What will do if you want a low voltage less than 3 volts as reference voltage for a circuit? Usually we use a low volt Zener to give low voltage to a particular section of the circuit. But Zener below 3.1 V is not available. So do this simple method. The LED can act a Zener to give a reference voltage. Each type of LED has a forward voltage drop that range between 1.7 V to 3.3 V. This forward voltage drop slightly increases when the input voltage increases. This is due to the increase in the luminosity of the LED. So let us exploit the LED to do the job of the Zener.
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This simple White LED lamp switches on when its surroundings turn dark. It is an ideal portable lamp in picnic sites. It uses solar power for charging the battery and an LDR for automatic switching.
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Here is a simple Solar Night lamp that turns on automatically at sunset and stays on till morning. It uses 1 Watt High Bright White LEDs to illuminate a confined area.
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Here is a High efficiency Emergency Lamp using High bright White LEDs. It automatically turns on when power fails and turns off when power resumes. It is powered by a 6 volt 4.5 Ah rechargeable battery which can power the LEDs for a long period.
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