Variable Multicolour LEDs ...

[Torchy]

Buying some of these on ebay.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&category=50423&item=5707143990

Each colour led die has its own independant anode ...



The idea is, use a dual gang pot for gain on my 808 clone, top pot is the gain control and the second pot drives the LED shades from blue through to red ... sort of a visual indication of how "hot" the output is. Might take some working out though ...

[lightningfingers]

They look cool :mrgreen:

how are you planning on doing it with a dual ganged pot? If each colour has its own anode would'nt you need more than two pots stacked :? hmm this is going to me a headache now....
let us know how you work it out

good luck

[Torchy]

Thinking about using the pot second-gang as a voltage divider feeding an LM3914/3915 type chip with . Gives a bargraph output depending on the input voltage. Ten stepped outputs from the 3914 gives me either 3 per colour die, or use them as muliplexers for varying voltage supply to the individual dies via a transistor array chip ...

Dammit this is going to keep me AWAKE ...

[Joe Davisson]

This works with that sort of LED to cycle automagically through all the hues. (Shown as a pedal bypass indicator, but the 1k resistors can just go to +9v instead of the control transistor at the top for other uses.) More stages are possible in odd-numbers (5, 7, etc) for other effects.

http://www.analogalchemy.com/pedals/rgbcycler.gif

-Joe

[Torchy]

Dont want to cycle the LEDs, want to change colour according to an input voltage ramp ... sort of ... checking out pwm circuits using threshold triggers. Just ordered some MAX6964 samples ...

I aint going to get much sleep  :roll:

[Peter Snowberg]

I would try using a couple of small transistors like a 2N3904 and a 2N3906 to create a variable current source and an inverted variable current source. It would take some fiddling with the resistor values and I'm sure they will end up being specific to the transistors used, but you should be able to fade one out as the other fades in over the input voltage range.

I really like the blue<->red hot<->cold indication!

Take care,
-Peter

[aaronkessman]

did this ever work out?