What do I need to run LEDs with 110VAC?

T

twyztyr

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Jun 7, 2004
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I got 200 AOL CDs from work, so I figured I might as well put them to good use. I was thinking about making a pair of these using really bright LEDs instead of the flourescent tubes. I know that wiring them directly to a power cord is probably one of the dumbest things imaginable, but I was curious to know if I can make this work, and what do I need to do it?

I would like them to be functional and can actually be used to provide usable light in a room, so if anyone has any ideas or input, I'd appreciate it.
 
You can directly hook an LED upto 110VAC, provided you use the proper resistor to limit current. However, as you have identified this would be a little more dangerous then some other solutions.

I would recommend you just get a little 12v power brick and use that to drive your LEDs and resistor. That way all the dangerous voltages are contained in the power block itself.
 
Hooking up led's'to 120v is fine, have you ever seen the led chrismas lights? The only problem is they'll flicker at 60hz. It's kind of annoying. You can turn the 120v into DC though using a diode bridge, making them flicker free.
 
The power brick could be a neat idea. Would something like that be available at pretty much any electrical supply store?

Something I just thought of would be to use these. I thought it might be cool to wire up LEDs of different colors and be able to select what color you want the light to be via a 3 way selector switch.
 
Format _C: said:
RadioShack is way overpriced i got a 12Volt ac adapter for cheap http://www.bgmicro.com/prodinfo.asp...PWR1150&page=4&cri=PWR&stype=2&time_out=44:25 here don't forget to get a 2.1 mm socket for it to plug into also from bg micro. if you order there both things will be cheaper than that one item at RS
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I wasn't necessarily going to buy from RS. Hell, Walmart is cheaper than RS. Really though, I'd like to be able to go to a store and pick this stuff up, do it as a weekend project kind of a deal.

I'll look around BGMicro and see what they've got though. Maybe I'll hold off until next weekend.

Anyone have any ideas to make sure this can actually be used as a lamp to provide real usable light?
 
rm.o said:
Hooking up led's'to 120v is fine, have you ever seen the led chrismas lights? The only problem is they'll flicker at 60hz. It's kind of annoying. You can turn the 120v into DC though using a diode bridge, making them flicker free.
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You can see them flicker at 60hz ?

MD
 
MD_Willington said:
You can see them flicker at 60hz ?

MD
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i can too... just like a crt monitor set at 60hz drives me insane
 
If you're going to make it in that form factor, a CCFL is probably still the best option--LEDs put out light that is just too directional.

I can see LEDs flicker at 60Hz, too. Put in a full-wave rectifier and it should be undetectable. Add a nice big capacitor, and the LEDs won't even flicker at 120Hz.
 
The Brain said:
You can directly hook an LED upto 110VAC, provided you use the proper resistor to limit current. However, as you have identified this would be a little more dangerous then some other solutions.
Click to expand...
The snag with the resistor method is, you're wasting over 100V at say 15mA average (50% duty), over 1.5W. Twice that with a bridge rectifier. If you did need to do it that way (with appropriate safety measures) the coolest way is to use a capacitor's reactance to lose most of the spare volts as shown here.
 
Teancum said:
If you're going to make it in that form factor, a CCFL is probably still the best option--LEDs put out light that is just too directional.

I can see LEDs flicker at 60Hz, too. Put in a full-wave rectifier and it should be undetectable. Add a nice big capacitor, and the LEDs won't even flicker at 120Hz.
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The problem with a CCFL is that I'd still need to convert the AC power to 12VDC, putting me more or less back where I started, though the more I look at things, I think I might do this instead. I really hadn't thought about it, but it's a good idea.
 
The snag with the resistor method is, you're wasting over 100V at say 15mA average (50% duty), over 1.5W. Twice that with a bridge rectifier.
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That's why you put multiple LEDs in series, with one current-limiting resistor for the bunch--that means a lot less leftover voltage to drop, and a lot less resulting power loss. So with a full-bridge rectifier plus capacitor, you have 170V (non-RMS) /3V per LED = 56 LEDs in series plus a resistor to take care of the remainder.

I've thought this one through a few times--I'm planning on lighting a room with RGB LEDs running from household power sometime in the near future.
 
you people and resistors... wtf...

just go get a 10$, 5v-12v, 1amp DC wall adapter from walmart or order one off of the internet or something... and wire it up that way with smaller resistors... and this way it'll be converted to DC.

manually, you'd need a relay and a rectifier... not a really damn big resistor.
 
plot said:
you people and resistors... wtf...

just go get a 10$, 5v-12v, 1amp DC wall adapter from walmart or order one off of the internet or something... and wire it up that way with smaller resistors... and this way it'll be converted to DC.

manually, you'd need a relay and a rectifier... not a really damn big resistor.
Click to expand...

I was hoping to have a slightly more elegant solution than just the wall-wart. I might end up doing that anyhow, since I've pretty much decided to forgo LEDs and use CCFLs instead. It would be the easiest solution to my problems.
 
i see what you're saying, but for the given project... a small wall adapter verses a few chips soldered togethor is really the most elegant solution... and it's not like you need a fancy adapter or anyhting to do it.
 
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