# Do LED's need a ballast?



## 480sparky

Not that I know. They may need a resisitor, though.


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## TOOL_5150

most LED's need 1.5 volts DC. So: they need a rectifier, and a resistor.

~Matt


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## Elec-Tech

Alot of them need led drivers(ballasts)


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## TOOL_5150

Elec-Tech said:


> Alot of them need led drivers(ballasts)


Well, what are we specifically talking about? A LED lamp, or a single LED? He said LED, so all it needs is correct Direct Current.

~Matt


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## Elec-Tech

TOOL_5150 said:


> Well, what are we specifically talking about? A LED lamp, or a single LED? He said LED, so all it needs is correct Direct Current.
> 
> ~Matt



This is true...need a little more info.


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## 480sparky

TOOL_5150 said:


> Well, what are we specifically talking about? A LED lamp, or a single LED? He said LED, so all it needs is correct Direct Current.
> 
> ~Matt


I see nothing about an LED lamp or bulb in the OP.










I just see a question about LEDs.


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## Toronto Sparky

I seem to recall an LED that was red with forward polarity and green with reverse polarity when you supplied it with ac it was yellow.

Or was that neon? 

The mind is the first thing to go


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## kbsparky

An LED by definition is a _diode_ so it doesn't need a _rectifier_ to operate.

That being said, connecting a pure LED to an AC source will cause it to "flicker" as it will only be lit half of the time.

If you use a rectifier in a power supply for an LED, that is simply part of providing a DC source to make the LED stay lit 100% of the time.

LED "drivers" as they are called are simply regulated power supplies, which may contain one or more of the following: Transformers, rectifiers, resistors, capacitors, etc. Calling that a "ballast" would be a loose translation, IMO.


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## gold

I beleive the driver circuit would look something like this (full wave bridge rectifier) with the possable addition of a small dielectric filter 
http://www.faqs.org/docs/electric/Semi/03263.png


added 
*BALLAST CIRCUITS FOR DISCHARGE LAMPS*
http://www.freepatentsonline.com/3787751.pdf

certainly very similar, the only difference i see is the ballast contains a capacitor (probably as a filter) If the driver contains one as well then its pretty much identical.

those probably aren't the best examples considering one is 3 phase but you should get the idea


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## CDTVegas

Hey All,

Good thread thus far. I'll be more specific.

Commercial office building:
- CREE LR6: http://www.creeledlighting.com/lr6.htm
- PAR30
- MR16

I understand that commercial buildings are typically wired for 277 V and Residential wired for 120 V. 

So there is a CREE 240v. If office building is 277v, then would you need a ballast?
*
*​


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## kbsparky

That type of adapter would not be subject to 277V. A PAR30 bulb fixture would be connected to a 120 Volt source.


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