USB LED Lamp circuit.

>> Thursday, June 7, 2012

USB LED Lamp circuit.

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 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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MOBILE INCOMING CALL INDICATOR

Description. This circuit can be used to escape from the nuisance of mobile phone rings when you are at home. This circuit will give a visual indication if placed near a mobile phone even if the ringer is deactivated. When a call is coming to the mobile phone, the transmitter inside it becomes activated. The  frequency of the transmitter is around 900MHz.The  coil L1 picks up these oscillations by induction and feds it to the base of Q1. This makes the transistor Q1 activated.Since the Collector of Q1 is connected to the pin 2 of IC1 (NE555) , the IC1 is triggered to make the LED connected at  its output pin (pin 3) to blink. The blinking of the LED is the indication of incoming call.


Notes. 
  • The coil L1 can be made by making 150 turns of 36 SWG enameled copper wire on a 5mm dia plastic former.Or you can purchase a 10 uH coil from shop if available.
  • The circuit can be powered from a 6V battery.
  • Assemble the circuit on a good quality PCB.
  • C1 & C3 are to be polyester  capacitors.
  • The electrolytic capacitor C2 must be rated 10V.

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