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Flashing LEDs - resistor or not resistor?

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Chippie

Member
There is insufficient information to make a reasonable judgement..........

What voltage flashing led ?

what supply volts are being used ?
 

bogdanfirst

New Member
well you definetly need a series resistor....
dont think i know circuits where you don't need a current limmiting resistor.....
i am sure you need one. maybe a schematic could do?
 

Gene

New Member
The only flashing LED I know of (i.e., running without an external circuit) is a 2.2 volt model with a peak of 4 volts. If you connect this to a 9 volt battery without a limiting resistor, it will flash only once.
 

bogdanfirst

New Member
yes, the flasher is in the led, so the limiting resistors and all you need.
and ill say it one more thing...how often don't we use a limiting resistor?
 

kinjalgp

Active Member
If the duty cycle of the flaher is low, you can also do without the limiting resistor. But this is not at all a good idea. You should always use one to ensure long life of LED.
 

grrr_arrghh

New Member
OK, thanks everyone.

I am using a current limiting resistor anyway, and to answer your question bogdanfirst, how often don't we use a limiting resistor? - once!!
 

mechie

New Member
Constant Current ?

Hi Guys..
Just thought I'd chuck my two penneth worth in..
The flashing LEDs I have (the only ones I can get) are happy with 3.5v to 13v. NO RESISTOR.
The internal circuitry contains both the flasher and a current limiter circuit so the resistor is not required up to 13v.
 

grrr_arrghh

New Member
mechie, they sound alot like my flashing L.E.Ds

Mine work with or without resistors, but if you connect them straight to a 9v PP3 battery, they 'pulse', rather than flash!

I have changed my circuit completely and am now using a 555 in astable mode, and a small 12v bulb.

Thanks for the help everyone

grrr_arrghh
 
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