I need to find a 7VAC LED(?)

[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]

I'd never come across an AC LED before.

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]

Guys Guys Guys!!! Please!!!

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

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:

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.

[Fozzy The Bear]

Guys Guys Guys!!! Please!!!

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

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.

A few years ago this was true..... But at AC 7V with a current limit on it, it's not going to hit breakdown. Modern ones work quite well now from the reverse breakdown point of view. To be honest you'd still be putting a current limit resistor in the circuit anyway and there probably already is one. Not to mention that this circuit he's attaching it to was already designed with exactly this application in mind and had an LED already on it. So it's unlikely to be any sort of a problem here.

Best Regards,
Julian (Fozzy The Bear)

[whammoed]

Granted, but you said "on AC Voltages" and not "on 7VAC in this case" or something similar.
Also I have noticed an issue with heat buildup when running directly on as little as 12VAC.  Heat will shorten the LED's lifespan.
I'm not disagreeing with you, just trying to keep someone from hooking up LEDs improperly to their mains power, etc...

[Fozzy The Bear]

Granted, but you said "on AC Voltages" and not "on 7VAC in this case" or something similar.
Also I have noticed an issue with heat buildup when running directly on as little as 12VAC.  Heat will shorten the LED's lifespan.
I'm not disagreeing with you, just trying to keep someone from hooking up LEDs improperly to their mains power, etc...

Oh! Agreed mate!..... It's just that I kind of assumed that what I'd said was in the context of exactly this application.  12V AC will indeed fry most LEDs But then the vast majority of LED's have a forward voltage rating well below that in any case. So unless it was someone who was a total dufus they wouldn't go connecting it to the full mains voltage anyway...  Mind you I do recall somebody connecting a 12V LED strip directly to the mains and then ranting on here at Randy Turner because the blue smoke fairy escaped from inside the little lights.

Best Regards,
Julian (Fozzy The Bear)

[whammoed]

Oh! Agreed mate!..... It's just that I kind of assumed that what I'd said was in the context of exactly this application.  12V AC will indeed fry most LEDs But then the vast majority of LED's have a forward voltage rating well below that in any case. So unless it was someone who was a total dufus they wouldn't go connecting it to the full mains voltage anyway...  Mind you I do recall somebody connecting a 12V LED strip directly to the mains and then ranting on here at Randy Turner because the blue smoke fairy escaped from inside the little lights.

Best Regards,
Julian (Fozzy The Bear)

I figured you might mean in that context, but I didn't think everyone would read it that way.
I get a lot of questions from customers that simply don't know anything about this sort of thing, so I've cime to realize there are a lot of people out there that are just starting to get a basic understanding of anything electronic...even people interested in BYOAC.

[fjl]

I still doubt its an LED. It will light up like the rest of you said but LEDs where not originally meant to be used on AC Voltages. AC will break down the component LED a lot quicker than DC voltage. So it's life span would be greatly reduced. So unless this was bad engineering, then perhaps they've come out with diodes that where made for AC.
 

Hey Jasonbar, how about a good close up pic of this LED?

[jasonbar]

I still doubt its an LED. It will light up like the rest of you said but LEDs where not originally meant to be used on AC Voltages. AC will break down the component LED a lot quicker than DC voltage. So it's life span would be greatly reduced. So unless this was bad engineering, then perhaps they've come out with diodes that where made for AC.
 

Hey Jasonbar, how about a good close up pic of this LED?

Hey, Efjayel-

Do you know how hard it is to take a good pic of an LED w/ an average point 'n' click digital camera?  :]  Not easy!  Well, just for you, my friend, I fished through 2 trash cans before I found the LED (in the bottom of the yuckier of the 2 trashcans).  I'm 99% sure that this is the LED in question and not the *other* one whose leg snapped off last night...grr...

Well, here are the 3 best pics I got.  I shrunk them a bit & messed w/ brightness & contrast to try to make the anode & cathode show a bit better.  It really really looks like an LED to me.  I can see that the 2 wire leads end in 2 pieces inside the LED, one shaped a bit like a "7" & the other more like an "i".  The red plastic package looks *just* like an LED, even with a small flat on the flange, aligned w/ 1 of the leads (indicating the negative lead).

Check it out.


Although this discussion has been cool & educational, I've decided to go w/ my plan B & use a crazy "disco" LED that cycles through all sorts of colors with all sort of frequencies & run it off my MAME PC's 5V disk drive power lines.  Now, where's the smiley for ducking flying objects chucked at me?  Oh, this is close enough:   

Thanks,
-Jason

[fjl]

Hmmm, that certainly looks like an LED. If I where you I would test it. Even though one of the legs broke off, I'm sure you can still make contact with the metal using a multimeter. I'd test it to see if it reads like a Diode then I'd put both DC and AC voltage through it to see how it reacts. Maybe when it broke, you accidently did something to the circuit board that caused it to output AC voltage instead of DC.

[jasonbar]

Howdy-

Boy, you're really getting into this discussion, Efjayel! 

I've got my workaround solution.  I'm going to let this sleeping dog...errr, LED lie.  I did try getting a probe onto the broken leg but couldn't seem to make contact.  When I broke the leg, the power strip was off, so I don't think I've damaged the circuit inside the power strip (I'm not going to open it up to check--it's already all mounted & captured & secured...).

Tell ya what, though.  If you send me your mailing address, I'll be happy to drop it in the mail (provided I can dig it out of the trash again...) & you can run all the experiments you want on it. 


Thanks,
-Jason

[whammoed]

I'm not sure why it would be hard to believe they would use AC to power the LED.  It takes fewer components to use AC...fewer components=cheaper...almost everything is made as cheaply as possible.

[Fozzy The Bear]

I'm not sure why it would be hard to believe they would use AC to power the LED.  It takes fewer components to use AC...fewer components=cheaper...almost everything is made as cheaply as possible.

I'd be more convinced if I thought he had a clue what he was talking about and deferred to people with actual experience of this stuff. I'm doing my best to be polite here.

Best Regards,
Julian (Fozzy The Bear)

[fjl]

Howdy-

Boy, you're really getting into this discussion, Efjayel! 

I've got my workaround solution.  I'm going to let this sleeping dog...errr, LED lie.  I did try getting a probe onto the broken leg but couldn't seem to make contact.  When I broke the leg, the power strip was off, so I don't think I've damaged the circuit inside the power strip (I'm not going to open it up to check--it's already all mounted & captured & secured...).

Tell ya what, though.  If you send me your mailing address, I'll be happy to drop it in the mail (provided I can dig it out of the trash again...) & you can run all the experiments you want on it. 


Thanks,
-Jason

I'll take you up on that. Check your PM's. And I've better not find any white powder in the envelope unless its something good. 

[Hoopz]

I'll take you up on that. Check your PM's. And I've better not find any white powder in the envelope unless its something good. 

If you did find any white powder on it, we know damn sure you wouldn't use the internet to search for an answer as history has shown that you haven't used a damn search buton....ever!

[jasonbar]

I'll take you up on that. Check your PM's.

Found it.  Will go out in tomorrow's mail.  99% sure that this is the correct LED.  I did bust another in almost the same fashion (broke off 1 leg where it entered the package) the same day...

-Jason

[DaOld Man]

Why dont you just take a cheap LED, hook it up, cover it with a cloth in case it de-materializes, and see what happens?
This worse it could do would be to fry the led. LEDs are cheap aren't they?

Disclaimer: Wear safety glasses while doing this. Be ready to unplug the frankenstein at a split seconds notice.
Never stare directly at the sun, and dont sniff unknown white powder, even if it is probably just foot powder (right?).

[fjl]

I'll take you up on that. Check your PM's. And I've better not find any white powder in the envelope unless its something good. 

If you did find any white powder on it, we know damn sure you wouldn't use the internet to search for an answer as history has shown that you haven't used a damn search buton....ever!

What's a search button? 

[Hoopz]

What's a search button? 

Same reason I've made some enemies here. I never intend to anger anyone but many people out there just don't like what I have say.

 

 

[fjl]

I like that saying, I should make it my signature! 

[fjl]

I got the LED today and tested it with my meter. It is indeed a regular DC voltage diode. Tommorrow when I get my hands on some of my other equipment I'll try it on AC voltage. And see how it fares out. But so far, I don't see why it was being run on AC voltage being a regular light emitting diode.

 

[Fozzy The Bear]

I don't see why it was being run on AC voltage being a regular light emitting diode.
 

Because it's in an AC power distro block you div!!!!  and there's no point in running circuits to convert it to DC, at more expense, when you don't need to.   If you'd listened to what people told you in the first place (me included) you wouldn't be wasting peoples time and pissing people off with it.

When you don't know what you're talking about it's best to keep your yapper shut.

As Groucho Marx said.... It's better to have people just think you're an idiot, than it is to open your mouth and remove all doubt.

Best Regards,
Julian (Fozzy The Bear)

[fjl]

What's a div?

[Fozzy The Bear]

What's a div?

Depends where you're from.... It means the same thing anyway:

1) Div is a scouse word for idiot. It is short for divvy which in turn is a corruption of Deva. The Deva Hospital was a well known mental hospital (since renamed the West Cheshire Hospital) on the outskirts of Chester. Chester was founded by the Romans who named it Deva.

2) originates from prison slang in the UK. A job often given to the lowest inmates was to put cardboard dividers into boxes. Someone given this job was a 'divider' or a 'div'. Now used as a nickname for those who display stupidity.

So now you know.....

Best Regards,
Julian (Fozzy The Bear)

[Stub]

Wow, we never lack for a detailed answer...