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    Here is the simple solution to make an automatic solar powered led lamp. It automatically switches on two high power White LEDs in the evening and stays on for 6 hours using a 6 volt 4.5 Ah rechargeable battery.

    A 12 volt solar panel is used to charge the battery during day time. The battery is connected to the input line through the NO and Common contacts of the relay. Diodes D1 and D2 drops 1.4 volts and charge indicator LED uses 1.8 volts. Relay also drops some voltage so that around 8 volts will be available for charging the battery. The high value (4700uF) Capacitor C1 act as a “buffer” for the clean switching of the relay and also prevents “relay clicking” when the input voltage reduces momentarily.

    Schematic of Simple Solar Lamp Circuit

    Simple Solar Lamp Circuit diagram

    During day time, the solar panel generates 12 volt DC which makes the relay active and the NO (Normally Open) contact makes connection with the common contact. This completes the current path to the battery. Two 1 Watt power LEDs are connected to the NC (Normally Connected) contacts of the relay. When the relay energize, the NC contact breaks and LEDs do not get power. Resistor R2 (18 Ohms 1 Watt) drops the LED current to 330 mA. The LEDs are rated 350 mA at 3.6 volts. With 3 volts and 250 mA current, these LEDs can give adequate brightness.

    1 Watt Power LED

    In the evening, current from the solar panel stops and relay de-energize. At the same time, the NC contact of the relay gets power from the battery through the common contact and LEDs turn on. Theoretically, the battery can power 12 hours with 350 mA current, but the battery voltage and current reduces drastically. So it is better to turn off the lamp after 5 or 6 hours using the switch S1.

    Use a small 6 volt 100 Ohms PCB relay to make the lamp unit compact. The Solar Lamp circuit including the relay can be enclosed in a small box. If a reflector is fixed behind the White LEDs, intensity of light can be increased. Use jack and socket to connect the solar panel with the circuit.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    21 Responses to "Solar Powered LED Lamp Circuit"

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    1. Dear Mr. D.Mohankumar,

      This circuit design is very good, but can you please give low battery protection of this??? as many a times it is not possible to switch off the unit. Also what wattage of solar panel is to be used, and by what mA will the battery charge, as the sun light shines only for few hours i.e. 4 to 6 hrs, and max charging will be done at that time only.

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      • D Mohankumar D.Mohankumar says: on September 12, 2010 at 2:47 pm
          member

        Battery protection circuit is not included to make the circuit simple. You can use any battery protection circuits given in the posts. Solar panels are available from 1 watt onwards. A 5 watt is sufficient. The charging current depends on the illumination. It may vary from 50 mA to 300 mA. Battery will get sufficient charge if a 12 volt 5 watt panel is used.

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      • Hello Mr Mohankumar,

        You recommended a 6V 4.5Ah rechargeable batter for this circuit. However, I am using a readily available Yuasa 4V, 4.2Ah rechargeable batter. Can this circuit still work or what changes should I do to make it work?

        Thanks for your help.

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    2. Ranjit Lahkar says: on September 12, 2010 at 3:42 pm

      this is d best project site

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    3. Bhavesh Lakhani says: on September 21, 2010 at 4:18 pm

      Dear Mr. D.Mohankumar,

      Can you please suggest me from which post I will get the battery protection circuits for dry lead acid for 6V & 12V batterys.

      Regards.
      Bhavesh.

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    4. Resp. Sir,
      Your circuits are very simple & useful, your work is much valuable for environment& for self employment.
      Sir , I need IC based High power LED driver with minimum components for driving 3 LEDs of 1 watt each in series from 12 volt battery, circuit should be buck-bust type. Please suggest, since I have to pay Rs.75/- for each driver. I am dealing with solar led street light business.

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    5. jerry fernandes says: on August 27, 2011 at 3:53 am

      Dear Sir,

      Thank you for your useful circuits.

      I need a economical led lamp circuit run on 3.2 Ni Cad or 3.7 lithium battery solar charged with light duration of at least 4-6 hours on full charge. Kindly help.

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    6. How can i indicate the relay’s NO and NC points

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    7. Hello,
      am making a solar led lantern for my undergraduate project.
      please,, can you help me with the simplest circuit diagram when am using a 1W solar panel.

      Thanks

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    8. hi
      can any say the cost of this project?

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    9. send 12v to 220v inverter circuit…

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    10. Alberto Perez says: on August 15, 2012 at 8:37 am
        member

      need price on simple solar light and
      other kits

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    11. ajish kuniyil says: on September 7, 2012 at 9:03 am

      dear friends…….i need a simple circuit design for controlling an electric motor by using a mobile phone,.

      thnkz

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    12. Hello Dears,
      Please Suggest me a circuit, with 6V Solar panel, 6V SLA Battery, 1W High power LED.
      With Battery full and drop Indicator.
      (Manually operated)
      Thank You.

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    13. Hi sir,

      I am planning to do a project based on the solar energy,which is to be used to light one single light for a shop on road side.does the circuit u have given enough is enough for this.I am studying my b.tech 2nd year.please suggest.

      Thank you.

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    14. Hi Sir,
      I would like to know the overall cost of this project.Also an alternative circuit using an IC.

      Thank you.

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    15. How can i construct a solar operated lamp?

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