I Need Help Finding The Right Electronic Component.

You might search for "voltage sensitive relays" or similar terms.

FETs use virually no current to hold them on or off and have very low on resistance and will switch at logic levels.

Right,

A component that can do exactly that is a depletion mode Mosfet like BSP149, but are rarely used types and not always easy to get. S.M.

As previously posted, FET and MOSFET transistors are good to consider.

At a hobby level http://www.digikey.com and http://www.mouser.com are two good sources to consider. There are many more.

You should probably Google "FET Transistor Tutorial" and "MOSFET Transistor Tutorial". As you learn a little you will have more/different terms to Google. You should get sample circuits in one of your first few Google hits.

All transistors and ICs in Digikey, Mouser and others have datasheets easily available. The manufacturer's web site will have data sheets, probably Application Notes (App Notes) and possibly even downloadable software or "web workbenches".

Three last bits of wisdom:

First, you can not expose your transistors to high voltage. Google ESD.

Second, when a data sheet states "maximum" it means never go there. Always design to stay well under maximum (possibly never more than 25% of maximum).

Third, Google "Bob Pease" and "Jim Williams". They were both great authors that wrote many articles, Application Notes and books to help people both get started and get better at electronics.

When you have a home project electronics can be a lot of fun. Do a little work, learn something and when you are done you will feel good about it. Have fun.

Good advice.

Sadly the two gentlemen you mentioned have died this year, Jim first and Bob in a car accident while attending Jim's funeral.....poetic in a way.....

I'd use a common P-Channel MOSFET. See the simplified circuit sketch below for use in your application.

Thank all of you for taking the time to respond to my post. You guys are really great.

I think I have everything I need now to build this simple circuit and the lessons learned will be applied to other more advanced projects.

Thanks again.

Gavilan

you can get a simple transitor that will turn off your leds. it will be a transitir that when a voltage is applied it will stop a current.

I want to thank everyone for their help. Here is what I came up with as the best solution.

The P Channel Mosfet is a normally closed switch in this application. When the gate is energized it turns off the lights. The left terminal is the Gate, the center terminal is the drain, and the right terminal is the source.

Here is the circuit I use with a 6 volt supply. The R1 value is 100K. I bought the photo cell and PChannel Mosfet from digikey. The LEDs are mounted in 1/2 PVC end caps, 45 degree connectors, to a tee. This allows the lights to be pointable in both the verticle and horizonal axis. I run my power line (2-18 Thermostate Wire) through 1/2 inch plastic conduit. This circuit can also be used with a solar panel charged battery as the source. I also put a switch on the positive lead so I can turn the ligths off if I want them off for some reason. In the morining when light strikes the PC it energizes the gate and the lights turn off. In a solar application this circuit is fed from the battery.

On the original solar circuit I used a lead from the positive terminal of the solar panel to energize the gate but I like the photo cell method better.

This same circuit can be adapted to 3, 6, 9, 12, , , supplies by adding LED's in series. In this 6 volt circuit there are two LED's in series in each assembly.

This makes a very eye friendly, sky friendly, low voltage safe path way, dock, portch, steps, lighting system. Using super bright LED's from Allelectronics.com I have build four lighting systems, one solar and three plug in. The lighting is adaquate to see the path yet you can still see the stars. The neighbors love theirs and they draw somewhere around 5 watts and light a pretty big area about 60 to 100 feet in lenght.

The most efficient LED's are the Blue and White. The Green are pretty bright but draw considerably more power. The super bright Reds use the most power. Again, LED's from All Electonics; and P Channel Mosfet and 10 Lux Photo Cell from Digikey.

Again very eye friendly and sky friendly system.

Thanks for all your help.

Gavilan

I almost forgot - Special Thanks to mjb1962853 in post number 6 showing the basic P Channel Mosfet application circuit.