Make a Simple Solar Christmas Light

Inspired by this cute LED night light on Amazon.com(http://amzla.com/t4catdgl3rqt),

I decided to make a light-control Christmas light with my old light string.

It's so simple without battery protection function, but I don't care because I just use an old 18650 battery which is cheap.

Step 1:

So firstly, I designed this simple circuit.

On the left part, it's the charging module. The solar pad transforms sun light to electricity, via a diode that prevents reverse flow, the 18650 battery would be charged.

On the right part, the light sensor controls the voltage of Vbe(voltage between B and E). When Vbe>0.7, CE switchs on, then the light turns on. So when will Vbe>0.7? At night, the resistance of light sensor increases and the voltage of Vbe increases as well until the transistor "switch on".

Step 2:

Then it's something about handcraft.

Some tools I used, the lectric iron is the most important one.

Just place the parts on the board according to your preference.

Step 3:

Finally, connect the string lights and solar pad and test it.

When the circumstance is bright, it's off.

When I cover the light sensor with my finger, it's on.

Step 4:

Bravo!