Instructables

DIY solar rechargeable automatic night light (outside use)

Picture of DIY solar rechargeable automatic night light (outside use)

In this I will show you how to make a solar rechargeable automatic led night light. I made mine for outside use but hey you could do whatever with yours! :) 
 How did this idea come about? first I have been meaning to get some sort of light fixture in our back yard, I was going to install an outside light but that fell short once I saw the ratherr poor wiring in the garage. Now the light I wanted shouldnt be so bright but just enough light to see the table and surroundings so I decided to use leds, so I finaly came up with this product. Its a 2l bottle turned into a table light. but its more than that, Its solar rechargeable, and turns on by its own at night. I used a 3.7v lithium ion battery and a charge controller to properly charge the battery, an npn and a LDR circuit. now if you are not familiar with these types of batteries and how dangerous they can be then I recommend using normal batteries such as 4 double As, rechargeable of course. If you charge lithium ions inproperly it could end bad. That being said, do this at your own risk.
before starting give the video a watch :)
it lights at night and charges in the day time
 
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Step 1: Things needed.

npn switching transistor (2n3904)
10k resistor
LDR
5 white leds
5 volt power supply (needs to be rechargeable ((4xAA batteries should work just fine)) )
blocking diode 
2l bottle


If you change the value of the resistor you can alter the sensitivity of the on/off action. dont change the value by alot because you could fry the npn.
BurgersBytes7 months ago

You don't need the LDR, the solar panel can charge the battery and turn the circuit on. Use a PNP transistor so that when the solar panel voltage goes low, the transistor turns on. You'll also need to put a Shottkey diode to the battery so that it's voltage does not keep the PNP base high and keep the solar cell from draining any power.