Posted: 10:07pm 24 Feb 2006

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Sorry folks that I wasn't clear enough on my last post.  My 12v garden lights are set to go. What I can't find is a photocell to turn the lights on and off.  I figured these things would be cheap.  I bought one at Home Depot for a few bucks but it doesn't work.  The package doesn't say it, but I think it is for 110v.  I didn't realize one for a 12v 3 w system would be so hard to find. 

I even looked at automotive sites. Didn't old Caddies have a photocell to turn on the headlights.

Radio shack doesn't list one one line, nor does any other company I've found.

Thanks again.

Ken

Posted: 11:00pm 24 Feb 2006

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Ah, I know exactly what you want. OK, first up, have you any expierence in electronics or putting together circuit boards?

To do what you want you could use a tiny solar cell, say from a dead solar powered calculator, or a LDR ( Light Dependant Resistor ). But you will need to put together a circuit using a comparator, like a 741 op amp or a NE555 timer chip. The chip will compare the value from the LDR or solar cell, to a fixed value ( a resistor or trimpot ). When it gets dark, the chip will drive a small relay or transistor to switch on the lights.

Another way is to buy a cheap solar garden light. These  have a solar cell to charge a couple of nicad batteries, and a small circuit with a couple of transistors to switch on the LEN light when it gets dark. You could modify this circuit to drive a small power transistor or MOSFET, and use this to drive your lights.

Glenn