HELP ON LEDS

[xSLICKVICx]

hi i recently ordered blue, red, green, and yellow leds from a site but when i try to power a single one on using a AA battery it doesnt work. Is it the leds or is it that im doing something wrong?
Thanks

[802Chives]

You are doing something wrong, that is not knowing how to properly run and LED.  Read an LED tutorial so you know what you need to do, hooking an LED to straight power source may work in some cases, however if you want to protect your LEDs you will need a RESISTOR.  There are plenty of LED calculators on google searches, so look em up.

Not really trying to be a jerk here, it is just extremely dangerous to play with electricity without an appreciation for the unexpected.  Granted it is hard to hurt yourself with a AA battery, it is easy to hurt yourself with a 200W 360 PSU, not to mention risk of fire.

In order to light those LEDs up it will take 2AA bateries in series for the red and yellow LEDs, and probly 3AA in series in order to light up the blue and Green LEDs.  In the case of AA batteries you can probly just hook them straight up without a resistor if you are just briefly testing, because the internal resistance of the batteries is high enough, it wont allow for them to draw an excessive amount of current.  However you will still be drawing too much current for the LEDs to last for their whole expected lifetime.

Please in the future research what you are doing, it is more of a safety issue than anything else

[xSLICKVICx]

hi i did reasearch about leds on instructables - leds for beginners and he showed how to light em up. I guess they were wrong. Thanks for giving me some tips i will try it out tonight and see if it works.

[802Chives]

Ah man instructables isn't the best place for info like that, there is a lot of misinformation floating around in there, and no one to correct it all.  using a AA battery may work for lighting a Red LED, since battery voltage is 1.5V and LED Forward voltage is probably somewhere near that.

As a General rule you always need to exceed the LED forward Voltage (Vf) with your supply voltage.  Different color LEDs all have different Vf so will require different circuits (diff resistors).  So you will need to know the specifications for all the LEDs in advance to do it right.

google LED resistor calculator for calculators that do the math for you.

sorry if my previous post was a bit harsh, it was more of a stern warning to other people who read it and are thinking of trying some LED mods by simply applying positive lead to positive and negative lead to negative.

[xSLICKVICx]

no problem i understand why yoou said that and yes i will try googeling thanks again ill tell you how it goes

[xSLICKVICx]

Ok i powered it up using 2 AA batterys as the power source and it lit up except the red 1s one red led burned out i figured i need a resistor for it. Thanks for helping me out 802Chives

[802Chives]

no problem, that is why we are here.  Yeah you should have a resistor for every string of LEDs no matter what you are using to drive them.  The blown red LED is why, even a AA battery can damage them.(kinda surprises me in a way, but not really)


BTW if you use a lot of LEDs and want to make an array, google LED ARRAY CALCULATOR, I think the first one that comes up is the best.

Good Luck with you Modding