Projects/Create a nightlight from old usb charger

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Usb nightlight.jpg

So everyone has a bunch of USB chargers lying around. This is a simple way to make a simple nightlight with only a few parts.


  • USB charger
  • USB cable
  • white LED
  • resistor


  • Find a white LED, and note the forward voltage (VF) and max forward current (IF-max)
    • if you don't know the voltage and current, you can try VF=3.5V, and IF-max=20mA, and see if it's bright enough
  • Calculate needed resistor
    • R = (5-VF)/IF-max
    • select the closest available resistor
  • Cut and strip the usb cable
  • Solder the components together in the following order
    • USB's red wire -> resistor(R) -> LED(+) -> LED(-) -> USB's black wire
    • LED positive lead is the longer, negative lead is on the side of the LED with the sightly flat side on the bottom
    • You can just twist the wires and leads together, instead of soldering, just be sure they won't come apart, and insulate them well.
  • Insulate the wire and solder joints
    • Heat shrink tube works best
    • Electrical tape is OK, but can shift over time
  • You can let the led dangle from the charger, or put it in a clear/translucent cap or cover
    • remember LEDs are very unidirectional so point the LED towards the ground or the direction that works best for you.


  • you can add a darkness detector by adding a transistor(NPN BJT) and light-dependent resistor(LDR), but the LED/ON power usage is around 0.1W, so I didn't see the point.


  • total power usage for my adapter was 0.4W