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  • avd80 commented on avd80's instructable Simple Solar Day Lamp which lasts for 15 years3 months ago
    Simple Solar Day Lamp which lasts for 15 years

    It is a 1 Watt White LED. It provides between 30 to 45 lumens when forward current is 350 mA

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  • avd80 commented on avd80's instructable Simple Solar Day Lamp which lasts for 15 years6 months ago
    Simple Solar Day Lamp which lasts for 15 years

    Dear diy_blokeYour question is very valid. A 12 V PV panel actually has a voltage rating of 17 V at maximum power. It has an open circuit voltage of about 20V. Why it is called as 12 V PV panel, my guess is, it is used for charging 12 V battery. The 15 ohm resistor is designed as a worst case value. In summer the panel may generate much more than 5 W of power. That is because, 5 W rating is specified at standard condition of 1 kW solar power per 1 sq meter area. In summer the solar intensity goes well beyond that. Which means the PV panel may supply more than 19 V at full load. Taking this into account 15 ohm resistor is included. Normally, the LED current is in the range of 150 to 250 mA range. This provides good light output. If more light is required kindly see the article "High...see more »Dear diy_blokeYour question is very valid. A 12 V PV panel actually has a voltage rating of 17 V at maximum power. It has an open circuit voltage of about 20V. Why it is called as 12 V PV panel, my guess is, it is used for charging 12 V battery. The 15 ohm resistor is designed as a worst case value. In summer the panel may generate much more than 5 W of power. That is because, 5 W rating is specified at standard condition of 1 kW solar power per 1 sq meter area. In summer the solar intensity goes well beyond that. Which means the PV panel may supply more than 19 V at full load. Taking this into account 15 ohm resistor is included. Normally, the LED current is in the range of 150 to 250 mA range. This provides good light output. If more light is required kindly see the article "High Power Solar Day Lamp" in instructables. Usually, the life of LED depends upon the current flowing through it. So, if lower current is flowing through the LED it will have longer life.Lastly, even during cloudy days with sufficient light, these PV panels do generate good open circuit voltage which is greater than 15 V. Hence the LEDs will always be forward biased and will be ON. The intensity of light from LEDs may be lower. Until the sunlight intensity goes very low such as in the evening, we keep getting light from the LEDsI hope I have clarified to your satisfaction.Thanks-Abhijeet

    Dear diy_blokePlease have a look at one more add-on feature for solar day lamp at following link:http://electronicdesign.com/power/solar-day-lamp-also-powers-fm-receiverThanks-Abhijeet

    Dear diy_bloke,Please have a look at one more feature for day lamp at following link:http://electronicdesing.com/power/solar-day-lamp-also-powers-fm-receiverThanks-Abhijeet

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