I'm very interested in experimenting with solar power. I'd like to start by making a solar tracking system. I'm overwhelmed by the selection of light sensors available from online resources. Can someone point me to something that's available for online purchase preferably shipped from the US, that is reasonably priced and would be compatible with the processor included in the basic nerdkit?

Thanks a bunch!

Dale

I had the same dilemma some time back. I found the best way was to build it all from scratch. A simple comparator circuit and a couple of photo cells and a driver circuit is all you need.

Picture this: Two photocells, on a opposite sides of a wedge. If one has more light falling on it, it creates a differential between the two cells. Each cell feeds a comparator, which is essentially an OP amp set to infinite gain. A couple of them in a circuit can control a motor that moves the array until both photo cells equalize. They would be pointing in the direction where the light is strongest.

There are several variations on this that can be tried as well as a homing circuit to point the whole thing toward the East every morning.

Thanks Mongo, that's very similar to what I was thinking. Do you know what photocells to get?

Dale

Pretty much open on that one. Just as long as they are the same.

A good deal on CdS cells: http://www.goldmine-elec-products.com/prodinfo.asp?number=g14025 Ships from within the US, but there's a minimum $10 order. I usually get the surprise box, or a couple of the microchip assortments to round it out.

As an alternative, your local radio shack also probably carries them: http://www.radioshack.com/product/index.jsp?productId=2062590

I usually go to the nearest 99 cents/Dollar shop and look at the night lamp section. Sometimes they carry automatic night lamps with LEDs (that turn on when it is dark). Just remove the CdS light sensor from that. You can also salvage other parts from that night light. You can also do the same for Photocells just check the stationery section and pick $1 solar calculators and then remove the solar cell from that. This way there is no waiting time, no shipping, no minimum order to worry about and it is cheap. And I forgot about the most important thing - I feel very happy and satisfied when I take things apart.

-Raja

I did some more research and found out that you can use LEDs as light sensors. They generate up to 1.75 volts in sunlight, enough to trigger MOSFETS!

Thanks for the suggestions everyone.

Dale