wiring 5 red leds help

[darkkon]

hi im trying to connect 5 red leds to a resistor, but when i wire it up and connect power to it, it will not light up.


main power +12v
resistor 56 ohm 1/4th watt 5% tolerance
red led specs: 20ma, 2.2v

can someone please draw me a diagram on to how i should wire these together? i have tried a few different ones including these sites

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

http://www.theledlight.com/ledcircuits.html

any help would be appreciated. Thank you.

 

[Mr Happy]

If you can't make this work I think you are trying to go too far, too fast.

When you can't make something complicated work, start with something simpler and work up.

Use lower voltage power supply and try to make one LED light up. Get a 3 V supply using two 1.5 V alkaline batteries, use the same resistor, and one LED. Take note of which battery terminal is positive and which is negative. Try connecting the LED both ways round and see which way works. Make careful note of this because LEDs have positive and negative leads and you must connect them correctly.

When you have determined how to make one LED light on a three volt supply, then try making five LEDs work on the 12 V supply. Put all the LEDs (the right way round) in series with the resistor. If they are not damaged they should light up.

Note that if you have ever connected them the wrong way round to the 12 V battery they might have been damaged. Test each of them one by one with the 3 V battery and resistor to see which ones work and which ones do not.

 

[Robin24k]

Most 5mm LEDs have leads that are of different lengths to help differentiate between + and -. If yours are the same length, test them and cut the - one shorter so you can tell.

I generally test LEDs on an old CR2032 battery because I can just stick the battery between the leads. If you have one, that would be a bit more convenient than 2AA or 2AAA. Mine are old CMOS batteries and somewhat drained, so a resistor isn't necessary if the testing is fairly quick.

 

[darkkon]

i tried a different setup to be more organized.

http://img148.imageshack.us/img148/9797/photo0086i.jpg

http://img202.imageshack.us/img202/7239/photo0087e.jpg

the power is +12v
my leds are 2.2v, 20ma
resistor is 56 ohms 5% tolerance

i tried hooking them up with a 3v cmos battery or even two AA's with no avail. but i will reattempt it.

any help in the meantime on why my diagram above shouldnt work please tell me. i have no idea other than the leds are defective and i am going to replace a few good ones just to be sure, if one led doesnt work will it not run the circuit?

 

[Robin24k]

You need to resize your pic to be 800x600 or smaller. I would try to help you, but I can only see a wire or two on my screen without having to scroll. :candle:

 

[darkkon]

http://img148.imageshack.us/img148/9797/photo0086i.jpg

http://img202.imageshack.us/img202/7239/photo0087e.jpg

 

[alpg88]

should be very easy, 5 leds and resistor all in series, just make sure you get polarity right, it should work.

 

[darkkon]

as long as the polarity of the resistor doesnt matter (since only negative goes to it) then all the lights should light up, but none do. :\

 

[chongyixiong]

Well, what I believe is that one of the LEDs shorted out, maybe the first in the series.

You wanna try testing each LED (also ensuring correct polarity) before joining all 5 of them together?

Test all individual components then only stick them together.

Let me know if that works out.

Cheers.

 

[TorchBoy]

You know, chongyixiong, Mr Happy explained it better in post 2. And one of the LEDs may be burnt out (open circuit) not shorted.