HOW DOES IT WORK?

If ­you have a yard and have ever thought about lighting it at night, then you have probably heard about solar yard lights.  As long as a location gets direct sunlight, you can put a light there and have light at night for several hrs.

These­ lights are extremely interesting because they are almost like mini-satellites. They generate and store their own power during the day and then release it at night. This is just like a satellite that stores solar energy while it is on the sunny side of the planet and then uses that energy when it's on the dark side.

A solar yard light uses standard solar cells in a very straightforward application. A single solar cell produces a maximum of 0.45 volts and a varying amount of current depending on the size of the cell and the amount of light striking the surface. In a typical yard light, therefore, you need 6 cells wired in series.  In this yard light, the six cells will produce 2.5 volts and a maximum of about 350 milliamps in full, bright sunlight.

The solar cells are wired directly to the battery through a diode (which prevents the battery's current from flowing back through the solar cell at night). The battery is a high powered AA NI-MH battery. A battery like this produces about 1.2 volts and can store a maximum of approximately 1000 milliamp-hours. During the day, the battery charges, reaching maximum charge except on shorter winter days or days when there is heavy overcast.

At night, the solar cells stop producing power. The photo resistor turns on the LED.  The controller board accepts power from the solar cell and battery, as well as input from the photo resistor. It has a three-transistor circuit that turns on the LED when the photo resistor indicates darkness.

LEDs draw about 45 milliamps with the battery producing about 1.23 volts (0.055 watts). It produces about half of the light that a candle would. The 1,000 mAh NI-MH battery, when fully charged, can operate the LED for about 6-8 hrs on this 4" x 8" light. The Premium 2,500 mAh will operate the LEDs up to 12-14 hrs on a full charge. 

Half of a candle's light is not very much, and if you have ever purchased one of these yard lights you know that it really is not enough to provide illumination. You use them more for marking a trail or pathway -- they are bright enough to see, but not really bright enough to illuminate the ground to any great degree. They help define borders, pathways, & stairways.  Use them in walkways, patios, driveways, pool deck, stairways & along garden paths.  Due to the lower output, bugs are not as attracted to them as they are to other outdoor lighting.