The given circuit can be employed as a charging rate indicator by means of a flashing LED. The circuit uses a NE555 timer IC which is wired to generate a square wave which flashes the LED at a normal time period of 1/7 of a second, for an open control voltage or 2/3V at control pin.
Normally the 555 ONs and OFFs when the capacitor voltage discharges to 1/3 and charged at 2/3 of the supply voltage respectively. In the circuit the control voltage pin 5 of the 555 IC is connected to the battery. Any variation in the voltage at the control pin varies the threshold voltage and trigger voltage, thereby the time period of the astable multivibrator. I. e, for increase in control voltage the ON and OFF time also increases.
So as the voltage of the battery increases gradually with charging, the rate of LED flash decreases and in full charge the LED completely stops blinking and be at a steady ON state.Thus the circuit can obtain a flashing light with corresponding to the voltage of battery.
The circuit can be used with a supply range of 4.5V to 16V DC supply, the normal operating voltage range of 555 IC. Here the rate of flashing depends on the difference of the supply voltage and the battery voltage. So while using the circuit the applied voltage should be considered, if the applied voltage is too higher than battery voltage the battery always remains in its standard voltage range even for a full charge, but the LED still flashes. This misguides and results in the overcharging of the battery. So make sure that the applied voltage is nearly equal to the voltage of the battery in the limit of 555 operating voltage, then only the circuit can obtain a proper rate of flashing.
Normally the 555 ONs and OFFs when the capacitor voltage discharges to 1/3 and charged at 2/3 of the supply voltage respectively. In the circuit the control voltage pin 5 of the 555 IC is connected to the battery. Any variation in the voltage at the control pin varies the threshold voltage and trigger voltage, thereby the time period of the astable multivibrator. I. e, for increase in control voltage the ON and OFF time also increases.
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| Battery charging rate indicator circuit diagram |
So as the voltage of the battery increases gradually with charging, the rate of LED flash decreases and in full charge the LED completely stops blinking and be at a steady ON state.Thus the circuit can obtain a flashing light with corresponding to the voltage of battery.
The circuit can be used with a supply range of 4.5V to 16V DC supply, the normal operating voltage range of 555 IC. Here the rate of flashing depends on the difference of the supply voltage and the battery voltage. So while using the circuit the applied voltage should be considered, if the applied voltage is too higher than battery voltage the battery always remains in its standard voltage range even for a full charge, but the LED still flashes. This misguides and results in the overcharging of the battery. So make sure that the applied voltage is nearly equal to the voltage of the battery in the limit of 555 operating voltage, then only the circuit can obtain a proper rate of flashing.
Components required
IC1- NE555
Resistor
R1,R3 - 1k
R2 - 10k
Capacitor
C1 - 10uF
Diode
D1 - LED
D2- 1N4007
Diode
D1 - LED
D2- 1N4007
