Solar Powered Lantern
This is a quick DIY electronics project I set for myself so I could brush up on my circuit design and some building techniques. I bought a couple copper lanterns off ebay and fitted them with a circuit similar to the outdoor solar lights you can buy for your yard. Much of the circuit design is based on one of the simple designs on Evil Mad Scientist. That’s a great page to get started with.
I modified the circuit so that the lanterns could operate indoors near a window. Most solar lights, including the one on Evil Mad Scientist, are designed to be kept outdoors. So the solar panel gets a lot more light than one that’s kept indoors. If you use a 3V solar panel to match up with the 2.4V battery, the panel needs to get direct sunlight to charge the battery, and the light will turn on well before it gets dark. I decided to use a 6V solar panel. This way it charges the battery with only indirect light through a window. One potential issue is that a 6V solar panel under direct sunlight could overcharge the 2.4V batteries. Though, I’ve been running this circuit for over a year without any problems.
Assembly is pretty straight forward. You can see how I built it in the montage video at the bottom of this post. If you want the light to run outside, you’ll need to take extra precautions for waterproofing.
Here’s the parts list:
- 6V Solar Cell (16-100ma is fine)
- 2x rechargeable AAA batteries and a battery holder
- 1N914 Diode
- 4K Ohm Resistor
- 50 Ohm Resistor
- On/Off Switch
- PNP 3906 Transistor
- 2x flickering LED’s
- a small circuit board for mounting components
Here’s a quick montage of how it was constructed: