AC operated Led does not glow with DC

Thread Starter

endlasuresh

Joined Feb 11, 2010
19
I tried to test with multi meter and even battery with battery few leds that are operated by AC earlier.
I have took few from led lights that are used for decoration in homes and none showed light. Does these leds are dead or how shall we test them?
The new leds which i bought from shop they are glowing with multimeter, but these are not.
 

dendad

Joined Feb 20, 2016
3,909
You really need to post a lot more info. There are quite a number of reasons as to why your test will not work.
It could be the battery was to low a voltage, as would the multimeter.
Or, they may now be dead if there was no current limiting resistor.
Or, they may be dead if the battery volts was too high and reversed......

Can you show a photo of the LEDs?
 

Thread Starter

endlasuresh

Joined Feb 11, 2010
19
You really need to post a lot more info. There are quite a number of reasons as to why your test will not work.
It could be the battery was to low a voltage, as would the multimeter.
Or, they may now be dead if there was no current limiting resistor.
Or, they may be dead if the battery volts was too high and reversed......

Can you show a photo of the LEDs?
These are the leds and have in more colors.
 

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Thread Starter

endlasuresh

Joined Feb 11, 2010
19
Test them with AC! They probably use the "capacitive dropper" circuit, and DC current won't flow through the capacitor.
I didn't get your reply but we see in mosquito bat 2 leds and the one which lites when connected ac.
I removed this led but it doesn't light with multimeter Or battery.
I attached the image.
 

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Thread Starter

endlasuresh

Joined Feb 11, 2010
19
The items shown in the photos in post #6 ARE INDEED filiment type lights, NOT LEDs. So there is no reason to try to re-use them.
How about the led which i showed in next post, even i tried to test with old chargers that had a led. These leds are not lighting with DC.
 

MisterBill2

Joined Jan 23, 2018
9,267
I see views of a green LD and possibly a yellow LED , both attached to a circuit board. Both require a forward bias voltage close to 2 volts. If an LED is still connected to an external circuit, that may affect the possibility of making it illuminate. AND of course the voltage and polarity must be correct. Most LEDs can be damaged by excessive reverse voltage above some fairly low value. OR the LEDs may have failed, or possibly have some insulating coating on the leads.
 
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