Our event was six days and they had to endure the elements of mother nature. So, they didn’t look like a normal paper lantern that you see at every party, we draped complimentary colored fabric around the lantern. Then we coated the lanterns with fiberglass resin to make them more durable and aesthetically pleasing.
As for lighting the lanterns at night. We didn’t want to run wire through the 30-foot tree to power each lantern. Once installed we wouldn’t be able to reach the lights to turn them on and off during the event. The best store-bought solution was a LED battery-powered light that was designed to mount inside paper lanterns and the cost was $3.70 each. This didn’t quite fit our needs but did fit the budget. I also love hacking products I find.
To solve our problems we decided to use rechargeable batteries and attach a solar cell that would charge the batteries during the day. We created a small circuit that would use the solar cell as a switch. When the sun was shining the solar cell was active and would switch the power to the LED off and when the sun went down it would turn the light on. Much like the solar-powered driveway lights, you see at homes.
We had to twelve lanterns and I wanted to reuse the case, LED light array and switch. Here is the circuit and photos on how we completed the project. The key components are the PNP transistor that would act as a switch when it detected the change of current from the solar cell. And the directional diode that prevented the batteries from draining into the solar panel at night.
I put the few components in a perfboard near the solar cell.
We epoxied plastic drink bottle tops to the back of the solar cell. This covered the small circuit with some level of weatherproofing.
We could have improved the waterproofing by adding silicon to some of the holes.