things easier for me, you can summarize the pricing in the PM for me.

(Tracked shipping is kinda pointless for Netherlands though, since it can’t really be tracked)

Ordered and paid. :+1:

[Jerommel]

@Unheard

@Barkuti

I hope you meant to say “10 in parallel to an AMC7135”.

I’ve read that’s not a good idea, but then I have not much clue about those things. I guess parallel is easier for the lower voltage needed?

Need to read about MOSFET circuits :weary: .

No, that’s fine.
For 10 in series you need 32 29 Volts.
For 10 in parallel you only need 3.2 2.9 Volts, like from a single Li-Ion cell.
The AMC7135 will eat up a minimum of 150 mV.

[Barkuti]

In any case, driving leds in parallel could have some current sharing problems due to Vf differences between emitters. This can be minimized by binning leds with a multimeter, i.e. set them all extended over a table in a room with stable temperature for a little while first (acclimating emitters, they're sensitive to temperature) while laying a multimeter close, then use the multimeter to read and note down every emitter's Vf systematically at least once. Use the results to sort the emitters in Vf packs: 10 lowest, next 10, …, last and highest Vf 10-pack. This would minimize the above problem.

[rngwn]

Well, as a word for caution, Vf disparity will be an issue.

The 3400k/5800k does have 0.1v higher Vf than 2300k.

[Unheard]

I will, Barkuti. Thank you guys .

Will come back with questions when the project advances, I fear

[Unheard]

@rngwn

Well, as a word for caution, Vf disparity will be an issue.

The 3400k/5800k does have 0.1v higher Vf than 2300k.

No problem. The colors will be driven seperately.

[rngwn]

Just an update:

only 5 2 packs left for 2300k.

I will check up with my supplier on Monday and see if I can restock this 2300k tint.

[Barkuti]

There are many ways to drive emitters. Arrays of series emitters will display closer average Vf sum, this for example means it would be far better to drive a 10-pack in 10S or 2P5S arrangement. Watch out I said 2P5S, this means 2 parallel 5S arrays, which is a lot different than 5S2P. There are cheap boost DC/DC converters which can output that voltage from li-ion cells easily:

• https://www.aliexpress.com/item/32946554224.html
• https://www.aliexpress.com/item/32660917982.html
• https://www.aliexpress.com/item/4000207182126.html
• https://www.aliexpress.com/item/32913985828.html

The MT3608 boost module is going to be reviewed by Henrik soon I think, sent him a 5 piece pack long ago. Now that I recall this, it was the 5th of August, he should have received the package sometime in September and we're almost in December already.

[rngwn]

@Agro

There are very few options for CRI95+ SMD MP LEDs with reasonably priced worldwide shipping.
Actually I have found literally just one offering on Aliexpres, for 2835 LEDs. Everything else seems to have expensive shipping.

I suspect I’m missing something and I spend merely an hour or so on the search. But anyway - this is not something widely and easily available for a reasonable price.

About that CRI 95 SMD, you mean this one?

0.46€ 89% OFF|100PCS Hohe CRI 95 + 2835 SMD LED 3V 60ma 16 26lm 2600 7000K...

[Agro]

Yes

[iamlucky13]

Regarding driving LED’s in parallel, I think we can make some basic deductions from djozz’s data:

[1900k edition is in!] WTS: 1900k-5800k 5mm LED 95+ CRI

[image] I did a voltage and output test on one of these 3400K 95CRI leds, and it does not disappoint, output is better than the Yuji, voltage is lower, and it can handle more current. The max is about 22 lumen at 100mA, going higher up to 120mA gets you a bit more light for a moment but it settles back to 22 lumen again within a couple of seconds. My test rig for 5mm leds is not great, the current can not be set very well and the graph shows it, but the output numbers are correct. I also re-tes…

If you’re driving 10 at 350mA, that’s 35mA each.

From djozz’s graph, that’s about 2.95V.

If you had one LED in the group with a Vf that was lower and therefore hogging the current, then from the same data, I’d estimate the resulting current in the worst-driven LED as follows:

0.1V lower = 55mA
0.2V lower = 70mA

Since one of his survived an isolated test for 12 hours at 100mA, the over-current does not seem to be a problem. However, rngwn observed that if packed together, they heat up and may eventually run away:

[1900k edition is in!] WTS: 1900k-5800k 5mm LED 95+ CRI

I decided to make a light module out of 28 LEDs in parallel. Hooked it up to a lab bench. Without constant current regulation, any initial current above 840ma (30ma per LEDs) will result in a (very gradual) thermal runaway where the module start to pull more and more current and heat up more until it would presumably burn out. On the first try, I initially set the current at 1.4A, and it rose up to almost 1.6A within 10 minutes. Granted, these LEDs are packed fairly tightly together and thus…

So for the idea of running 10 on a 7135, I think heat is the main concern.

[Jerommel]

Yes, heat can be a problem in those 3xAAA 20 or more LED lights.
Especially those in the middle of the PCB can get hot on the crappy stock PCB they’re soldered on.
Good idea to epoxy a heat spreading disc on the back.

[Jerommel]

@iamlucky13

@Unheard

@Barkuti

Just found this 5mm led powered Mateminco BL-01 thingy @ FastTech:

Very nice little bullets. Are the LEDs up to the specs of this lights? I imagine current might be somewhat higher than 25mA. No?

They’re powered by three LR41 alkaline button cells. The 45 lumen stock rating strikes me as extremely unlikely.

Those cells can’t push much current. I don’t expect it would be any problem.

The LED that’s in those bullets is a 0.5 Watt 5mm LED similar to this:

I bought a copper bullet branded Astrolux (i think TB-01 ?) with pretty powerful 3x LR41 inside plus 3x LR41 spare batteries a few years ago from Banggood.
I estimate it’s around 15 Lumen with fresh batteries, maybe even 20 Lumen.
Pretty impressive for the size.
Those Mateminco branded ones are crazy expensive.
Here’s a stainless steel one:
https://www.aliexpress.com/item/32844630381.html
You can see the brand name is photoshopped away, but i bet it says Astrolux.
Here’s an aluminium one:
https://www.aliexpress.com/item/32839012681.html

Either way, yes it would be nice in high CRI warm white, but Djozz tried it with a Yuji 5mm LED iirc, and it was much much less bright.
These LEDs here will do a better job, but still a lot less than the stock LED.

I think these LEDs are better suited for lights like this:
https://www.aliexpress.com/item/32885217288.html
https://www.aliexpress.com/item/33023962121.html
https://www.aliexpress.com/item/32923872041.html
https://www.aliexpress.com/item/4000385078691.html
https://www.aliexpress.com/item/32775843914.html

[Jerommel]

[DBSAR]

PM sent! i am interested in a pack of the 2300K and a pack of the 3400K for mini lantern mods & builds.

[rngwn]

And with that, the 2300k is out (except one reserved for Skylight)

Will let you know if the supplier got any left.

[rngwn]

New list of T/Ns

iamlucky13 - (1x 2300k / 1x 3400k)
candor - (1x 2300k / 1x 5800k)
Agro - (2x 2300k)
nastynate - (1x 2300k)
Jerommel - (1x 2300k / 1x 3400k)
DBSAR - (1x 2300k / 1x 3400k)

Asian8640 - (1x 2300k / 1x 3400k)
mitsuki08 - (1x 2300k / 1x 5800k)
nismo - (2x 2300k)

Djozz - ()
skinny_tie - (1x 2300k / 1x 3400k / 1x 5800k)
nismo - (1x 3400k, 1x 5800k)

Scientist - (1x 2300k)
Buck91 - (1x 3400k)
DBSAR - (4x 3400k / 2x 2300k)
datiLED - (1x 3400k / 1x 5800k)

u/somnambulism (1x 2300k / 1x 3400k / 1x 5800k)
Skylight - (1x 2300k / 2x 3400k / 1x 5800k)
Slayer1 - (1x 2300k)

[Agro]

@iamlucky13

Regarding driving LED’s in parallel, I think we can make some basic deductions from djozz’s data:
[1900k edition is in!] WTS: 1900k-5800k 5mm LED 95+ CRI - #109 by djozz

If you’re driving 10 at 350mA, that’s 35mA each.

From djozz’s graph, that’s about 2.95V.

If you had one LED in the group with a Vf that was lower and therefore hogging the current, then from the same data, I’d estimate the resulting current in the worst-driven LED as follows:

0.1V lower = 55mA
0.2V lower = 70mA

Since one of his survived an isolated test for 12 hours at 100mA, the over-current does not seem to be a problem. However, rngwn observed that if packed together, they heat up and may eventually run away:
[1900k edition is in!] WTS: 1900k-5800k 5mm LED 95+ CRI - #171 by rngwn

So for the idea of running 10 on a 7135, I think heat is the main concern.

Note that the LED with the lowest Vf will get hotter than the others. Which will lower its Vf further.
I don’t know if this is the case here but sometimes it spirals out of control.

[Nismo]

So I did some more replacing of LEDs, this time in my new Sangean MMR-88 DAB emergency radio. The original LEDs were 3mm 6500K ones, changed them out for the 5mm 2300K LEDs. Had to drill up the reflector but that was pretty easy as it was just plastic. The PCB for the lights were modular and unpluggable, so the job was pretty easy. Overall I think it turned out well, brightness isn’t the greatest obviously, but it was pretty terrible with the original LEDs so it didn’t matter much.

Beam profile and color temperature of the new LEDs, camera @5000K

Unfortunately I don’t have a picture of the old beam profile, but here’s one of the original LEDs. Camera @5000K

The light itself on low brightness. It has four modes; high, low, flashing and SOS. When the radio is off, it’s just high and off unfortunately. Should’ve been low, high and SOS.

Time to change all 5mm LEDs I can find!