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2023-11: Warosu is now out of extended maintenance.

/diy/ - Do It Yourself

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2542374 No.2542374 [Reply] [Original]

i have a set of lights operated by 3 triple A batteries in a battery pack. problem is, after a single day the batteries are completely dead. any way to plug it into the wall instead?
(picrel)

>> No.2542378

>>2542374
If you get yourself a 9 volt traffo, then sure. Hook it up to the + and - and then attach a plug to the other end.

>> No.2542505

>>2542374
3x AAAs is 4.5V. You could very likely get a USB charger brick (5V), then take an old phone charging cable or micro USB plug, chop the phone end off, and try tying the + and - from that onto the battery pack contacts.

I dicked around with a few cheap 3x AAA lights and I converted them to lithium ion (3.7V) with a USB charging board with the 5V in.

>> No.2542513
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2542513

>>2542374
>>2542505
Here, this actually works with the free blue lights from HF.

I think the only real concern is that you may need a resistor if the lights end up a lot brighter off the 5V USB than the 3x AAAs, the electronics guys would know better.

>> No.2542530
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2542530

I updated to also USB two 3xAA string led lights I had. I kept the batteries space in case I want to use them with batteries, but usually I use them with powerbanks or even usb charger.

Simple setup, I cut and use a USB cable, and I add resistors as other anon mentioned. in the first one I checked the drained mAmpers and added resistors accordingly, to the second one I checked the brightness. Watch out if your lights draw a lot of power to have bigger resistors so they will not get very warm. A really simple and lazy hack. Also a very space economic.

The second string lights had a 3-leg switch so it prevents to use usb and batteries together, it takes power from one or another (no both off option). The first one needs batteries removed before I connect the usb

>> No.2542552
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2542552

>>2542513
I don't know how many LED's OP has in parallel (and how bright each one of them is at 1 or 5mA) but the average warm white LED has a voltage drop of 3V at 20mA (pretty bright). I'd get 5 220ohm resistors (very commonly found in LED kits) and put them all in parallel to eachother (all in series with the LED string), remove one by one until you get the required brightness. If we have 4 220ohm 0,25W resistors (equivalent to a 1W 55ohm resistor) and we know that the voltage drop of the LED's is 3V then we will only have 2V across the resistor (5V from the supply voltage minus the voltage across the LED's). This will give us a current of 36mA which will have to be spread between all the LED's in the LED string. I recommend you fiddle around with the parallel resistors until you get the required brightness and if the resistors get too hot then get the equivalent value of resistor for a higher wattage. There are better ways to control LED brightness but for someone with no electronics experience they aren't very doable.

>> No.2543667

>>2542378
>3 alkaline batteries
>9 volts
Nigger what?!