USB powered string of LEDs with clever current sharing trick.
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- Опубліковано 7 лис 2014
- I bought these as a convenient source of long parallel arrays of LEDs suitable for hacking into outdoor solar lights. I was expecting it to be just a USB plug, resistor and the parallel string of lights, but it turned out quite intriguing.
Firstly, the current was higher than expected at 800mA (8mA per LED) and there's no resistor!
Further investigation found that three wires were used along the run so that the positive side of the array was fed from one end and the negative side of the array was fed from the other end. This has two functions. The combined resistance of the feed and return wire to the far end acts as the resistance, and this arrangement results in even brightness along the full string instead of being brightest at one end and tapering off along the string due to the increasing resistance and voltage drop.
Fancy these for my mini office station at home.
I built the station some 15 years ago but had not seen the LEDs I was looking for to finish the lighting.
Found them!
Thanks Clive.
Clever. I try to do that 'diagonal' setup whenever I have batteries(and sometimes other stuff) connected in parallel. It's one of the recommended ways to connect batteries in PV systems.
It isn't actually perfect. One get the same resistance to each battery(or LED, or whatever), but not the same voltage drop through the cables between them as the currents differ.
i'm trying to find a way to power a LOT more than 100 tiny LEDs with a power source which has to be extremely light weight. battery packs are way too heavy. to use. I suck at electronics but these look to be a step in the right direction. Thank you for talking about these cool lights.
Yeah, so I made the mistake of installing some of these and having an excess so cutting it to length. I thought I could just cut a segment out (about 4% of the length) and reconnecting them again. this blew some of the LEDs instantly, causing a short in the length. also the power supply was rated at 18v 300mA but included cc after the mA so I made the assumption this meant Constant Current. anyway after removing the damaged LEDs from the string about 3 of them I powered it backup with a 300ohm to limit the current. and try workout where I went wrong. I found out this strange setup. also the ones i am using are also staggered into 3 sections. anyway after all the repairs to it I had to order new ones anyway as I had damaged them beyond appearance repair. I just thought this was a wired design. thanks for all the videos!
Brilliant...thanks !!!!
I have the same thing using slow color changing leds, but they do not use 3 wires. Just two wires, and a single resistor. I ran one for a year and the clear plastic around the usb plug browned from the heat.
...and that answers my question "Can I just clip off a few feet from the end for a shorter run of lights?" If they had been wired in parallel (with two wires) it would have been no problem, though the remaining lights would have had more current running through them. With this three wire setup I'd have to re-join the return ground at the end of the string to make it work correctly - though again there would be more current running through the remaining LEDs.
I charge multi cell batteries in parallel using this technique, think of the cells in place of the led's, in a standard parallel charge the voltage will drop as it goes along the cells till basically the last cell has less charge than the first, but the configuration your showing with these led's cancels that out.
My mother has got 4 of these strings of LED lights
2 copper ones and 2 silver ones
Can we cut in to two and connect to an other USB port plz reply i have 15 meter one 😊
I have a set of LED lights for fishing. They have a 3 ft tinned copper lead wire. When I connect them directly to a 12 volt agm battery the current draw is 5.2 amps. When I add any length of wire to lengthen the circuit the current drops to 2.6 amps. The amount of visible light is greatly diminished. Can you please help me. Thanks in advance!
Can I cut them up into shorter segments and reconnect the wiring so that it will still be a parallel circuit and will still have the third wire serve as a resistor? I plan to put them on small jars powered by AA batteries. The one's I plan to get have a 100 bulbs running on 12V
I have the same question. Working on a glass bell project but such a long string of LED is just to big for me. I actually only need 5 to 9 LEDs in one circuit.
Hi! I have solved this problem already. Answer is yes, but you have to cut it where the parallel circuit is in series with the other parallel circuits. In my case, there are 3 wires always "connected" to or running through the LEDs except for some segments where there are 2 LEDs only connected to each other with 2 wires. Cut between these LEDs.
These will leave you with 2 sets of open wires. Close the circuit by connecting the open wires at the end of the circuit with the batteries. The other set of open wires are where you'll place the new sets of batteries to power the remaining circuits. Repeat.
The one I bought contained 50 bulbs. The parallel circuits had 13-12-13-12 LEDs each. So I had to cut between LED 13 and LED 14, LED 25 and LED 26, and finally LED 38 and LED 39.
I hope this helps!
Thank you! I will try this out.
I have four separate solar powered 5m copper wire led strings. They are all failing. Can I cut the strings from their solar box panels and power the loose strings using a central alternative power source e.g. A/C. What would you recommend so that I don't have to depend on failing solar batteries every now and then.
My tiny led 3meter by 3 meter is not working. It has a usb which i connect to my phone charger, but light stops after an hour ,I tried different phone chargers, some chargers gets heated.
Shall i buy some different voltage phone charger. 110 v -240v is all usb led lights they should work on phone chargers.
Would a multi-function controller version of these be 3 true wires then or is there cleverness for making these do pwm in some fashion?
At least i wont blow my powerbank from the currect that these fairy lights make.
Can you please try a cheap 26cm ring light as it does not indicate the current it consumes and how many watts it is... I have a 26cm ring light that blew the ic chip on my powerbank
hi clive just got some at quid shop but only in 1 meters so was thinking of joining all together .will i get away with useing a 5volt 2amp power supply and just putting a resister in series with the psu it will work out the same amount as your string with me having 10 per meter bonus is i will have 10 little aa power boxes to use for projects when i chop all the strings off them.what do you reakon clive .....
The LEDs in these strings tend to be exactly voltage matched per string, so I don't know how consistent the intensity will be along them. They'd probably all have to be the same colour (The Poundland ones are available in white, blue or multicolour) to get as close a voltage match as possible.
A 10 ohm half-watt resistor will run the lights at a total of about 200mA, which should be ideal for anything from 20 LEDs to 100. You may have to guess the polarity and try it out when you join them.
I just saw your video with "LED tape voltage drop on long runs." before this one. Could the same strategy apply to a LED tape? Connect positive to one end and negative to the other. Running extra wires along the LED tape seams a bit of a head ache, especially if the LED tape is in a loop and you have both ends in the same place.
I see people have found them. Where are they looking? I would like to buy.
Hi Clive, it's Christmas Eve and a have a string of 120 LEDs powered with 2C batteries. There was an accident and the end of the string broke off with the battery box and a 1 light. I know noting about circuitry and tried twisting the ends together and see that doesn't work. What would I need to do to get the string working again? I would be grateful for your advice in elementary terms.
If they are these wire lights then if there are two wires at the end then they are not connected. If there are three then only two of them will be connected. There will be a single wire looping along that doesn't connect to any of the lights and a pair of wires that connect to all of the lights. If you scrape the insulation off the wires and then touch the loose wire to each of the light-wires in turn then hopefully one will make them light. If you get them to light then twist those wires together and cut the other one back out of the way.
Clive - you saved Christmas! I folded a nail file in half, pinched and pulled the wire ends through it a few times which removed the invisible insulation and Voila!
Merry Christmas Clive! (and all the best for 2017!)
I can see cleary in video if there's a resistor. Can I connect led directly to USB WIRE?
You need a resistor to limit the current through LEDs.
i am operating this from my mi power bank 2. it worked well at 1st and.then got dimmer. is there any way to fix it?
That could be two things. A resistor that has cooked and gone higher resistance, or rapid degradation of the LEDs if they were being driven hard.
I bought 100 bulbs usb leds copper one, it was fine, then i accidentally cut it into half,
The one half with usb plug is only lighting other half totally inoperable , since its pure copper string not a regular wire , even if i tried to connect it, but couldn't attach the broken half portion of led string.
Need ur help
I have videos about repairing the copper wire lights. There is clear lacquer on the wire that needs removed, and the wires must be round the right way.
Hello, I have solar multicolor(blue,green,red, warm) fairy lights and it also have 3 wires too, I want to convert it into usb, when I try to connect the two wires of fairy lights the blue and green only shines so I try to connect the 3rd wire but the red and warm only shine. What should I do? I'm confused.......
Try different wire combinations. It's possible they are the alternate polarity type and need a low voltage AC output from a controller to run them.
I have a 10 meter one of this string light. I can't find a longer one in our online store. Will it be alright to connect a 10 meter and 5 meter one together?
It depends on how it's configured. If they both operate at the same voltage you may be able to power both from the middle.
@@bigclivedotcom thank you so much for your reply. Have a great day :)
How to connect two such strings together?
could you post a link to these I can't seem to fint them on e-bay?
Do an ebay search for USB 100 LED string and you should find them. But be aware that your search will have to include worldwide sources, since they only seem to be common from China at the moment. Delivery from China will generally take about 3 weeks.
bigclivedotcom www.ebay.co.uk/itm/390956888745
thanks for the reply clive ,what i dont get is why the leds dont draw more than 30-40 ma per string of 10 when there is no resister at all and they are just a possitive and negative line with the 3 volt battery.i have current checked all my strings and they all draw between 31-42 ma at around 3v
The voltage of the LED is very close to the battery voltage on these strings, so if you inserted a meter in line then its low resistance would still have affected the current reading quite significantly. That said, even at very low currents the LEDs will still appear bright.
I purchased some copper wired micro fairy lights wired to 3 x 1.5 batteries, I wanted to use them with a usb lead so I soldered the black and the red wires of the usb to the micro lights, plugged them in to my usb plug and found they were getting very hot. Then they all blew one by one what can I do please,
Add a 10 ohm resistor in each lead between the power supply and lights.
@@bigclivedotcom Thanks I thought that would be the answer, much appreciated. Thank you
I brought the same string lights Of 10M and i wat to use it as usb power string lights how to do it
I have some and only every other one works. When I change polarity the ones that weren’t lit up before are now lit up, but again every other one. Does anyone have any ideas?
Those are the "chasing" type. Two channels from swapping the polarity.
bigclivedotcom I never thought of that. Yes, I liberated them from the control box for a project. Don’t suppose you have any idea how to make them all work on a dc current. I only see a pair of wires.
Can you connect a 200 light set of solar fairy lights to a 200 set of fairy lights that you plug in? I found your video fascinating. But I'm 66. I don't remember much electrical theory from my junior year of physics. Thank you.
Not really. The solar ones will be wired in parallel and unlikely to be rated for mains voltage.
@@bigclivedotcom thank you.. I'm glad I asked..
I'm wanting to take my battery charged string and attach them to my plug in one. Guess I learned something else instead
bigclivedotcom Are you going to make a test of a LED Flashlights? I`m really intrested in flashlights. It would be nice to see you testing some of them. I have 3 flashlights at the moment :P all with Cree XM-L leds, they are very powerful (around 10W)
There is a interesting forum about flashlights "budgetlightforum" you can check them out if you want.
I'll keep that in mind, because I do like flashlights. But the Internet has a lot of flashlight teardown videos from real flashlight geeks.
bigclivedotcom Convoy flashlights ale pretty well made and cheap (15-20$)
Back to LED bulbs. Could you make a Osram LED bulb (E27 type) teardown? Are these avaible in your country? I couldn't find any Osram teardown videos, so I wonder what quality they are.
but all leds get higher current than that of 2.5 ohms.
I have 1 meters wire led string, and tested to modified for portable led, and i put on the battery 2000mah And finally it's broken, it doesn't work
I rewatched this a dozen time, and you definitely did not explain well what that 3rd wire is doing. I don't get it. Would love to get it, but I don't.
By feeding positive from one end and negative from the other, the amount of wire (resistance) in series with every single LED is equal.
@@bigclivedotcom
@bigclivedotcom I'm working on a string light project, and I'm not well versed in this stuff, so thanks for your effort, my man🙏. My lack of understanding is likely the bigger problem here, I'll admit.
What I still don't get is that I read that wiring components in parallel, like the string light in this video, has the advantage of evenly distributing the voltage to all the components, as opposed to when being connected in series. Maybe this true of voltage, but not "current" or resistance?
ps i got 10 strings of 10 leds
MmmmmKay