[Hai-users] Sun sensor

[Byron Peebles]

Fascinating.  Thanks, George.

At 09:15 PM 5/9/2005, George Pontis wrote:

> >
> > I've read about solar cells being used for this, since their output voltage
> > varies by solar intensity.  Someone adapted one of those "put it on your
> > dashboard while you park at the airport" cheapies.
> >
>
>Output voltage is not a good indication once the light even starts getting
>bright enough to do any meaningful heating. If you really need something
>proportional to light you should measure the current of the cell when the
>output is shorted. A usable approximation would be to put a resistor across
>the cell that lowers the voltage to about half of what it is in bright sun
>with no load. For a single silicon cell that would be less than half a volt.
>Then you can just measure the voltage of the loaded cell and you will be
>able to tell how bright it really is.
>
>If you do go with the solar cell method, you might want a red filter over
>it. This will give you a better measurement of the heating power from the
>sun, which does not go down quite as much on an overcast day as does a white
>light measurement.