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I need to find a 7VAC LED(?)

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jasonbar:
Howdy-

I was doing some cabinet wiring today & busted the lead off an LED right where it enters the plastic package.  :[  Unrepairable.

It's the power/surge indicator on my power strip.  It's poking through my front panel by my main power switch.

I tried a direct swap of some other LEDs that I had.  They all displayed reeeeally dim.  Confused, I put my multimeter on it & couldn't get a DC voltage reading.  So, I switched my multimeter to AC & got a solid 7V reading.

I'd never come across an AC LED before.

A quick search on Digikey doesn't seem to offer AC vs. DC in their pull-down menus to filter through their LEDs.


Got any ideas on how to replace this?  My backup plan is to pull 5VDC off of an unused drive power plug if I can't figure this out... :[

Thanks,
-Jason

protokatie:

--- Quote ---I'd never come across an AC LED before.
--- End quote ---

now I am scared. An LED is a type of diode, and a diode is by design a "one way valve" for electricity.. The only AC LEDs I have run across are LEDs that are dual colored (IE pass AC through them and you get yellow, otherwise it is red or green only [depending on polarity])

Are you sure it is an LED and not a very small bulb? Or maybe a dual LED with each LED crystal going the opposite way (ala a dual color one, except the same color each way)?

fjl:
Never heard of an LED that was made for AC voltage.
Maybe the original LED that broke worked on lower power which accomodated for the varying AC voltage that it got. Or maybe it wasn't an LED.

Perhaps you can build a rectifier to change the AC to DC and plug in the LED.

Fozzy The Bear:
Guys Guys Guys!!! Please!!!

All LED's work perfectly well on AC Voltages...... They light up when the AC cycle is positive and not when it goes negative. So effectively they flash at the rate of the AC cycle. One of the side effects of this is that the flashing is so fast that your eyes don't notice it and the other side effect is that they appear to the eye to be brighter than their rating.

What you actally need here is an LED Rated at 3.5V. Because you're only using half the AC Cycle to light it half of 7V = 3.5V   Find yourself one of those and it will work fine. The other thing is that it matters not a jot which way round you wire it. This is AC not polorised DC. It'll just use one half of the AC cycle or the other half, dependant on which way round you connect it.

Best Regards,
Julian (Fozzy The Bear)

whammoed:

--- Quote from: Fozzy The Bear on April 30, 2008, 06:06:07 am ---Guys Guys Guys!!! Please!!!

All LED's work perfectly well on AC Voltages......

--- End quote ---

I think that's a little misleading.  You can run LED's from AC if set up properly.  LED's are indeed diodes but I don't think they are really good at the diode part...just the light emitting part.

from wiki:

--- Quote ---Most LEDs have low reverse breakdown voltage ratings, so they will also be damaged by an applied reverse voltage of more than a few volts. Since some manufacturers don't follow the indicator standards above, if possible the data sheet should be consulted before hooking up the LED, or the LED may be tested in series with a resistor on a sufficiently low voltage supply to avoid the reverse breakdown. If it is desired to drive the LED directly from an AC supply of more than the reverse breakdown voltage then it may be protected by placing a diode (or another LED) in inverse parallel.


--- End quote ---

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