OT: Just a thought.

Page 6 of 8  
It take a few more components than that. LEDs can't stand up to much PIV. Your lack of electronics knowledge is showing but to use your oversimplified analysis shows what a ballast could be composed of.
Calculate this 120 Vac across a 1K resistor. First of all your half-wave rectifier will net you about 180 Vdc if smoothed by a cap. That's a ballast loss of about 180 v squared / 1000 Ohms or 32.4 Watts of loss to run a half Watt LED in YOUR ballast circuit. IT would not be done this way but I had fun....LOL It would be done with high frequency inverter / P.S. and more complex circuits.
Just wait until tonight when GW gets out of school and will straighten you out. He knows everything! LOL
--------------- "Robatoy" wrote in message wrote: LEDs are current devices. Something has to absorb the excess voltage when you control the current supply to it.
Basic woodworking 101.
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It was oversimplified for a reason. But you seem to like the word 'ballast' so by all means use it (wrongly).
And you should make that correspondence course from a matchbook cover give you your money back.
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wrote:

It's not wrong.

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wrote:

Your capacitor (or resistor, switching current source, whatever) is the ballast. Something has to limit the current. Yes, it's called a "ballast". ;-)
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Nothing, absolutely nothing, in the set runs on 120V. An efficient switching regulator reduces your 120V, or 240V if you live elsewhere in the world, down to more useful voltages. Modern LED drivers also use switch mode technology to increase efficiency and reduce energy loss through heat to a minimum.
--
Stuart Winsor

Midland RISC OS show - Sat July 9th 2011
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The switching regulator is limiting the current. It's really an "electronic ballast".
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On Jul 20, 9:10pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

load=ballast. Check.
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wrote:

No, current_limiting_device == ballast. It does the same thing as an electronic ballast in a fluorescent fixture.
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On Jul 21, 12:19am, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Ballast = inductor (half a transformer... keeping it simple, remember?) NO LED circuit that I have ever seen used in backlit advertising signs has ever included a 'ballast' in the conventional sense. Choppers and resistors and diodes.... I know, all new technology to you... but it is not too late to learn. Now, if you want to burrow into a quagmire of semantics, knock yourself out.
By your logic, if a ship drags an anchor it is 'ballast' as opposed to what 'ballast' really is.
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wrote:

That is an example of a ballast, sure. That isn't the definition of a ballast, though.

You couldn't be more wrong. That series resistor *is* a ballast resistor. By "chopper", I assume you mean switching regulator. If it's used to ballast an LED, it's a ballast. ;-)
In case you hadn't forgotten, I'm a electronics design engineer, by day.

Nope. It's common usage.

Perhaps you're a sailor but I'm not claiming to be. I *am* an engineer, though. The widget in series with a lamp to limit current, whatever it may be, is called a "ballast". If it's a resistor, it's even called a "ballast resistor".
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On Jul 21, 6:29pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

I have a 1 watt LED and I would like you to give me the part number for a 'ballast' for it.
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wrote:

No problem. Give me the part number, the voltage would you like to operate from, and how much current you want through it and I'll give you the part number of a ballast for it.
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On Jul 21, 7:23pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

k> wrote:

So now you're talking a power supply?
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wrote:

I can give you a part number for that too, but you asked for the part number of a ballast for your hypothetical LED. I can't give you that if I don't know its operating conditions.
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On Jul 21, 9:29pm, " snipped-for-privacy@att.bizzzzzzzzzzzz"

o.uk> wrote:

Find me a ballast for LED lighting....sayyyy from these guys: http://ace-ballast.com/Pages/Home.html They have them for Fluorescents, and HID, but they use simple power supplies or drivers as they often call them to power LED's. So you're playing semantic ping-pong as per usual. Maybe that engineering degree is a bit long-in-the-tooth and an update is required. In commercial lighting, being it signs or for spaces, the power supplies for LED systems are never referred to as ballasts. Now if there is a resistor in that LED power supply that has a function (although not as an inductor) which acts similar to a ballast, one point for the semantics. End of discussion.
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wrote:

Semanitcs? Well, the current limiting resistor in an LED circuit *IS* called a ballast resistor. That's just a fact. That's what a ballast does (limits current).

Nope. I'm still a practicing engineer. Just designed a switching ballast network for an LED (laser diode, actually) today, in fact.

NOT THE POWER SUPPLY! A ballast limits current.

No end of discussion at all. It *IS* a ballast! A ballast doesn't have to be inductive. It can be resistive or capacitive, or switching (mimicking a resistor, capacitor, or inductor). The common principle is that it limits current.
It is semantics, I suppose, because that's what it's called. All words are "semantic".
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On Jul 22, 12:20am, " snipped-for-privacy@att.bizzzzzzzzzzzz"

Oh yes it is.
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He's right and you're wrong.
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So you say. Troll. http://groups.google.com/group/rec.bicycles.racing/msg/b0e49cbb25871e76?dmode=source george
--
fup2aukset


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