RGB Spiral

I am working in a installation, for a museum, I had a plexiglass spiral that I desing , loos beutifull just as is, but some Leds will make more interesting so I drilll holes and hot glue leds ( at age of the spiral) and I am debating to use a Ping sensor or a Photoresistor, any way. the default state of the spiral is red light dimming like a hart beat. and sensor triggers colors mixing ( I am using RGB Leds) the arduino only has 6 pwm channes = 2 rgb leds, so by connecting the leds in parallel I am expanding to 6 rgbs, and is working nice.

what do yo guys think ...

thanks guys for all your help = got love open source

Can't see it so can't comment.

How about some photos or videos?

If your RGB LEDs are common anode, I'd use a ULN2003 to drive them: cheap and easy, with minimal soldering.

If getting hold of a ULN2003 is difficult where you live, there are lots of examples on arduino.cc of using a transistor to boost the output power of a digital pin.

And do post those pictures (or videos, once you get the whole thing running): it sounds like it'll look really cool.


I will make a vid and put it on vimeo, then link it from there so far is just the experimentalversion

video comming up. I can not find ULN2003 in my area, any of you have an extra one. or what kind of transitor can I use ...

Ok . video is here

only running 4 rgb out of 6 and yes that is my messy studio also a view of the wiring management ( thanks to my Mother)


Thanks for the video: that is cool-looking.

Assuming they're common-anode LEDs (I.e., the common pin is connected to the positive supply), you can use any old NPN transistor. Sample schematic here. Note that the LEDs turn on when the pin goes high.


actually they are not common-anode each (+) side goes to pin they have a common (-)

common cathode....

Yeah thanks for posting it in this section, I knew that you would get interest, unfortunately I cannot view your video (my issues, not the video) at the moment or I would comment...

Common cathode RGB LEDs are my prefered type because they can make coding simper but seem somewhat unusual in the world now, not sure why...


actually they are not common-anode each (+) side goes to pin they have a common (-)

In that case you'll want to use PNP transistors to do the switching. There's a page with lots of info about using transistors with logic circuits here.

You'll still need current-limiting resistors, even though the sample PNP circuit on that page doesn't show them.

mowcius: common-anode LEDs are popular because it's usually easier to add an NPN transistor, and switch the ground side of the load. Especially if, e.g., you're switching a string of LEDs for a tall 7-segment display, and the positive supply is > 5V.


Oh ok… I haven’t really done much with RGB LEDs I have only used them a couple of times…


Nice installation.


you could use the udn2981 for expanding your rgb leds