smart phone light circuit diagram


Posted on Feb 7, 2014

The circuit shown here is used to switch on a lamp when the tele- phone rings, if the ambient light is insufficient. The circuit uses only two ICs and it can be implemented very easily. A light dependent resistance (LDR), with about 5 kilo-ohms resistance in the ambient light and greather than 100 kilo-ohms in darkness, is at the heart of the circ


smart phone light circuit diagram
Click here to download the full size of the above Circuit.

uit. The circuit is fully isolated from the phone lines and it draws current only when the phone rings. The circuit provides automatic switching on of a lamp during darkness when the phone is kept in a place such as the bedroom. The lamp can be battery powered to provide light during power failure or load shedding. This avoids delay in attending to a call. The light switches off automatically after a programmable time period and it needs no attention at all. If required, the lamp lighting period can be extended by simply pressing a pushbutton switch (S1). The first part of the circuit functions as a ring detector. When telephone is on-hook, around 48V DC is present across the TIP and RING terminals. The diode in the opto-coupler is off during this condition and it draws practically no current from he telephone lines. The opto-coupler also isolates the circuit from the telephone lines. Transistor in the opto-coupler is normally off and a voltage of +5V is present at the ring indicator line. When telephone rings, an AC voltage of around 70-80V AC, which is present across the telephone lines, is used to turn on the diode inside the opto-coupler (IC2) which in turn switches on transistor inside the opto-coupler. The voltage at its collector passes through 0-volt level during ringing to trigger IC3 74LS123(A) monostable flip-flop. The other opto-coupler (IC1) is used to detect the ambient light condition. When there is...




Leave Comment

characters left:

New Circuits

.

 


Popular Circuits

Tone-control audio amplifier
Thermocouple Temperature Control
CAN bus line communication modular design of one-chip computer and MCP2510
hygrometer
4 i n 1 burglar alarm circuit diagram
Four phase stepper motor drive system
Infrared remote control relay circuit b



Top