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Author Topic: AC Line voltage powered LEDs?  (Read 4234 times)

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drventure

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AC Line voltage powered LEDs?
« on: September 02, 2010, 09:44:49 pm »
I've got an old brass and marble lamp that I'm restoring (as a companion piece to the arqadium).

Anyway, I'm wanting to hook up a few flicker LED's under the marble bits to make them glow, but I'd rather not bother with a ton of dedicated circuitry.

One option is to pick up a 5v Power brick, but there's not a ton of space in the base for something like that AND the power plug to plug it into.

Anyone seen a wire-in 5v PS, or have some other ideas on how I might power the LED's with minimal circuitry off the normal AC line that runs into the lamp?

I'm really not wanting to actually build a circuit for it, because, well, this is LINE voltage and it's going in a +metal+ lamp. All I need is to get shocked by the dang thing. I've had enough of that kind of electricity!

I was also thinking, maybe those LED christmas lights? not sure how the circuit in them works.

DaOld Man

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Re: AC Line voltage powered LEDs?
« Reply #1 on: September 02, 2010, 11:00:44 pm »
You can use a regular led, just size the resistor to drop the voltage from 120 to 2 or 3.
But the led will flash at 30 times a second, so it may be dim, or flicker some.
You could glue two leds together and wire them in parallel, with opposite polarities, then they both will flash alternatively, wish should be close to a normal one.
They also make a led that shines in 3 colors, based on supply polarity. AC will make it shine in one color.
Just put heat shrink over all the bare wires and you wont have to worry about shock.

drventure

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Re: AC Line voltage powered LEDs?
« Reply #2 on: September 03, 2010, 12:06:17 am »
Interesting. Hadn't thought of that, but it makes sense.

Looks like I have a bit of breadboard experimentation to do...

Thanks!

DaOld Man

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Re: AC Line voltage powered LEDs?
« Reply #3 on: September 03, 2010, 10:03:46 am »
Rough calculation in my very spacey head says try a 5000 ohm resistor but it needs to be pretty hefty, maybe 2 or 3 watts.

BobA

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Re: AC Line voltage powered LEDs?
« Reply #4 on: September 03, 2010, 10:10:23 am »
This circuit may help you.

I think the single circuit with 2 leds is correct but the multiple leds should not have the vertical connection on each pair.   The LEDs should probably be in series with the resistor being recalculated for the change in voltage drop.


« Last Edit: September 03, 2010, 10:14:22 am by BobA »

gryhnd

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Re: AC Line voltage powered LEDs?
« Reply #5 on: September 03, 2010, 10:40:05 am »
How about scavenging the inline psu from a trashed set of LED lights. The ones I tossed recently had a pretty thin one. Maybe about 2" long, 3/4" around.
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HaRuMaN

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Re: AC Line voltage powered LEDs?
« Reply #6 on: September 03, 2010, 10:43:16 am »
Cue drventure's house catching fire in 3... 2... 1...

Ed_McCarron

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Re: AC Line voltage powered LEDs?
« Reply #7 on: September 03, 2010, 12:36:08 pm »
But wasn't it fun to think you won the lottery, just for a second there???

bkenobi

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Re: AC Line voltage powered LEDs?
« Reply #8 on: September 03, 2010, 12:50:09 pm »
They also have a 12v version for the same price.

http://www.dealextreme.com/details.dx/sku.44240

drventure

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Re: AC Line voltage powered LEDs?
« Reply #9 on: September 03, 2010, 07:26:39 pm »
@Ed and bkenobi

That's exactly what I was looking for. I have a few 5v bricks, but they're all too big to fit. Those units look like they'd fit quite nicely.

@Haruma
Dude, now that ain't funny  ;)

@gryhnd
I was thinking that same thing, but I don't have any lying around. However, seems like that cirrcuit that BobA posted is likely what's going on with those led xmas lights.

In the end, I picked up several of those ac->12v bricks to play with, they're cheap enough that even if they don't work for this, I can find something to do with em!

Thanks for all the pointers!

HaRuMaN

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Re: AC Line voltage powered LEDs?
« Reply #10 on: September 04, 2010, 01:19:14 pm »
My response was based on daoldman's advice, lol...  doesn't sound safe at all.

drventure

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Re: AC Line voltage powered LEDs?
« Reply #11 on: September 04, 2010, 02:33:30 pm »
Yeah, I'm more inclined to go with those little PS bricks that Ed and bkenobi pointed out.

That looks a lot safer. I can use standard twist nuts for the connections, as is typical for that kind of wiring.

Then, the thin wires for the leds only carry 12v.

Ed_McCarron

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Re: AC Line voltage powered LEDs?
« Reply #12 on: September 04, 2010, 03:13:28 pm »
Yeah, I'm more inclined to go with those little PS bricks that Ed and bkenobi pointed out.

That looks a lot safer. I can use standard twist nuts for the connections, as is typical for that kind of wiring.

Then, the thin wires for the leds only carry 12v.

You still may need to tweak things -- 330ma is heavy for small LEDs,  you might need a 1W or multiple LEDs, or some kind of limiting resistor still.  Theres probably a hack to adjust the current on the brick.
But wasn't it fun to think you won the lottery, just for a second there???

drventure

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Re: AC Line voltage powered LEDs?
« Reply #13 on: September 04, 2010, 04:06:46 pm »
Oh, I was planning on resistors for the LEDs, just like hooking em up to an LEDWiz. No worries there.

DaOld Man

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Re: AC Line voltage powered LEDs?
« Reply #14 on: September 05, 2010, 05:26:02 pm »
My response was based on daoldman's advice, lol...  doesn't sound safe at all.

It's very safe, if you do it right :)

Beley

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Re: AC Line voltage powered LEDs?
« Reply #15 on: September 05, 2010, 07:30:23 pm »
Yeah, I'm more inclined to go with those little PS bricks that Ed and bkenobi pointed out.

That looks a lot safer. I can use standard twist nuts for the connections, as is typical for that kind of wiring.

Then, the thin wires for the leds only carry 12v.
Oh, I was planning on resistors for the LEDs, just like hooking em up to an LEDWiz. No worries there.

The power supplies that were linked to above are constant current power supplies , if you put a resistor in line (same as led wiz etc) the led will still get 330/320mA, these power supplies will increase the output voltage until 330mA is flowing (or it reaches its max output voltage), ~5v or ~12v respectively.  What you need is a power supply like these ones but with a ~20mA output (or whatever your Leds are rated for. Or a normal power supply (ie constant voltage) and wire it up using the appropriate resistor.





drventure

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Re: AC Line voltage powered LEDs?
« Reply #16 on: September 05, 2010, 08:40:54 pm »
Yikes. Not good.

But then, if the voltage just maxes out at the listed voltage (say 12v) then if I put a limiting resistor in, then it becomes a constant voltage (12v) PS right?

Or did I just totally waste my money on those bricks?  :-\


bkenobi

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Re: AC Line voltage powered LEDs?
« Reply #17 on: September 06, 2010, 02:25:29 am »

EightBySix

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Re: AC Line voltage powered LEDs?
« Reply #18 on: September 06, 2010, 04:24:38 am »
Have you considered electroluminescent wire? It needs AC voltage to work and comes in a variety of voltages. You could get quite creative with it...

Beley

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Re: AC Line voltage powered LEDs?
« Reply #19 on: September 06, 2010, 01:46:23 pm »
....But then, if the voltage just maxes out at the listed voltage (say 12v) then if I put a limiting resistor in, then it becomes a constant voltage (12v) PS right?

Or did I just totally waste my money on those bricks?  :-\



In theory yes, in reality it will depend on how its built,  its quality and any built in protection. 

No protection -   It will keep increasing the voltage until it either reaches 330MA or burns out
some protection - will cap out at the max voltage and stay there <-- what you want
proper protection - will increase voltage until the max, then shut off, sensing overvoltage/open circuit


I would suggest buying one of thous tiny USB Charger that plug into the wall, they are usually just simple 5v powersupplys.  DX usally lets you changer your order if it hasent shipped yet

drventure

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Re: AC Line voltage powered LEDs?
« Reply #20 on: September 06, 2010, 03:08:04 pm »
@Eightbysix

Actually, I've played extensively with ELWire, See here

http://forum.arcadecontrols.com/index.php?topic=88515.msg954990#msg954990

Easier to work with than I thought, and with a small control circuit, you can control it just as if it was a normal LED, via an LEDWiz, which makes it OH so much more interesting!

@Beley

Yeah, I've been looking for something like that but space is pretty limited under the base plate of the lamp, that's why those little bricks were so appealing. I think I'm going to go ahead and get the, and just wire up a test circuit with some scratch LED's I have. I'm thinking it'll work just fine since I've got a current limiting resistor in place, but, we'll see.

I don't have enough info yet on the bricks to know the internals.

My circuits a little more complicated that a single LED anyway..

I've got 6 flicker LEDs, wired in 2 banks of 3, each bank wired in series with a 470ohm resistor in line (this according to an online LED calculator I've used in the past). The 470 is a bit high (it actually called for 330), but, I don't mind them being a little dimmer, and I tested that out up front, using a different supply, but everything worked just fine.

I guess I'll find out when I get the bricks!

Thanks

Beley

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Re: AC Line voltage powered LEDs?
« Reply #21 on: September 07, 2010, 09:11:58 pm »
What exactly is a flicker led anyway? is it like one of thous LED candles? can you post a link.

drventure

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Re: AC Line voltage powered LEDs?
« Reply #22 on: September 07, 2010, 10:08:42 pm »
Sorry, yes, it's the led out of those fake tea light LED candles.

They flicker by themselves, you basically just hook em up like a regular LED. Very cool effect to embed them into other stuff.

RoyalScam

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Re: AC Line voltage powered LEDs?
« Reply #23 on: September 07, 2010, 10:34:50 pm »
Just my .02;

@BobA
Quote
but the multiple leds should not have the vertical connection on each pair.

These are needed to protect the low inverse voltage of the LEDs as long as one led is conducting, the other in the antiparallel configuration will be spared.

Also a resistor with a value of at least 1 meg and a voltage rating of 250 to 350 volts(dependent on line voltage) should be placed across the ac line to discharge the capacitor in this circuit when power is removed.

But I gotta tell ya, this circuit kinda creeps me out.  I wouldn't even breadboard this without an isolation transformer, and I bet without one, it'd cause 120hz buzz in any audio circuits placed nearby.

Regards,
Scam

drventure

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Re: AC Line voltage powered LEDs?
« Reply #24 on: September 07, 2010, 10:52:58 pm »
Yeah, I have no problems working with 5 or 12v stuff, but 120v ac... I think I'll leave that to those more qualified that I and just buy a prebuilt power brick.

But that's good info. Thanks!

BobA

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Re: AC Line voltage powered LEDs?
« Reply #25 on: September 09, 2010, 10:21:51 pm »
Just my .02;

@BobA
Quote
but the multiple leds should not have the vertical connection on each pair.

These are needed to protect the low inverse voltage of the LEDs as long as one led is conducting, the other in the antiparallel configuration will be spared.

Also a resistor with a value of at least 1 meg and a voltage rating of 250 to 350 volts(dependent on line voltage) should be placed across the ac line to discharge the capacitor in this circuit when power is removed.

But I gotta tell ya, this circuit kinda creeps me out.  I wouldn't even breadboard this without an isolation transformer, and I bet without one, it'd cause 120hz buzz in any audio circuits placed nearby.

Regards,
Scam

Wow learn something new every day.   It does look creepy the way it was drawn so I will not be trying it any time soon because I cannot see clearly how it works.

BobA

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Re: AC Line voltage powered LEDs?
« Reply #26 on: September 11, 2010, 06:28:19 pm »
Sorry, yes, it's the led out of those fake tea light LED candles.

They flicker by themselves, you basically just hook em up like a regular LED. Very cool effect to embed them into other stuff.

Since these were orignally using batteries, have you thought about wireing up some batteries?
AA batteries have about 10x to 40x the capacity of the coin/button cells that these lights usall come with.

drventure

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Re: AC Line voltage powered LEDs?
« Reply #27 on: September 11, 2010, 07:50:11 pm »
Yeah, actually, I had originally considered that, but I wanted them to come on only when the light was on. Otherwise, i'd have to have a second switch somewhere, which wouldn't be tough, but. Well, I guess I'm just being picky  :)

Plus I already have one of those "touch sensor" dimmer gizmo's (i'd bought for my arcade cab but didn't/couldn't use it) so I thought I'd wire that in to make it a touch lamp too.