LED trouble

[pollito14]

I was reading up on some old thread regarding LED and someone gave the idea of connecting 3 3.3V in series and then putting the bunches (clusters) in parallel.

I'm having trouble cause I did this and on the second cluster, the middle LED went from blue --> green and then really dim. I'm almost sure it burnt out. WHY? I don't want to have to solder a resistance to each and every single LED. Do I? What value?

These LED run at 20mA
Forward voltage 3.3V
Reverse voltage 5V

I've attached a picture showing how I connected the cluster that gave me trouble.

 

[1sty]

SHould be ok, although I would use 4 in series then parrellel. Also you may have just had a bad LED.

 

[pollito14]

You're probably right, 'cause when I replaced the middle one (the one that burned out) they all burnt out. But what's curious to me is this...

I have three in series at the end of the power line and the three that are giving me trouble are the second set installed (next closest to the power source). I can't use four at the end of the line, but I could use 4 at the second set. What if I were to install a 470ohm resistor in the last cluster?

 

[1sty]

Its just a 12 volt power source right?

 

[pollito14]

YUP! I've been testing everything before securing and reassembling and so I've been connecting straight to the 12V battery. Later on I will install a switch, that is if I fix this situation.

 

[1sty]

What king of aperage can these handle?
What is there resistance?

 

[pollito14]

I'm not sure what is their resistance but I know that they use 20mA

 

[1sty]

Well we need resistance to figure out what they are getting for amperage.

 

[pollito14]

I can't get a reading out of one. I have it in the resistance mode and nothing I put it in the diode mode and nothing

These are the specs that the seller gave me...

SPECIFICATIONS:
SOURCE MATERIAL:InGaN
EMITTING COLOUR:BLUE
LENS TYPE:WATER CLEAR
LUMINOUS INTENSITY-MCD:3000 TYPICAL/4000MAX
REVERSE VOLTAGE:5.0 V
DC FORWARD VOLTAGE:3.3V TYPICAL
DC FORWARD CURRENT:20mA
VIEWING ANGLE:?10?BR> LEAD SOLDERING TEMP:260oC for 5 seconds

 

[1sty]

What do you get for a reading? Is the DMM autoranging?

 

[pollito14]

Yes it's autoranging and it says OL (open line)

 

[1sty]

For all of them?

 

[pollito14]

YUP. I got another LED and the same thing

 

[1sty]

Measure that resistor you have laying around for s**** and giggles.

 

[pollito14]

My DMM is working and yes I know how to use it. It measures .467Kohms = 467ohms

 

[1sty]

I have no clue why it won't read the LED.

If the DMM is auto ranging why is it reading .467K ohms? Seems a bit weird.

 

[pollito14]

Yeah it's kinda weird but I honestly don't know why it does those things.

 

[1sty]

Where did you get the LEDs?

 

[pollito14]

EBAY Click there to see the auction

 

[1sty]

They should be 165 ohms each. What kind of markings do they have to make sure you have them connected the right way?