Simple Solar Day Lamp Which Lasts for 15 Years




Introduction: Simple Solar Day Lamp Which Lasts for 15 Years

All buildings have areas which are in darkness during day time. In such locations we can use a solar day lamp. The lamp will turn ON when the sun rises and will turn OFF when the sun sets. There are no switches to be turned on or off. It will convert the previously dark area into perpetually bright area through out the day.

The total cost of this lamp will be about 700 Indian rupees.

Step 1: Material Required for Making Solar Day Lamp

Material required:
You need following material (see figures)
1. Aluminum Channel
2. Wooden batten
3. Wood screws 0.5” long
4. Plastic or fiber washers 3 mm inner diameter
5. 5 White LEDs 1W rating
6. 3 Way terminal strip and mounting screw/nut.
7. Solar PV panel 12V 5 W
8. Wires

Step 2: Circuit Diagram of the Solar Day Lamp

The circuit diagram of a very simple day lamp is shown in the figure. It consists of a Photovoltaic (PV) panel of 12 Volts 5 Watt rating. The positive terminal of this panel is connected to a 15 ohms 2 watt resistor. The other end of this resistor is connected to the anode (+) terminal of LED1. The cathode (-) terminal of LED1 is connected to anode of LED2 etc. Thus 5 LEDs are connected in series as shown in the circuit diagram. The cathode terminal of LED5 is connected to the negative terminal of the PV panel.

Step 3: Aluminum Channel With €œT” Slots and Wooden Batten

Take an aluminum channel of 1” x 0.5” dimension as shown in the figure. It should have “T” slots cut. (Such channels are easily available in hardware shops). Cut this aluminum channel such that there are 5 “T” slots and one hole each at both the ends. Remove burr from edges and from “T” slots and clean the channel. Take a wooden batten of 10 mm X 10 mm size. Cut batten so that it’s length covers all 5 “T” slots and hole at one end as shown in figure.

Step 4: Marking the Wooden Batten (1)

Place the wooden batten centrally inside the channel and mark the holes.

Step 5: Marking the Wooden Batten (2)

Draw center lines for the marked holes. Also at a distance of 23 mm from center of each mark, draw a + sign.

Step 6: Drilling Holes in Wooden Batten

Drill 2 mm holes (10 nos) in the batten.

Step 7: Placement and Orientation of LEDs on the Aluminum Channel

Now mount the LEDs in each slot using the wooden screws and the plastic insulating washer as shown in the first figure. The orientation of each LED is shown in the second figure. If one LED “+” terminal is downwards, the “+” terminal of next LED should be upwards and so on. The aluminum channel provides support and also acts as a heat sink for the LEDs.

Step 8: Interconnecting All the LEDs and the Terminal Strip

Mount the 3 way terminal strip by using small screw, nut and washer in the last hole. Solder red wire from “+” terminal of LED1. Other end of red wire is connected to the first terminal of the terminal strip. Now solder a yellow wire from “-“ terminal of LED1 to the “+” terminal of LED2 and so on. Connect a green wire from the “-“ terminal of LED5 and connect it to the 3rd connector of the terminal strip.

Step 9: Interconnections Between the PV Panel and the Lamp

Insert 15 ohm resistor in the terminals 1 and 2 of the terminal strip as shown in the figures. Connect good quality red/black twin wire from the PV panel to the LED lamp. Red (+) wire should be connected to terminal no 2 and black (-) wire should be connected to terminal 3. The red/black wire should be long enough to run it from the roof to the place where you intend to install this lamp.

Step 10: Finished Day Lamp

Install the PV panel on the roof top or any other suitable location such that it receives sun light throughout the day. Run the wire to the room or place where you want to install the lamp. Place the lamp in such a way that nobody will be able to see the LEDs directly to avoid glare. If that is not possible then wrap the LED lamp in a semi-transparent plastic sheet. This will reduce the glare. Also, it will protect the LEDs from dust. Lastly keep the panel clean by wiping out the dust accumulated on it to get maximum light output.

Abhijeet Vijay Deshpande 
Renesas Mobile Corporation, Bangalore



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    21 Discussions

    What is the light intensity of the SMD LEDs you have used?

    1 reply

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

    dear bhvm could you please detail us the 1KW Solar setup with MPPT charge conroller(2x12v)

    1 reply

    Hello, I saw the comment today,

    1KW solar setup uses 6 PC 200w Solar panels.

    The Solar panels have a VOC of 44v, Two such panels are connected in series for VOC of about 90v. The MPPT Charge controller I used can take VOC upto 150v.

    Now, 3 such series sets are connected in parallel. Now effectively we have a 1200w Solar array with VOC about 90v

    The MPPT charge controller converts 90v to about 27v as required to charge 2x 12v Inverter batteries. In doing so, it reduces the voltage but boosts the amperes thats the beauty of MPPT. I am using systellar 4 stage MPPT that was custom ordered and can charge batteries with upto 40A as required.

    The Final output of this system is about 1KW as measured at the battery (accounting for voltage drop, Conversion losses, heat losses etc)

    dear bhvm could you please detail us the 1KW Solar setup with MPPT charge conroller(2x12v)

    Your Project is awesome.

    I am having something similar in my Basement since last 5 years. The LEDs are same as yours, However I am Using 1KW Solar setup to charge batteries with MPPT charge controller (2x12v) and I have designed LEDs to run on those batteries (24v) so I can use the lights Day or night.

    I just had a question, provided these are white leds, these have a forward voltage of 3 volt. So that adds up to 15 volt, which is more than the 12 volt delivers.

    Also, if theyare 1watt, they draw 333mA current. Over the 15 ohm resistor that means 5 volt drop.

    Add to that that the sun will not always be brihjt enough to have the pv deliver the full 12 volt.

    So how does this work? am i missing something?

    4 replies

    Dear diy_bloke

    Your 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 LEDs

    I hope I have clarified to your satisfaction.



    Please also have a look at this new article "High Power Solar Day Lamp" at following link.


    Dear Friend,

    where i can get solar panel in India - Ahmedabad ?
    can you help me please...

    2 replies


    You can contact Surana Ventures. They might send you to Ahmedabad by courier.

    Marketing Executive
    5th Floor, Surya Towers,
    Sardar Patel Road,
    Secunderabad-500003 (A.P.) India.
    Contact No.+ 91-40- 27845119, 44665799

    Pretty neat, 1 thing that i would recommend is to get a piece of plastic-wrap or film to put over the PV panel. Gives you rain protection and will keep dust from directly touching any circuit which could be fragile.

    nice instructables :D very usefull

    To enhance the utility of this day lamp following additions could be made to the basic circuit. It consists of two LED arrays, one PV panel and one two-way switch.

    1. Make two units of LED array and install them at two locations where light is required.
    2. Take a two-way switch. This has three terminals. Connect positive wire from PV panel to the middle terminal of two-way switch.
    3. Connect the remaining two terminals of the two-way switch to the respective resistors of each of the LED array.
    4. Connect the negative wire from the PV panel to the negative terminals of both LED arrays.
    5. Now you can turn ON any one of the LED arrays by using the two-way switch.

    (Abhijeet Deshpande)