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Smartphone light

2014-12-09 19:11  
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Next is the smart phone light. The most effective way is to grasp the principle of combining schematic view text, combined with text to understand the principle. See figure: a photosensitive resistor (LDR), approximately 5 kg ohm resistor in ambient light and harmfulness 100 kg ohms in darkness, is the heart of the circuit. This circuit is completely isolated from the phone line and it draws current only when the phone rings. This circuit provides automatic switching of lights in the dark when the phone is placed in the bedroom and other places. This lamp can provide light in the battery-powered power failure or load shedding. This avoids delay in attending a call. Light switches off automatically after a programmed time and it does not need attention. If necessary, that lamp lighting can extend the period by simply pressing a button switch (S1). The first part of the circuit functions as a ring detector. When the phone is on-hook, about 48 v DC exists throughout tips and Circular Quay. This diode optocoupler so is 'off' in this condition and it has attracted almost no current from his phone line. Optocoupler isolation circuit, also from the telephone line. Transistor optocouplers are usually 'off' and a voltage of 5 v attending a ring indicator line. When the phone rang, an AC voltage of about 70 - 80 v AC, which is present throughout the telephone line used to open, such as optocoupler diode (IC2), in turn switches on transistor optocouplers. In its collector voltage is 0 volts level ringing trigger IC3 74 ls123 (A) monostable trigger. Others, such as optocoupler (IC1) is used to detect ambient light conditions. When there is enough light, long distance relationship with a low ohmic resistance of about 5 kg and transistor optocouplers in 'state. When there is not enough light, the resistance increases, the loan-deposit ratio megabytes ohms and the transistor switches to the OFF state. Therefore, the DC voltage appears at the collector of transistor optocouplers, etc. are usually 0 v, it rose to 5 v When there is no light or low light. 74 years ls123 retriggerable monostable multivibrator is used to generate a programmable pulse width. First monostable  74LS123 (a) generates a pulse trigger input can be used in the ring, pin 2 to provide their input (labeled B) is a logic high (ie in the dark). It is still high programming time and switches back to 0 v at the end of the pulse period. This low transition (edge) is used to trigger the second monostable multivibrator 74 ls123 (B) in the same package. The second monostable output is used to control the relay. Lights are controlled through the N / O relay contacts will be exchanged "." In the "period can be extended, simply press the button switch S1. If no one attended this phone, lights are switched off automatically after a certain period of time equal to the pulse width The second trigger. photosensitivity distance relationship can be changed by changing the resistor R2 is connected between the collector transistor in the optical monitoring circuit. Similarly, the ON period can be controlled by changing the lamp capacitor C3's value in the second 74123 ( B) monostable circuit and this principle is simple but effective and you can read several times to grasp the principle.
 

Smart Phone light

Smart Phone light

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