need some basic Electrical engineering help

[joyride]

For my model Im building in class, I need to add some lighting. These are going to be a sort of beacon light. They dont need to be bright, and I think I can get away with a few LEDS. I need to illuminate two 4" X 3" areas of thermoformed plastic. Idealy, these would blink a little as well. Im asuming this should be fairly simple, and can get the parts at Radioshack.

Problem is, I am not familiar with the values needed, resistors, or how to make it flash. These also need to operate on a battery however I cant fit one of those big ass ones in there. A few 9v would work fine. Also, I can split up the two lighted areas so they run independantly of each other. If you guys gcould possibly help me out here, it would be appreciated.

[HoseHead]

Hack up Mom's string of LED Christmas lights .....

They're like $5.00 a string. A 9VDC battery should run a few of these all day long. Always have a fully charged spare battery during project marking!! Some do blink, but I'm not sure how this is accomplished with LED. Incandescent ones had a bi-metal strip that would heat up, then open, then cool down and close repetitively. LED's generate relatively no heat.

Or get a cheap set of solar powered garden LED lights. Then you can profess to be an environmentally conscious, tree hugging, cappucino sucking, anti nuke, peace love dove kinda guy too......

[Jacampb2]

Radio shack has a few blinking LEDs, this one, cat. #276-312 does not list what color it is, but it is the brightest blinking one they list. This one, cat. # 276-036 is cheaper, red, but significantly less bright. There is no special resistor needed, unless you intend to run them at a higher voltage than what they are rated for. RS is not the best for data sheets, but most LED's are 3Vdc. So, two AA series batteries. The second one I mention lists a typical voltage of 2.25Vdc, that is kind of weird, and to run it on 3Vdc, you would need somewhere around a 9 ohm series resistor to limit current, 1/4 watt dissipation should be fine. Match your power supply as closely to the LED's rated voltage as possible. Otherwise, the current limiting resistor is just throwing away the excess as heat. The first LED I listed will happily run on 3V w/ no current limiting resistor.

Good luck,
Jason

[Jacampb2]

Just found this link, and it may help you out. Online Calc for everything these days Input the basic specs for your led and it gives you the closes commercially available current limiting resistor. http://led.linear1.org/1led.wiz

Later,
Jason