To all the Electrotechies: LED Voltage/Resistance

[thespud]

hhmm... Not sure if this should go here or in o/t or what, but im sure the mods can move it wherever it fits best.

Does anyone know the Voltage/resistances for a tri-colour LED (R,G,B)? I am just thinking about changing the dull, boring red LED of my alarm system to cycle through the RGB of a tri-colour.

[Pineapple]

Mine need 4.5V.
Easy way is use a 5k pot in series with 12V source. Turn it until the LED got brightess, turn it back so it just dim abit. Measure voltage across LED and resistance on the pot. Acturally you should measure current.

[WortownSolara]

just replacing it with an led is not going to allow a tri color to cycle through the 3 different colors. You would need some sort of board to get it to cycle. hmmm directed makes a piece called a 629R Which is thier scanning led assembly, you simply cut off the leads to the 5 leds they have, use 3 of the positives, then obviously the led itself is common ground. definatly would be different, i know thats the best way to get multiple led flash

[da_horse]

Spud, head down to Jaycar, get one of their RGB LEDS, measure ur current led voltage drop, calculate the resistance required and buy the corresponding Resistor.

Formula is :
.................. V(circuit) - V(LED)
R (ohms) = ----------------------
.................. I (LED)

assume that the car will always have 12V, and the Jaycar LED i'm looking at is CAT: ZD-0246 5mm RGB waterclear lens LED($5.95) , has a peak A of .1A and a max V of 2.6V then it would be

.................. V(circuit) 12 - V(LED) 2.6
R (ohms) = ------------------------------
.................. I (LED) .1
............. = 94 Ohm resistor

wire up the LED like so:

(+) ------[Resistor]----------(LED)--------- (-)

Jaycar doesnt have a 94 Ohms resistor so what u can do is try and see if a 100Ohm will work (Cat no. RR-0548) which may work but be a bit dim(dont think u can tell, V=12.6) or use a 91Ohm Resistor (Cat no. RR-0547), which should be ok as well (V =11.7)

The nearest Jaycar shop in perth, well the only one is in northbridge ( 326 Newcastle St 6003) so if u cant get to it, tell me what u want to do and if u want i can just send u the stuff cos i'm pretty close to a Jaycar store....


ok physics lesson has ended

[Pineapple]

There are self cycle 7 color LEDs. That's the one I'm talking about.

[da_horse]

this is what i meant...it cycles thru Red Green and Blue and only needs a single cathode and anode connection...

Tri Colour LED

[thespud]

I know i need a control box, but i also know that the tri-colours need a certain resistance/voltage at Red (highest Voltage & lowest Resistance) then blue, then green (lowest voltage, highest resistance).

What i am actually trying to do is get it so when the immobiliser light flashes, the first will be red, the next blue, then green, then back to red. Just thought it would be something different. I know i am going to need a 555 or similar to make it work too.