I want to build some kind of an LED lamp/lightbar for on my Flashlight modding bench. The problem is, I have no idea what's involved when driving emitters through 110v. I may still go with a battery system, which I understand, but would like to explore the 110v option.
Could someone show me what kind of driver system I would need to run three or more emitters Using household current.
Do you have any old laptop chargers? 24V ones in particular? I have an old mac charger with 2596 buck driver (wt additional heat sink), powering , 5 series, xte, LEDs on separate heatsinks. At 19.3V output, LEDs receive 1A. This has been going in my room for over a year with no issues. A 1512 Cree cob would be great too. 500 mA at 18.5V and I believe 1A at 20.3V . ( note, my cob has 9 less functioning LEDs so voltage / current values may be different. ) (( The cob is being driven by the xl 6009 boost driver and a 3S laptop battery. It’s only for play so runtime is undetermined)
Exactly what I do. I find the transformer that outputs the closest amount of voltage to how many LED’s that I want to run (in series). Usually from portable phones or laptop chargers. I have several running that have been on for a year or more. I have yet to try putting a driver in for modes. I have had luck with keeping it basic.
I will get about 4 LED’s out of a 12v transformer. String them all together. Snip the plug off the transformer, and wire it up.
Jack 
i also have a 12V adapter from an old NiMH charger powering 3X XM-L, LEDs in the kitchen at a little over 2A. This has been there >2years.
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The 2596 driver and voltage display makes the bedroom light much fun. 
I’ve recently soldered on a small screw onto the pot to make adjusting the output a lot easier. (be careful if you try, the pot doesn’t like heat.) The 6009 boost driver has a 2mm banana socket soldered onto the pot. Lol.
You could use the ESR of a properly-sized Capacitor to “bleed” voltage into your circuit at a low-enough current.
If you substitute LEDs for the diodes in a Bridge Rectifier, you’ll double the perceived flicker rate of the mains supply. (“This one” is OFF while “That one” is ON and vice-versa) If your I and V are within the Reverse limits of your LEDs, you can hook them up parallel but reversed polarity for the same net flicker effect…
But harvesting Wall Warts in addition to batteries from old laptops is much more environmentally friendly, not to mention off-the-shelf easy to do.
How do you control haw many amps the emitters are getting?
If you go for the laptop pack and 2596 buck regulator, you can just dial in the current you require.
I think I have some of these awaiting a similar project.
It spoils the fun, but what's wrong with some decent e27 led bulbs for lighting, it is cheap, and it saves the trouble transforming the voltage down and finding a suitable driver.
Okay guys. I’m over my head with DC current, but I think I get the 12v transformer. Next in line is some kind of a buck driver/current regulator. I’ve been looking at these. Is this what I want, if so which one.
http://www.luxeonstar.com/1000ma-low-voltage-led-drivers
I get you djozz. But if I’m going to build a light, it’ll be functional, but maybe a bit wacky/artsy fartsy looking too. Something I might want to show in the forum.
Remembering Murphy’s Laws of Electricity, among which are that the highest voltage will usually appear on the most-exposed part, and a $5.00 LED will protect a 12-cent capacitor by blowing first, here goes:
Start with a bog-standard Capacitive Power Supply like this, then dike out anything you don’t need. Like, almost all of it.
Full disclosure, I still haven’t tried this, but when I find the right capacitor in some junk, making always-on lights for SWMBO this way is on my bucket list…
On paper, I pared it down to a quite-dangerous 4.4uF cap in series with an opposing parallel pair of ~3.5v LEDs (as a way to get rid of all the old XR-E emitters I pulled for XM-L upgrades) for ~200mA on US power… There’s no protection or anything, and I have no idea what the 120Hz flicker will look like. I was looking for cheaper-than-cheap ways to dispose of recycle otherwise-useless LEDs. … I want to put it in an E14 base, but can’t find a capacitor small enough to fit. And yes, I’m too cheap to go buy one. I was hoping the idea might help.
Ouchyfoot, I measured current to the LEDs with a DMM before soldering the last wire on. The xte LEDs can handle 1.5A so I know that going to 20.5V for a little bit wouldn’t kill them. The heatsink gets pretty hot at 1A LED current (19.3V) so most times, voltage is around 18,5V.
It is the easy way out, that’s for sure.
The innards of 6 E27 LED bulbs. LED star and drivers
The bulbs were 99 cents each on Black Friday at Lowes. Anyone following the Lowes Deal Alert Thread would know that/
Do yourself a favor and get a proper constant current LED driver from fasttech or other vendor.
Select the driver by the forward voltage of the LED module and the desired current. These drivers use transformers that isolate the high voltage mains from the LED.
I think everyone of these guys have excellent ideas. Great info. If you want to know your current for each LED, the charger packs (transformers) always list the voltage and current right there on the pack. Like eebowler does though, check it first just to be sure. I have had a lot of packs test WAY off of their stated voltage/current. That’s where Dimbo the Blinky has good ideas with protection if you should happen to run into that. Edit: I may have misread the protection bit…
I save all I find, they are good for repair work. Read the specs on them carefully though, some have AC output not DC. And some product-specific ones will test at a higher voltage output than specified because the number is meant to correlate with output under a load in use where it will match those numbers. None of them will be exact, there’s no regulation in them.
I’ve got a box full of these babies and now I have another way to use them- I’d not thought about driving LED’s with them :bigsmile: I keep a small 12V back-up power system going here for emergencies but the incan lights I have used are inefficient and the system has to be manually switched over when the power goes out. I think I’m going to do an mains powered relay to automatically switch to battery using a wall-wart to drive some desk LED lighting under normal circumstances and the 12V bank I’m using when power goes out. Should be better light and no darkness ever!
Phil
this
After lots of reading up on this subject, I came to the conclusion that whilst you take a chance on the quality of unbranded electronics from china, on the whole, with flashlight parts etc, you only have a few $$ to lose if it turns out to be crap.
When it plugs into the mains, there’s a whole lot more at stake. Hence why I’d rather use something of known quality to do the mains down to DC bit, then use cheap buck converters.
This is probably the way I should go. I’m not good with electricity, and don’t want to electrocute myself, or burn down my apartment by using a mishmash of assorted component that I really don’t comprehend.
I assume one end of those FT constant current drivers plugs into the wall and the other end leads to the LEDs. I don’t know which one would be proper for me. I’m thinking of running three nichias.