Led component will not illuminate when power source is applied

Mustin Jettam's picture

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Joined: Jan 18, 2021

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Led component will not illuminate when power source is applied
January 18, 2021 - 10:40am

As an experiment, and for my own education into electronics I am trying to light up one LED diode in my 60wLED bulb.  I have pulled the bulb apart, I have tested the bulb, and it still illuminates. Now, I am trying to test each of the 8 LED's. I have applied a variable 6-12V power source to the LED, yet it still won't illuminate. Can anyone suggest what I might be doing wrong?

I can confirm that the power source is putting out the correct voltage 7.5V and or 9V, because I checked it with a multimeter.

thumb_ledTest2.jpg

Sourav Gupta's picture

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Joined: Feb 12, 2018

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Possibly you fired the led. Typically the led start to glow from 1.5v to 2.2v. the voltage will increase the forward current. Going beyon 3 volt is not recommended without current limiting resistor.

Mustin Jettam's picture

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Joined: Jan 18, 2021

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All LED's are working, I checked them again by attaching the +- of the circuit to power, and they all illuminate.

Just to confirm; I should be able to make each led illuminate by sending a 2V current to the +- of the led diode, correct? 

I am not sure why they don't illuminate when I test them one by one like in the image. 

 ledTest2.jpg

Sourav Gupta's picture

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Joined: Feb 12, 2018

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This circuit uses a diode bridge. It is a transformerless AC to DC contruction. The LEDs are connected in such a way that the total series voltage is much higher to run on AC outlet voltage. You need to have higher voltage across the LED string to light them up.