Colour-changing LED problem

[philbinator1]

I got some LED's that change 5 or 7 colours, thinking "man that'll look cool, no-one i know has them" but when i installed it
in a pedal it would cycle once or twice and then die!     or just stay on one colour after a cycle.  does anyone know how to
remedy this?  do i need a 555 timer in there somehow?

[kurtlives]

Did you limit the current getting to the LED with a resistor?

[philbinator1]

Yup, 4.7K.  I think if i didn't the LED would blow, right?

[mantella]

I don't know why yours is doing that. But I took out a color changing LED from a cheapo halloween pumpkin light (which, btw was 99 cents for a pack of 6 of them. If you bought the LEDs separately at rat shack, you'd pay $2.99 each, plus another $4.99 each for the 3V lithium batteries. That comes out to $47.88!) and tried it in one of my pedals as a bypass indicator LED. It worked, and looked really cool, but caused a nasty cycling buzz/hum sound in the background. So, I had to go back to a regular one.

[composition4]

Does the LED have 3 leads rather than two? Just looking at a colour-changing LED datasheet from http://pdf1.alldatasheet.com/datasheet-pdf/view/184695/MICRO-ELECTRONICS/MSGBB557TA.html, the third terminal controls the mode - and it appears if left open, it only cycles on a one-shot after powerup.

If you do have 3 terminals and you haven't grounded the spare control terminal, try grounding it then powering up

Just a thought

Jonathan

[philbinator1]

yeah it's just a two-lead.  I'd like to try it with a 555 ic anyway...anyone got an easy blinking led project for a noob?   

[anchovie]

The idea with these colour-changing LEDs is that all of the control circuitry is contained within the package too, therefore there's no need for a 555 or anything like that.

I suspect that your resistor may be too large. 4.7K would be fine if you were using a single red LED and wanted a low draw on the battery. These colour-changers have red, green and blue LEDs in the package.

[philbinator1]

the leds i have, have more colours in them...maybe 5 or even 7 colours, from memory.  i might go test it now to refresh
the old memory   

[philbinator1]

The idea with these colour-changing LEDs is that all of the control circuitry is contained within the package too, therefore there's no need for a 555 or anything like that.

I suspect that your resistor may be too large. 4.7K would be fine if you were using a single red LED and wanted a low draw on the battery. These colour-changers have red, green and blue LEDs in the package.

I've just finished testing the led with different resistor values, starting at 4.7K , 3K, 2K, 1.5K.  on all these values the led wasn't functioning
as i thought it should, eg too dim, getting stuck on a colour, stuttering between colours etc.  Then 1.0K, 470R things started changing more
smoothly.  But at 330R, 270R and 220R the transisitons were smooth with good colour, perfect!  Anything under 100R and the colours were
too bright and started getting stuck on colours, and with no resistor (I was prepared to sacrifice it for testing) it was stuck on white and getting
very hot so i pulled the plug.    I ended up using 330R because the colour was the richest with good stability.

so yeah, you're theory was totally correct!  cool!      

[anchovie]

Glad it's working!

By the way, even though you have more than three colours there will only be red, green and blue diodes in there - the other colours will be created by mixing different levels of these primary colours.

[philbinator1]

yeah i thought so, i can see that the 'violet' is pretty much most blue with a little red.  cheats!