LED project

Camaney

Hi, I have a Basic Stamp and I want to develop the following project:
Concentric circles (2 or 3) made of LEDS, that will start flashing at specific time (0 to 60 minutes).

I already made it for one LED, programming and components, but I need some help where to go to get more info as of how can I do it for many LEDS arranged in circles.

Can some one point me inthe right direction?
Thanks.

Mike Green

Nuts and Volts Column #6 talks about controlling high current (>20mA) or high voltage (>5V) loads with a Stamp.

The index is here: www.parallax.com/Resources/NutsVoltsColumns/tabid/272/Default.aspx

There's some other information in the StampWorks Manual.

www.parallax.com/StoreSearchResults/tabid/768/txtSearch/stampworks/List/0/SortField/4/ProductID/144/Default.aspx

You can put several LEDs in series with one resistor by using a high enough voltage (like 9-12V) and then parallel several LED / resistor strings switched by one transistor. Each red LED in a series string takes about 1.7V and the resistor has to absorb the rest of the supply voltage at around 20mA. You need to understand Ohm's Law to choose the proper resistor value (read the Wikipedia article on it).

Prettybird

Remember series current the same. About .6v drop / LED into 5v = 8 LEDs in series. Theory anyway. May need low ohm resistor and add or subtract a few LEDS.

Prettybird

· There is another trick. You can use a 74HC4017 decade counter chip and a 555 timer as a clock input. Crank up the speed ( frequency )·and use the reset pin to enable or disable the counter. Up to 10 LEDs can be used and never more then one comes on at one time. Make sure hoy have a big duity cycle ( relationship to on and off time) and your eye will never see the dofference. Only one series resistor from cathode to groung is needed. Good luck.· I always liked LED projects. Enclosed is the chip data sheet.