USB LED Lamp circuit.

admin February 23, 2011 19 Comments

USB Lamp Circuit

Description.

Here is a simple USB powered lamp that can be used to light your desktop during power failures. The circuit operates from the 5 Volt available from the USB port.The 5V from the USB port is passed through current limiting resistor R2 and transistor Q1. The base of transistor Q1 is grounded via R1 which provides a constant bias voltage for Q1 together with D2.The diode D1 prevents the reverse flow of current from battery.C1 is used as a noise filter.Two white LED’s are used here for the lamp, you can also use a 2 V torch bulb instead of LED’s. LED D3  indicates connection with USB port.

USB Lamp Circuit Diagram with Parts List.

USB LED Lamp Circuit

USB Lamp Circuit Diagram

Notes.

  • USB port is only able to provide up to 100 mA current.So don’t overload the circuit with more no of LED’s.
  • Before wiring the circuit confirm the positive and ground leads of USB by a multimeter.
  • Switch S1 can be used to turn on the lamp.

We have more interesting USB Circuits that you may like to see;

1. USB Sound Card

2. 12 Volt from USB Port

Comments
  • srinivas
    October 6, 2013

    i didnt understand how it works when i draw this circuit in multisim we didnt got the output any one pls explain this

  • DeeP
    June 8, 2013

    if i don’t want the battery backup than now i have to just remove the battery only or i have to do any other externely changes in ckt

    • Seetharaman
      June 10, 2013

      Hi Deep connect pin 1 of usb to 47 ohms 1/4 watt resistance connect to anode of 2nos white LEDs and their cathode to Pin 4 of USB pin.

  • February 13, 2013

    how approximatery long can our rechargeable battery sustain the leds

  • Sudhir
    February 7, 2013

    LOLzzzz, if you still need to connect a external battery why to put it in USB than. Make a LED torch light instead..

  • RYNO
    April 22, 2012

    Hi
    thanks for the Circuit
    can u Please Share the Datasheet for This Circuit as given in
    5V to 12V converter …

  • LAW
    April 4, 2011

    It works when I give 5V power supply but it doesnt work when I plug into the usb port

  • LAW
    April 4, 2011

    I have made the above usb lamp.
    The lights cannot be turned on when I use 2.4V rechargable battery, however, it is on when I use 3.6 recharable battery.
    Besides, when I plug the usb lamp into computer’s usb port, it doesnt work..why is it like that?

    and thanks for your design =)

  • Seetharaman
    March 17, 2011

    Hi Kailash add one more 1N4007 in series with D2 then the constant current output at Q1 collector will be 30mA . Two Nicad cells fully charged voltage will be 2.64 volt. Connecting the LEDs in series the requirement will be 5.2 volts, which 2 cells cannot supply hence they will not glow. Connect both the LEDs in parallel, then it will work as each requires minimum 2.6 volt to glow. Rechargeable battery is the back up for the LEDs during power failure. The above circuit is not meant for supplying USB voltage to computer during power failure.

  • kailash
    March 16, 2011

    how many diodes and rechargeable batteries in this diagram are required purpose ?

  • Akash mehta
    October 12, 2010

    Where we hav to connect d usb? How desktop can b operated with 5volt battery used in dis circuit? Plz send me some reply.

  • adam
    March 14, 2010

    you can’t connect the LED direct –without current limiting resistor–to the battery

  • Niranjan
    October 31, 2009

    Please tell me, why we use battery b1 in USb lamp circuit….?

    • admin
      November 13, 2009

      battery B1 provides the back up power

  • May 14, 2009

    Umm if the power is down.. is the computer also.., do not take me wrong, great idea and all.. but if the power goes out and by chance the phone line is still live take the lamp off the usb and use it on the phone line 😉

  • zhel
    March 2, 2009

    can you please explain farther the flow of this circuit in a USB lamp

  • jan
    November 19, 2008

    hello. why is there the battery? back-up energy supply when computer is down?

  • Oli Stokes
    September 11, 2008

    THIS IS UBER pWNAGE

  • olasupo
    May 26, 2008

    please where will i connect the 5v of the usb(usb lamp circuits)

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