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.
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.
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