Solar Panel question

[Darth Homer]

A while back I had a calculator that was powered by a solar panel and I was wondering if any one has ever powered the lights in a model with solar panels. I'm planning too build a ship that will have a couple of panels and was thinking that since they will be there anyway I could make them functional.

[macfrank]

A while back I had a calculator that was powered by a solar panel and I was wondering if any one has ever powered the lights in a model with solar panels. I'm planning too build a ship that will have a couple of panels and was thinking that since they will be there anyway I could make them functional.

Those solar powered calculators use very little current - probably not more than 2 - 5ma when operating, and probably less.

A solar cell under a desk lamp will register some voltage, but it won't provide much current at all. You have to increase the surface area to collect more light. To figure out how much collecting area you'll need, you'll have to calculate the wattage per area available from your light source vs the efficiency of the solar panel. Don't be surprised if the size of a solar panel required to light one LED with the typical light levels available indoors is 1 ft. square or larger.

The solution is to get a solar powered battery charger that can charge up a battery over several hours in daytime, which can then be used to power the LEDs at night. You're still looking at a pretty big device. Here's a small but cheap example and here's a wider range of chargers

You could also build a more complicated lighting circuit to reduce current consumption. Use CMOS components throughout and minimizing the voltage/light level of the LEDs. You could also switch the LEDs at 100HZ or higher, with either a fixed 50% duty cycle or a variable duty cycle that would allow you to set the brightness.

Frank

[jwrjr]

Use the brightest leds you can get your hands on, and power them with as little current as you can (use larger resistors) to get the desired brightness. This technique is also useful for battery powered models.

[Lonnie Sweet]

I was thinking about this too and came up with solar powered LED yard lights. The little accent lights have a panel (kinda large unfortunately) and 2-AA batteries which charge during the day. If a person could switch the panel for a smaller one, (or put it on the base), it should work. A model that's lit without ever needing to be shut off.

[macfrank]

I was thinking about this too and came up with solar powered LED yard lights. The little accent lights have a panel (kinda large unfortunately) and 2-AA batteries which charge during the day. If a person could switch the panel for a smaller one, (or put it on the base), it should work. A model that's lit without ever needing to be shut off.

The solar panels on the accent lights are as big as they are because that's how much surface area you need to recharge two AA batteries in full sunlight If you put in a smaller panel it better be much, much more efficient. The amount of watts per square inch produced by indoor lighting is much less than direct sunlight, so even the accent light panels will not produce enough power to charge the batteries indoors.

I've used the accent light panels (and recharge circuits) to power a temperature/light level "weather" station" that I left out in the Mojave desert for 3 months.
The direct sunlight was more than enough to power the computer inside and charge up the batteries for nighttime operation, but it was a very low (a few ma) power CPU. Indoors, the panels just didn't have the surface area or efficiency to keep the batteries fully charged.