On 11/28/2014 9:34 PM, Jerry Stuckle wrote:
On 11/28/2014 7:05 PM, rickman wrote:
On 11/28/2014 6:16 PM, Jerry Stuckle wrote:
On 11/28/2014 5:24 PM, wrote:
In rec.radio.amateur.boatanchors Jerry Stuckle
wrote:
On 11/28/2014 4:11 PM, wrote:
In rec.radio.amateur.boatanchors Michael Black wrote:
On Fri, 28 Nov 2014, wrote:
In rec.radio.amateur.boatanchors gareth
wrote:
These LED replacements for 240V mains lamps; if one were to
open them, would one find a high voltage regulator suitable for
some of our valve experiments and repairs?
As the regulators are potted in and would be difficult to remove,
and
since LED's run on voltages on the order of 2-3 volts, no.
How many 3 volt valves can you name?
I think that point was that if a regulator was used to drop the line
voltage to those 3volts, it could handle high voltage input. The
probably
false assumption is that the regulator would be variable from some
very
high output voltage to some very low output voltage, so one could
use it
for tubes by making that adjustment.
Given that manufacturers want the least cost in a product, and the
regulator in a light bulb would have no need for a variable regulator,
and that these things are made in the millions, it would be extremely
silly to assume that the regulator is anything other than a fixed
regulator for LED's and is designed to handle the load of some fixed
number of LED's.
Once again, incorrect. Have you ever heard of "dimmable LED bulbs"?
How do you dim without an adjustable regulator?
You do realize that a dimmable light bulb is dimmed by changeing the
supply voltage and not by anything else connected to the bulb?
For incandescent, yes. But not for LED bulbs. If that were the case,
why would some LED bulbs be dimmable and others not?
To specifically answer your question, you design a regulator who's
output
is some precentage of the raw input as opposed to a regulator who's
output is always equal to some reference voltage.
Again, it all depends.
And to be yet more specific, since LED brightness is proportional to
current and resistors would waste power, the regulator would be a
current regulator with an average current output proportional to the
raw input voltage.
Then why can't you use standard incandescent dimmers with LED bulbs?
A lot of IC regulators can't handle high voltage. If nothing
else, nobody
saw the need, it was the solid state age. So dissipation issues
aside,
most regulators expect at most a relatively low DC voltage input.
True for IC regulators. Hoever high voltage transistors exist these
days which makes designing a high voltage regulator pretty trivial.
Sure. But how do you handle the current requirements without some kind
of transformer?
Well, assuming you want some voltage greater than the wall plug maximum,
the need for a transformer is pretty much a given unless some sort of
voltage multiplying rectifier is sufficient for the need, which is
where the current requirement becomes relevant.
However, the subject was high voltage regulators, not where does the
raw high voltage come from.
And where do you get the current necessary to supply the LEDs in the
bulbs? A typical LED required around 3V (usually 2.7V to 3.3V,
depending on the LED)? A 9 watt LED would require 3 amps of current.
Or, if the LEDs were in series, something less. But without a
transformer, the current would still exceed that of an incandescent bulb.
You obviously are unfamiliar with the structure of LED bulbs.
You two are both speculating and have limited information to base either
of your opinions on. Jim says,
You do realize that a dimmable light bulb is dimmed by changeing the
supply voltage and not by anything else connected to the bulb?
which is not correct in that most dimmers work by reducing the phase
angle of the applied AC or to reduce noise some simply don't turn on for
entire half cycles.
Jerry says,
Then why can't you use standard incandescent dimmers with LED bulbs?
Which is wrong because you can use "standard" dimmers, but the LED bulb
has to be designed for it.
Try reading a little...
http://www.ledsmagazine.com/articles...-magazine.html
Rickman, here's a better page from the manufacturer of dimmers (and one
of the lines we carry):
http://www.lutron.com/en-US/Educatio...LsandLEDs.aspx
Note the paragraph under "Do all LED and CFL light bulbs work with all
dimmers?"
That has even less information than the page I referred you to.
Your link says nothing about LED lights in general, only the Lutron
devices. As the article I referenced indicated, LEDs can be made to
work with generic phase control dimmers and the several LED bulbs I have
that work prove the point. I especially like Lutron's compatibility
list. They have a wide definition of "compatible"....
"Products on this list are considered compatible with the respective
Lutron C·L dimmers. Depending on the quality of the bulb you select,
compatible bulbs may still:
- have less dimming range than an incandescent or halogen bulb
- dim less smoothly than an incandescent or halogen bulb
- flicker or shimmer at certain light levels
- buzz"
LOL. If the combination does any of these things I don't consider that
to be "compatible".
Actually I find Lutron to have some real crap product as well as very
poor customer support. In order to assure I could get compatible dimmer
and lamp, I bought an LED fixture that listed part numbers for
compatible dimmers (tested in conjunction with the dimmer companies) and
bought a compatible Lutron dimmer. The result was they didn't work
properly. Clearly this particular fixture was *not* compatible with
generic dimmers and wasn't even compatible with the specified dimmer.
I contacted both Lutron and the company who made the fixture. I don't
recall the response of the LED fixture company but Lutron simply
recommended another dimmer with no mention of why they were on the
compatibility list and yet were not compatible.
--
Rick