The There Are No Stupid Questions Thread

I have found some 10mm MCPCBs that are made of copper but not DTP.

Do you think it would be a good idea to remove the insulating layer below the thermal pad until the copper is exposed and solder the led to it?

Will the solder layer be too thick if I would fill up the gap between the copper and the led thermal pad with enough solder paste?

How hard are you gonna cook the LED if it only sits on a 10mm board??

Unless you’re gonna try to push multiple amps through it, not even Al vs Cu would make that much difference, let alone Cu-dtp vs -non-dtp.

I recently ordered a protected Panasonic ncr18650ga 3500mah cell it didn’t register on my charger. so today I put it on the charger again and it registered at 1.73v which concerned me. I’ve got it up to 2.23v now, should I try to get it above 3v or not?

Let’s say 3 or 4A in a multiple led direct drive setup.

I just thought it would be some sort of DTP if you scrape away the central part of the 3535 footprint and add enough solder to get a direct connection to the copper of the board. Does that make sense?

Mmm, I see “10mm” and I’m thinking an AAA light. :laughing:

It’d work, but solder (Pb/Sn) isn’t the best of thermal conductors. Grind away too much to expose the Cu underneath, and you may have less conductivity vs leaving it alone. Plus, be sure to have an “overflow channel” so excess solder can squish out and the LED doesn’t float on the molten solder.

Someone did tests of various thermal compounds vs just squishing down (via screws) the board dry, and there was negligible difference.

Me personally, I’d leave ’em as-is. Combination of laziness and diminishing returns…

It will work well, I tested it 5 years ago. Maybe for 3535 boards the result is a bit worse than 5050 boards but I expect that the thermal path is still much improved compared to the situation with dielectric layer.

I need some advice and help determining which DC power supply to buy for flashlight modding.
Probably could get by without one but just want to learn as much as possible.
There are switch mode and linear, 30V 3A, 30V 30A.
I’m not an electronics tech but want to have more fun.
Thanks for not laughing :beer:

I like this one, but is it the correct one ?

I’m not an electronics geek myself, but have bought a few power supplies over the years for my flashlight hobby. My most used PS is a heavy lineair one but I understand that using a switched mode PS for what we do is perfectly fine. The one you linked is very cheap, so expect some imperfection, like bumpiness when finetuning the current, and spikes when switching the PS on, I expect you can blow sensitive leds with that (but not likely the power leds we are using). I think 5A max is a bit low, maybe 10A is more versatile.

djozz , Thank You for that. I will wait and keep learning before buying one. :beer:

That falls in my “recycle this carefully so as not to set the recycling truck on fire” category.

Are you sure it’s protected? Measure the length.

A protected cell will cut off power once it reaches 2.5v. That is about the lowest safe voltage you can go. Below 2.5v the cells go through chemical changes which ruins them. They become fire hazards when charging. Keep tabs on how hot it gets.

I would contact the store you bought it from. It doesn’t sound like it’s protected, plus it’s ruined.

If the drain is very low, like what happens with a lighted tail flashlight, or one with high parasitic drain (FT02!!!), the protection circuit may not be triggered and the drain continues beyond the safe voltage.

Or am I mistaken with what some flashlight drivers do and will protected cells indeed detect the correct voltage and shut off even with very low drain?

Thank you, djozz and Lightbringer for your advice regarding DTP and non-DTP MCPCBs. Nice and useful test you did there, djozz. :+1:

I think I managed to get very unlucky. It is an EVVA 10A protected cell but it was stuck in the mail for a week and it wouldn’t charge for a few days after it got here. My charger read resistance to be 999mΩ, so I think I’ll see what I can do when It comes to sending it back.

Thanks hank,JasonWW and djozz.

Is this a random question?

The low voltage protection circuitry in a battery will cut power whenever the voltage gets to it’s lower limit, like around 2.5v.

The LVP in a driver like NarsilM and Anduril will only be active when the driver is active. For instance the light is left on at a low level. When you turn off the light, the MCU goes to sleep to reduce parasitic drain and the LVP is not working. Usually the parasitic drain, even with a lighted side switch, is so low it will take years to run down the battery, depending on the light model, of course.

hi, if I put this uv glass in my regular convoy s2+ will it work as a uv light?,searchweb201602_3,searchweb201603_53

ok trying to answer my own question. if i get that glass and this bead

I already have a convoy s2+.

so I think I reflow the solder on the board. twist it out. reflow the solder on the LED. remove. then solder the bead to that board. switch out the glass. then screw it all back together and solder the board back?

seems simple enough. am I missing something?

thanks everyone.

Yes, but it won’t be very bright.

First you need to make sure your S2+ driver will not burn up that led. Ad says no more than 0.5A from driver. If you have the 8x7135 driver, you’ll need to remove all but 2 of the 7135 chips. 0.7A is probably okay.

It’s better to buy the led on the 16mm mcpcb so you dont have to reflow anything.

You won’t need the glass lens if you have the UV led.

cool. thanks. appreciate the help.