I am designing an LED Hula Hoop. I want to use 20 t-1 rgb leds.
It is 3/4in id tubing. I want them to chase or storbe with the push of a button. I also want a charge circuit.
I need advice on what chip and batteries to use and a code with which to program the chip in order to achieve these functions.
Any and all help would be appreciated!

Thanks.

 

Here are some ideas:
*Two rechargeable AA batteries.
*An inductive charger from an old rechargeable tooth brush.
*A boost converter to power the LEDs.
*4 interlaced strings of 5 LEDs each.
*A 555 & 4017 sequencer.

 

You could use the ATTiny13, or 15 to program various pulse sequences and skip the 555 and 4017....if you are capable of programming them.

Do they make Sub-AA batteries, because I don't see fitting a standard AA in a 3/4 curved tube, easily.

 

KJEAD, thanks for the idea for an inductive charger from an old tooth brush!! Excellent idea! I have a hula hoop that I bought because it was too much of a pain to make one myself (mounting and soldering all those LED's just took too long!) Changing the batteries is a pain. I found it was more worth my time to just go buy one. I don't suggest the cheap ones like this:
http://www.windycitynovelties.com/240543p/l-e-d-hula-hoop.html?s_cid=FRO240543
but I can't remember where I got mine at the moment.

I had originally found several DIY places to make the hula-hoops, like:
http://makeprojects.com/Project/LED-Hula-Hoop/300/1
http://www.instructables.com/id/LED-Hula-Hoop/

g2thefree, since you are looking for specific LED patterns in the hula-hoop, the regular solid LED's or even the "blinking LED's" won't work for you. But note that you will have to have a separate power wire go to each LED to control it separately. You can have one ground wire for the whole thing. That is 10 power wires in each direction for 180degrees (20 positive LED wires total). However, you specified that you wanted to use RGB LEDs, so you would have to multiply this by 3 - one for each color. (60 wires).

I totally agree with KJ6 that you would want to use a 555 timer circuit and hook it up to a decade counter (sequencer). I just went and looked this up (since I would have hooked this up to a decade counter with a decoder.... which is EXACTLY what the 4017 chip is -- both of these in one package!) Because you have three different colors, I would suggest three of these chips. Then you just use pin 13 to disable some of the colors that you don't want.

If you want to strobe them instead, you can hook them all up to another LED driver at the same time and have them all blink simultaneously. Maybe another 555 blinking here would do the trick.

To switch between these modes, I would suggest a hack. You can use a 7490 (or 7493) counter that has 4-bit binary output. After you debounce the switch, put it into the clock of this counter. Hook each of the first 3 binary outputs to the R/G/B enable pins. This will give you all the color combinations that are strobing around. Hook the 4th pin into the output of the 555 strobing pin. As you press the button, you'll cycle through the different modes of LEDs.

Have fun.