Electronics > Beginners

Help identifying an LED. I think its a 3528 or a 2835

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TT_Vert:
I believe dimension wise they are the same correct?  is it just the efficiency that separates them?  Reason I ask is i have an LED light fixture that I want to swap the lights out for a cool white led.  I checked my my adjustable power supply and at 20mA it is around 8.2V which confuses me.  If it has multiple LEDS on one chip would it still only have 2 solder pads?  Is there any way to visually ID one that has multiple LEDS on the chip?  If it was 3 LEDS that means that each had an average Vf of 2.73V which seams low and if two, 4.1V sounds high.  Any input would be appreciated.  I always seem to get stumped by these things.  This particular light has 15 of these in series and has 120Vac rectified and 110Vdc is coming out to an 8 pin chip which I think is a constant current drive but the numbers don't come back to anything.  here is also an N channel mosfet in there.

Sorry for the basic question here.

Dave

mariush:
Make sure the LEDs are fully open, it could be that at 20mA, the led is still partially closed, so you see a lower voltage. May be 8.5v..9v at 50-100mA.

A led can have multiple diodes in series internally, so you'd get only two terminals. 

Besides opening one led to visually see the diodes, you could limit the current to a very low amount, like 1-5mA and use a microscope or some camera in macro mode to see each diode in the led light up (at a level that your eyes may not detect)

tooki:
I think 3528 vs 2835 means the contacts are on different sides.

TT_Vert:
I can not get them even close to 100mA.  I did gradually start to increase current w/ my power supply and i didn't really see multiple LEDS but I was looking w/ my naked eye. 

TT_Vert:
Can anyone else offer any insight?  I'd really like to swap in new LEDS but I'm not sure exactly what to replace these with given the apparent Vf.

Dave

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