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
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
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 âTâ 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