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A Solar powered LED lantern

Charging under sunlight in a day

Using charged NiMH to lit up 1watt white SMD LED in the night or darkness environment

Photoresistor make the lantern only light up in the dark

Materials:
Transparent disposable drinking cup with lid
wire - to make hanger
wire - multicore 24G insulated (standard wire) for connection
NiMH Old also can, 1.2V 2Pcs with AA size battery case

Components:
Solar Cell 5V50mA or 3V50mA
NPN transistor in this project BC549C
Photoresistor
Resistor 1k
Diode IN4001
SMD LED 1W White

Tools:
Hot Glue Gun
Insulation tape
Soldering lead and solder
cutter


Instruction tips:
Solder the the circuit as in the picture.
Put the solar cell at the top outside the lid but make sure to cover all open terminal and circuit line to make it
rainproof or water proof. Make a hole for wire connection between solar cell and batteries. Make sure design are waterproof.
Put the photoresistor below the lid or whereareas the ambient can be detected. Put all together for example like in the picture.

Operation tips:
Put the lantern outside under direct sunlight in a day and the LED would not be lit on because photoresistor became less resistance under bright environment. The base would be more negative than decreased the current flow through LED. Meanwhile, the battery is charged.
When sunset or in dark the lantern would automatically lit on using battery power.

The charging cycles for NiMH is over 1000 times. Mine, using same technology has worked for one years. Just put it outside sunlight. When power blackout, it would be usefull as usefull as commercial solar lantern.
how do you prevent over charging?
this is simple system. 5V solar cell and 2AA NiMH batteries. The current is very low. (For me) Overcharge can be ignored. I also have used 2AA NiMH batteries with 6V 50mA solar cell and it has been run for 2 years above with no problem. Just limit the current to the LED because when the sun is too bright it can damage led. Mine, never death all 24x7.
very cool, do you have any idea what the current/voltage requirements of your led is?
~30 to 50 mA. Higher would burn if no heat sink

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