help with 1st LED setup

[lfcreds91]

i will be setting up my 1st LED base.....

this is how it looks.

the LED will be a 5mm spectrum or rainbow LED.......those that changes color every 0.5 sec.

battery will be 27 V, by joining 3 9V battery together.

resistor will be a 1/4 470 resistor.

the problem is i dont really know the LED forward voltage/current.

judging by the above setup, do you guys think its good to go?

or is it gonna BLOW!!!!!!!!!

 

[Mitale]

If you're worried then start with just 1 9V, then move to 2 9V, then 3. It may or may not even start with just 1 9V though.

 

[serious coinage]

Look at the information on driving LEDs in series here.

edit: after some quick calculations, assuming these LEDs are standard red ones with a voltage drop of ~2V and a current draw of 20mA, those resistors should be about 1K. You could run 2 470R resistors in series to get the right resistance if you don't want to buy more, but a 0.25W resistor is too small, you'll need 0.5W ones.

 

[nbw]

Do you really need the 27V? If you have 4 of those at 2V forward drop, that leaves 19V to get dropped across the resistors. You could probably get away with 2, maybe 1 if you're lucky. The resistors will need to change.

If you're using blue LEDs that run 2.9 - 3.5V, that's different of course - but 2 batteries should still be ok.