resistors

[toonarmy]

can anyone help me find the right level of resistor for my Ironman kit.It has 6 leds rated at 8000mcd(white)in parallel running of 2 AA batteries.The one in now is heating the battery pack up.Need to sort this out before finally assembly.
I was using one with brown/black/red/gold bands in that order.soldered to the + lead.Hope you can help(in laymans terms please)

[USS Atlantis]

To get the resistor value I need two things

Voltage of the LEDs
current draw of the LEDs

The one you're using is currently 1000ohm (1k)

Probably a little high, will dim the LED's but shouldn't heat the batteries unless you connected the LEDs backwards - but then then they wouldn't light up

HMMMM

[feek61]

The Wiz will tell you everything you need to know.

Look here:
http://led.linear1.org/led.wiz

[nickn]

Well, most LED's use about 3.2 volts..depends though.. Current draw is about 25ma..
so for a Single LED/Resistor,

12volt - 3.2volt = 8.8 / .025A (25ma) = ~350 Ohms (330)
9 volt - 3.2 = 5.8 / .025 A = ~232Ohms (220)

At anyrate, the wizard thing does all the math for you.. Forward Voltage is the 3.2 mentioned.. Diode foward current is the 25ma.. Wattage you want to pay attention too..Putting a 1/4 watt resistor where a 1 watt resistor should go results in a very very hot resistor.. which could easily burn up or catch fire.

[toonarmy]

Took the leds left over back to Maplins(our radio shack) and was told that the bag of 6 LEds i bought was a "lucky bag".All mixed voltage despite being all 8000mcd.There is no mention on the packet and they all look identical.How dumb is that.
I'm just going to install a push to close switch.so the lights only come on for a few seconds.
Thanks for the info guys.I'll know better next time