[SOLVED] LED blowing up all the time

[nicksydney]

Hi,

I know this suppose to be an easy solution but for some reason I can't get my head around it. I'm experimenting with simple LED with breadboard this is what I have.

1. Breadboard (solderless board)
2. 12v (6 x 1.5v) battery holder.
3. LED (this is the LED specification -> **broken link removed**)


I tried using resistor of 0.25w it blew up (both the LED and the resistor), next I tried resistor of 0.5w the LED glows a bit and then it dies off looks like it got burnt or something, next I tried 1W resistor it's the same like the
0.5w, I'm not sure what is wrong. Can anybody help me to point me in the right direction ?

Thanks

 

[varunme]

you have to use a resistor in series with the LED , the value of the resistor varies with the led colour , this is to reduce current in the circuit to protect LED , see below page
Resistor value calucations for LEDs

 

[hexreader]

6 x 1.5V does not give 12V.

What value of resistor are you using? (how many Ohms?)

220 Ohms (1 Watt) resistor will give maximum brightness at 50mA (but is pushing the LED to the limit)

470 Ohms (0.25 Watt, or to be cautious use 0.5 Watt) will give a comfortable 20mA.

EDIT: Ooops... varunme got there first

 

[varunme]

EDIT: Ooops... varunme got there first

hi hexreader , what was it ?

 

[nicksydney]

These are the 2 resistors that I mentioned in my previous thread the one with paper cover that says 'SOANAR' it says it's 1W while the other one it mentioned in the plastic it's 0.5W

 

[varunme]

nicksydney , its way too low
use a heigher ohm value

 

[nicksydney]

Hi varunme,

How do you read it to know that it's too low ? just want to learn how to do it

Thanks

 

[bigdogguru]

The color codes on a resistor indicate its value:

Graphical Resistor Calculator

Resistor color code calculator

My Resistor



I would recommend purchasing a pack of 470Ω 1/4 watt resistors which should give you the desire current limiting.

BigDog

 

[nicksydney]

Looks like after using one of BigDog's link I managed to calculate the Ω values which comes to - 10 and 15 which makes sense why the LED keep on blowing up. Need to go back to electronic shop to do more resistor shopping.

Thanks all

 

[ard]

Hi Nick, the pakage says 15 ohms; thats WAY too low! As per you LED specs, it drops 2 volts across itself; you have a supply of 9 volts. So, assuming you want to drive the LED at 20 ma, you need a resistor of around 470 ohms. The wattage of the resistor is fine; for these values even a 1/4 watt should do.

Regards,

Anand

 

[bigdogguru]

If you examine the two labels shown in the photos you provided, you will notice they indicate 10R and 15R which is equivalent to 10Ω and 15Ω, the use of R to represent ohms stems from the lack of the omega (Ω) character in some label fonts.

BigDog