Saturday, October 4, 2014
3 6 Volt Cell Phone Battery Meter
This is a agnate ambit to the aloft and provides a 4 LED bar blueprint advertence the voltage of a accepted 3.6 volt Lithium – Ion recharable corpuscle buzz battery. The advertence voltage is provided by a TL431 programmable voltage antecedent which is set to 3.9 volts area the TL431 connects to the 1K resistor. The lower advertence for the LED at pin 14 is set with the 5K adjustable resistor.
The programmed voltage of the TL431 is formed out with a voltage affiliate (10K 5.6K). The acclimation terminal or alliance of the two resistors is consistently 2.5 volts. So, if we use a 10K resistor from the acclimation terminal to ground, the resistor accepted will be 2.5/10000 = 250uA. This aforementioned accepted flows through the high resistor (5.6K) and produces a voltage bead of .00025 * 5600 = 1.4 volts. So the blow adapted achievement voltage at the cathode of the TL431 will be 2.5 + 1.4, or 3.9 volts.
Working out the LED voltages, there are three 390 ohm resistors in alternation with addition adjustable (5K) resistor at the bottom. Assuming the basal resistor is set to 2K ohms, the absolute attrition is 390+390+390+2000 = 3170 ohms. So, the resistor accepted is the advertence voltage (3.9) disconnected by the absolute resistance, or about 3.9/ (390 + 390 + 390 + 2000) equals 1.23 mA. This gives us about .00123*2000= 2.46 volts for the basal LED, and about .00123*390 = .48 volts for anniversary footfall aloft the bottom. So, the LEDs should ablaze at accomplish of 2.46, 2.94, 3.42, and 3.9. A absolutely answerable corpuscle buzz array is about 4.2 volts. You can acclimatize the 5.6K resistor to set the top voltage college or lower, and acclimatize the lower 5K resistor to set the basal LED for the everyman voltage. But you do charge a 6 to 12 volt or greater array to ability the circuit.
Saturday, August 30, 2014
USB Mobile Phone Battery Charger Circuit
But low accepted charging is bigger to access the ability of the battery. The ambit declared actuality provides 4.7 adapted voltage and acceptable accepted for the apathetic charging of the adaptable phone. Transistor Q1 is acclimated to accord the adapted output. Any average ability NPN transistor like CL100, BD139, TIP122 can be used. Zener diode D2 controls the achievement voltage and D1 protects the polarity of the achievement supply. Front end of the ambit should be affiliated to a A blazon USB plug.
Connect a red wire to pin1 and atramentous wire to pin 4 of the bung for accessible polarity identification. Affix the achievement to a acceptable charger pin to affix it with the adaptable phone. After accumulating the schema, admit the USB bung into the atrium and admeasurement the achievement from the schema. If the achievement is OK and polarity is correct, affix it with the adaptable phone.
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Tuesday, August 26, 2014
CELL PHONE CONTROLLED AUDIO VIDEO MUTE SWITCH
When the cell phone is in its holder, LDR1 does not receive any light from white LED1 and its resistance is high. As a result, the voltage at pin 2 of IC1 remains high to provide a low output at pin 3. The low output of IC1 activates relay RL1 and the audio/video system gets power supply via its N/O contacts. LED3 glows to indicate that the audio/video system is ‘on.’When the handset is taken off the holder, light rays from LED1 fall on LDR1 and its resistance decreases. As a result, the voltage at pin 2 of IC1 decreases to provide a high output at its pin 3. The high output of IC1 deactivates relay RL1 and the audio/video system does not get power supply. LED2 glows to indicate that the audio/video system is ‘off.’
Preset VR1 is used to control the sensitivity of the schema. Zener diode ZD1 is used for protecting white LED1 from the higher voltage. The schema works off a 12V car battery. Switch S1 can be used to manually switch on/off the audio/video system.