On 22 Mar 2016, rickman wrote (in article ):
1.5v boosted to 4v (measured) output from the converter. 275 mA (measured) at the battery terminals. I make that to be 1100 mW. If presume 75 percent efficiency, 825 mW.No?
Perhaps I am missing something. The battery terminals will be at the battery voltage, no? So why would you use 4 volts which is at the output? It would be 4 volts times the LED current or the battery voltage times the input current.
-- Rick
Rick
Yikes! Of course you?re right.
Thanks.
From what small ammount of playing with the voltage converters, they are almost like a transformer in action. If you go to a higher voltage, the low voltage current will be a lot more than is used by the load, and if going to a lower voltage , the current from the battery will be less than the actual current used by the load. That keeps the total power drawn the same minus the efficency of the converter.
Sounds about right. If you can light it up, just measure the battery current drain, and calculate or estimate the power dissipation.
If you can remove what I believe to be a lens, I think you'll find that the actual LED is rather conventional and can be found in the Cree catalog. If you sort the above list by power output, there are only 3ea 1w LED's listed. Just find the right die size and good luck soldering the tiny chip. You can also dig throught the current flashlight offerings and see which 1w chips are popular.
Learn by Destroying.... then buy a new flashlight.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On 22 Mar 2016, DaveC wrote (in article):
Just measured working light of same model: using power supply @1.5v (measured at flashlight battery terminals), the current from the ps is 400 mA. Estimating 75 percent efficiency that makes about 450 mW.
So a 1/2W replacement LED might be what I?m looking for.
Thanks.
[Jeff Lieberman]
I found these:
Looks good, no?
Please deduct one point for spelling my name wrong.
No. I thought you said your flashlight was bright and possibly 1 watt. Those are common 5mm LED's with 0.5 watts maximum. These photos look very much like what I would expect to be hiding under what I believe to be a lens of some sorts: This looks a bit closer:
That data sheet is also slightly insane, specifying the luminous flux as: Lumen typ.: 19 mcd Lumens are measured in umm.... lumens, not millicandelas. It is possible to convert between lumens and mcd's using the viewing angle: Anyway, 19 lumens is not very bright but probably good enough for a pocket flashlight.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
And I tried so hard to get the ?Lei/Lie? bit right! (c; 2 steps forward,
1 step back...One of those images (located here):
looks exactly like the one in my light. It?s squat, with very (relatively) large yellow die(?) in the center. I don?t think there?s a separate lens. Maybe it?s molded to focus the light (integral lens)? Wish I could find that LED other than @ Alibaba...
Ah-HAH! From that Alibaba image page: ?strawhat LED?. Search turns up similar-looking LEDs. Searching on the terms ?strawhat? and ?dimple? tells me that this form-factor is for radial distribution of the light, not throwing a beam. Which means the flashlight designer wanted the reflector to shape the beam, not the LED.
So I?m looking for one of these types.
Thanks.
(Why are my search skills so crap? Google keeps returning Manga images and cartoon faces...)
Hmm, that sounds like a good idea to put in my planned LED torch project, which was going to have a manual dimmer anyway. I guess an LDR would be suitable? Maybe mount it in a small tube to make it directional?
I guess I'll have to find an LDR and wave it around with my multimeter attached. Ahh, the dignity of research. :)
-- __ __ #_ < |\| |< _#
News to me. In what way are multi-layer ceramic caps and soldering irons incompatible ?
Not a bit.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Really, before I got my pick and place machine, I hand-soldered about 25,000 .1uF 0805 capacitors. NEVER ONCE had a bad one. I still hand-solder a fair number of low production boards and prototypes, and have never seen a problem with MLCCs.
Jon
Sorry for the delay but I missed the followups to my comment.
Thermal shock easily cracks MLCC caps. I learned that the hard way while fixing several Apple Mac Mini computahs, which feature a collection of MLCC on the bottom of the main board. The original failure mode was shorted MLCC caps caused by either thermal shock or board flex. The bad ones were easy to find with an ESR meter. However, when I tried to install replacements (and guessing the part value because Apple doesn't supply service information to non-authorized repair shops), I managed to crack and short several known good MLCC caps with a soldering iron. Having learned the lesson, I used some solder paste and a hot air SMT reflow gun to do the soldering. I also pre-heated the PCB and let the caps cool down slowly. I don't know if that was necessary, but it worked every time. I'm told that two solding irons used as a tweezer also works, but I haven't tried that yet.
You'll find some more details under: Lots of articles and guidelines on handling and soldering these caps, some of which warn about using a soldering iron. For example:
Damage Prevention When Soldering Ceramic Chip Capacitors Hand Soldering - A pencil type soldering of 30 watts maximum and with a diameter of 3 mm maximum should be used. - The soldering iron tip temperature should be less than 300C [572F] and maximum contact time should be 5 seconds. - The soldering iron tip should never come in contact with the component body. Ever try to solder a small MLCC cap without touching the body with the soldering iron tip? Good luck.
In order to prevent damage (cracks) to the component that can be caused by localized rapid heating and heat shock, preheat the chip, for example, to prevent it from being subjected to heat shock.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I've heard these stories a number of times. And, yes, maybe some people use insanely hot irons or in some other way cause this problem. And, some really large caps are prone to this damage. But, as I say, I have hand- soldered over 25,000 0805 MLCC caps of modest value without seeing this problem. I use a very good Weller temperature-controlled iron, and run it at a modest temperature. Much better to use an iron with really good thermal conductivity at a lower temperature than one with poor conductivity at a very high temperature.
Jon
What does this suppose to mean, do, or prove? Newsgroups: Choose,an,appropriate,group,to,redirect,replies... If you want to black hole replies, just redirect to /dev/null
Newsgroup changed to: sci.electronics.design,sci.electronics.repair
Yep. As James Arthur mentioned, it's not a problem with the physically small caps, which come to a uniform thermal equilibrium rather rapidly. It's only the big caps, with lots of plates, thin low voltage ceramic dielectric, and larger thermal mass, that were a problem for me.
One exception will break any such rule. Dig out a larger and higher capacitance MLCC cap in a 1210 or larger package. Try soldering it with a single soldering iron. Unless you're very good, it won't take much to trash the cap.
"Chip sizes 1210 and larger should be reflow soldered only."
I use several ancient Weller WTCP TC201 and TC202 (because they were free) soldering stations. Most of my tips are 750F with a few at
850F.
I don't understand. All the tips are made of plated iron. There's little difference in thermal conductivity between tips, unless you want to throw in copper tips heated with a gas burner. What part of the soldering iron varies in thermal conductivity?
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
How were the new caps stored? If it is where they can adsorb moisture, you can damage them with an iron that is too hot.
Not at all. That was very interesting. Thanks Jeff and everyone.
Well, I must admit that I didn't take any special precautions. Methinks that the relative humidity in my office runs between 40% and
60% but is not monitored or recorded. Occasionally, it gets low enough to where static electricity becomes a problem, or high enough to where I'm rather uncomfortable, but those are rare. The caps a mix of cut tape and loose bags stored in Ziploc bags (mostly pink anti-static) and in paper coin envelopes. Nothing in hard plastic or metal drawers that might chip or crack them. Although I know that these caps make tolerable hydrometers (and microphones), I don't think they can absorb enough moisture from the air to where a steam explosion would be a problem.I did some digging to see if humidity might be a problem in storage conditions. There were plenty of notes on how a cracked capacitor might allow water to enter the dielectric. Soft (solder) termination is the recommended fix. Some suggests pre-heating the capacitors before soldering to drive off any moisture. One demands that the caps be used within 12 months. I didn't see humidity as being a problem until AFTER the capacitors had cracked. It would take some time for the moisture to alter the capacitor characteristics. With my hand soldering technique, I managed to instantly produce shorted capacitors, which methinks was more likely due to uneven thermal expansion, than to moisture incursion.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I haven't had any problems with cracking but I used to have problems with end caps falling off. I haven't seen the issue for some time, though perhaps it was a problem with the manufacturer. Our purchasing group prefers Murata, so that's what I use (GRM series).
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