Convert: Solar LED Fairy Lights to USB power

Convert solar powered string LED lights to be USB powered, run brighter and last much longer per charge.
These lights are no longer suitable for use outdoors once converted unless you use a waterproof housing for the USB power source!
This is the second upload of this video, thanks to Martin Webster for highlighting an error in the first upload :-)

[@mspalding4605]

Very helpful. Thank you!

[@isoguy.]

In the vid you said that we know V=5V, okay that's printed on my poundland power bank, given. Then you went on to say:- We know I=80mA but I don't have a bench power supply! What assumptions can I make for my white LEDds? I would like to try this project on 50 LEDs so I really would like to know how to find "I" so that I can calculate the correct resistor for my LEDs. Would an 1/8W or 1/4W etc. resistor be needed? And how would I calculate this for my 50 led string? Sorry to be a pain but would appreciate the extra info. Really useful vid and thanks for sharing this useful project.

[@childscraig]

Hi ISO Guy, You can measure the current with a multimeter, it doesn't need to be a bench supply (that's just an easier way). Most multimeters have current measurements, you need to check the instructions on yours (assuming you have one or can borrow one). The meter is used inline so you need to break the circuit and complete it with the meter in the right mode, this should give you the I value for your lights. Most multimeters require you to change where the probes are connected for current measurement, remember to put them back before trying to read voltage otherwise you might damage your meter! I hope this helps, Craig

[@isoguy.]

@@childscraig A friend of mine (an electrician) and he is going to give me his old multimeter. Now thats a bonus. He is going to drop the meter off on Monday on his way to work so my project will have to wait till then. Thanks for the additional tip. Great vid

[@tsvandyke]

@@isoguy. in the US ... Buy any item - get a multi-meter FREE - " Harbor Frieght Tools "

[@jonieevangelista]

sorry for the noob question, resistor is to avoid it from getting burned right? i have this type of led strip, 5 meter - 50 leds...i have soldered it directly to usb without resistor, some led got burned some are not...if i'm going to do what you did here, am i still gonna burn the other led? or this is actually the solution to my problem - i am going to remove the broken ones and solder them again with fine ones...thank you!

[@childscraig]

Hi, you are correct that connecting directly to USB without adding a resistor has caused some of your LEDs to fail, the resistors limit the current flowing through the string. If you remove the broken ones and add the resistor the rest should work, they may have a shorter life as they may have been damaged by the unrestricted current, only time will tell. Good luck!

[@BarnOwlCat]

Hi Craig, thank you for such an informative and to the point video! I accidentally bought solar powered fairy lights from Ebay. Confusing listing where two of the three lengths was battery while the one I chose was solar. I do have a question, how do you know which string on your fairy lights are positive and negative? Thank you once again.

[@childscraig]

Hi Sarah, You would normally take note of this before you disconnect the lights from the old supply, the positive and negative on the old battery would help identify this. If you have already passed this point it's still not a problem, as long as you have fitted your resistor the LEDs will only light when connected the right way round, connecting them the wrong way round should not do any damage as long as the resistor is in place and the voltage you are connecting them to is the right level. Hope this helps, Craig

[@thenightowl1588]

Finally I found this video that explains briefly about the needed resistor. I helps a lot. Thank you.

[@nil0bject]

hey, can you redo this video with the solar chargers that take 3 batteries? replace the AA's with a lipo? add a esp32? inside the solar case to remain weatherproof?

[@thenightowl1588]

*I mean it helps a lot.

[@dnbshaggy]

I've got several sets of these crappy solar lights, could I connect them all to a single USB? They all use very similar solar boxes with single AA batteries inside.

[@Alex-os5co]

This is an excellent video explaining everything, thank you! When you say you bench tested the brightness you liked am I correct in saying there is no danger in applying a 5V 1amp USB charger to a string of xmas 200leds. They were powered by a 1.2V 400milliamps? Thanks!

[@childscraig]

Hi Alex, You would need to modify the resistors before you applied that power source, the increased voltage would quickly burn out the LEDs if you don't. When I bench tested the brightness I used a voltage and current regulated power supply to work out the values I needed, you can measure how much current your lights are drawing with a multimeter, from there you can work out which resistor values you would need to drive your string of lights. Just remember, the brighter you run an LED the shorter it's lifespan. Hope this helps.

[@Alex-os5co]

@@childscraig Wow thank you for your response and help. Liked and subbed. I decided on a 480ohm resistor to achieve 12V power supply (so I can use a Shelly 1 ) and they draw 0.025amps. Cheers!!

[@sauljose8783]

Commenting for future project!! Seems that I will need to read this thread

[@perthkraya3209]

​@@sauljose8783so am I .

[@peterthomson3393]

Craig, love these videos. I have a LED string light curtain with horrible combination mode nonsense. I just want to flick switch and they are steady on. Would this method work for this to bypass the need for always having to manually switch on?

[@childscraig]

Hi Peter, This method only changes the power source, it doesn't alter the control at all. Changing the control is a whole other topic and honestly usually more hassle than it's worth given that you can buy static sets very cheaply. Best wishes, C.

[@x4dd]

What about a string of multi function lights....only every other bulb lights when converted to USB 5v?

[@childscraig]

That sounds like you have the type of light featured in my other video: kzbin.info/www/bejne/pJOWfal7rrRlgMU

[@imho2278]

Run 2 resistors together to get 94 ohms.

[@imho2278]

A lot of leds need .06mA to function.

[@iimnana]

Really love how you show the calculation😍 but I didn’t get it where 8 mA comes from, so would you please explain that?😃

[@childscraig]

Hi Limnana, 80mA is the power consumption of the LEDs before we modify them, you can measure this using a multimeter inline with the circuit before you take the unit apart. In my case I have a bench power supply which I can use to show me the voltage and current however you can do the same measurement with a multimeter in A/mA mode. I hope this helps, C.

[@iimnana]

Craig Childs Thank you so much ☺️☺️

[@OctiveKyla]

Love the Tech Bit. Keep going on being awesome!

[@tsvandyke]

9:27 ... " If you do this ... you CAN"T put it outside anymore.... as it is NO longer weather resistant" ( but that's exactly why I want to do this - to make my garden / pathway lights work longer & brighter )

[@childscraig]

Hi there, You can put the new setup in a weather resistant enclosure and put it outside, that is an option. C :-)

[@tsvandyke]

@@childscraig YES ... but I was watching the video for that exact reason .. .then waited until the 10 minute mark to say ... " if you do this - you can't use it for the original purpose anymore." ... so what is the point of making something - if you are REDUCING the options .. it is like saying ... you " could " ... buy a BMW - & use it as a mobile plant stand - if you make a few modifications to it ... like cutting off the roof.

[@tsvandyke]

@@childscraig IF I need to buy an additional enclosure ... I am spending MORE than a $1 ... Which is the POINT of the video ... making a $1 item - Better .

[@rcristy]

There's a lot of line before the join, just leave the join under cover.