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Rapid Pulse LED Program Answered

Hi there! I have successfully been making some LED hula-hoops but my ultimate challenge lies before me: I want to program colour-changing LEDs so that they pulse ultra-fast and appear 'white' when at standstill but leave rainbow trails when they move. I believe it to be an optical illusion caused by the pulsing... I assume this requires a PIC program but I have no idea where to start or even if I am on the right track - does anyone out there know how I might achieve this? thanking you in advance, Amelia


any picture of this LED hula-hoops,I'd like to see it many thanks

Hmmm...not sure why that's not showing up...

hey man this is what you are looking for...except i made over 30 modes and you can speed up and slow down the frequency...they will be available to buy soon http://www.youtube.com/watch?v=73msoGYatPA http://www.youtube.com/watch?v=gScuyumkQy8&feature=related http://www.youtube.com/watch?v=RyEY_xHC6ao&feature=related http://www.youtube.com/watch?v=73msoGYatPA&feature=related

Here is a simple circuit using a PIC10F200. This is a low cost chip (38 cents / qty 100) that can be programmed with the PicKit 2 ($35).

The on time can be easily changed from 1 to 255 milliseconds by editing line 43 of the source code.

Schematic (Can't attach image to this comment!)

Source code

That is a kit with the PicKit 2. The PicKit2 alone is here for a little less.

Are you in AU? The price is much higher than in the US

A single RGB LED can be used if it is common cathode. The circuit and firmware could easily be modified for common anode if needed.

You could also try a color changing RGB LED. It is too slow to appear white, by may look good in motion.

You could use a PIC (I'm an AVR man, myself), or you could just steer clear of the whole situation and use 3 555 (or similar chip, or use the quad 555 chip, the 558) to drive a few transistors to drive the whole thing. Or, take a look at goodhart's forum about his led scanner thing, if he got that working, that would be a discrete way of doing it.

Thanks for your reply, I should probably have mentioned that I am a complete ignoramus when it comes to electronics. I taught myself to solder and read wiring diagrams just to make the basic LED hoop. :) Would it work do you think to speed up a colour-changing LED so that it pulses so fast that it appears white? You sound like you know what you're talking about (particularly with your correct use of 'discrete')! I will seek out goodhart's scanner thing...thanks

I can create you a schematic of something that should work soon, probably tomorow... I'm studying for finals right now (that's right, we still have school while everyone else got out like a week ago, snow days seemed like a good thing at the time...), but tomorow is our last day of school, so after that I'll draw one up for you. Basically I'll make it so that you can adjust the speed in which the different colors flash

My goodness guyfrom7up, that's such a kind offer!
Take your time obviously, finish your exams, have a holiday, get around to it if it still interests you. I just finished what you guys call grad-school so I am sensitive to the needs of overworked students!
If you can just work out how to make a Red-Green-Blue LED pulse super-fast (thus appearing white), that would be the ticket.
It doesn't have to be adjustable or whatnot.
When you look at one of these hoops when not in motion it first appears as though the lights are white but on closer inspection, you can see that there are actually other colours flashing very fast. I hope that makes sense...
You can see an example under "Dragonfly" here:

actually, since it needs to entirley fit inside a hoop, i think a microcontroller with transistors would be way easier, cheaper, and less complex. If you want to use an AVR, I could write up a program for you, I wish I could say the same about a PIC. If you are going to use an AVR, may I recommend the attiny13a