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Old 14th March 2014, 04:38 PM   #2311
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by rsavas View Post
AndrewT data is way off, better stick to audio, time to do a bit of research with examples from mfg data sheets and not come up with inaccurate data.
..............
Tha data led me to expect 90l to 100l per watt.
Some leds are now being developed that are getting around 160l per watt.

On that basis I took the printed data as a guide and bought LED replacements for Hologen bulbs.

I now have 9 different types from 7 different manufacturers.

I can assure you NONE get anywhere near the light output from a 10times higher wattage Halogen, No matter what claim the manufacturer makes.

I know that our eyes are scaled a bit like our ears in that they react to a log scale of brightness/power.
I estimate that in general LED replacement bulbs give about half the light of a 10times higher wattage Halogen bulb.

I stand by my original post
Quote:
the LED bulbs give about 5 to 7 times the light output for the same wattage as a Halogen bulb.
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Old 14th March 2014, 05:05 PM   #2312
rsavas is offline rsavas  Canada
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the LED cost trap!!
The bottom line is cost/economics,
A F54T5HO puts out ~4500 lumens for single piece cost of ~$5. Find any LED source that comes close to putting out the same light for $5?
As a working example,
Say a LED puts out 100 lumen, you need 45 of them!! so they have to be ~11cents each. Where do you find a 100 lumen LED for 11cents a piece? Now you have to mount all these LED's on pcb assemblies etc. Compare that cost to a simple lamp socket.
I can not see a LED ever competing on a cost bases as I described above.
Bonsai, you can control any light source remotely, it is not just for LEDs.
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Old 14th March 2014, 06:31 PM   #2313
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rsavas,
You can also have a screen in your refrigerator door today but it seems rather silly what some of the proposals are today. Do we really need to turn our lights on remotely from around the world? Though we can automate and control many things these days most of the application are unnecessary to say the least. I go hiking in the hills near my house and it is amazing how many people can not put down their phones, they are connected 24/7 and don't even see anything around themselves. We have become to immersed in this technology to enjoy what is already there.
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Old 14th March 2014, 07:16 PM   #2314
RNMarsh is offline RNMarsh  United States
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Like everything else, convenience and longer life cost more. Like with batteries... longer life ones will cost you more. These alternative bulbs are mostly about longer life and the convenience they give in not replacing them as frequently. Especially if the lights are high up in a ceiling etc. With some types, I can install them and pretty much forget about them for 10 years. AND, I can get 'white' light (6500 degree light... close enough) which i cannot get with incandescent bulbs. Are they over-priced? yes, of course... for awhile.

-RNM

Last edited by RNMarsh; 14th March 2014 at 07:27 PM.
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Old 14th March 2014, 08:32 PM   #2315
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Quote:
Originally Posted by Kindhornman View Post
rsavas,
You can also have a screen in your refrigerator door today but it seems rather silly what some of the proposals are today. Do we really need to turn our lights on remotely from around the world? Though we can automate and control many things these days most of the application are unnecessary to say the least. I go hiking in the hills near my house and it is amazing how many people can not put down their phones, they are connected 24/7 and don't even see anything around themselves. We have become to immersed in this technology to enjoy what is already there.
Ah , you speak of the "little black box people ". They don't know where they
are without GPS. No knowledge of geography,direction, (moss on the N
side of trees). So reliant on that tech they would be frantic and
stressed without it.

I actually have to memorize the city/area ... I still know exactly
where I am by landmarks (mountains/ buildings/rivers). Remember
addresses , phone #'s ,commitments with just little notes or memory.

We are forced to have a "dump" of info in this tech age. The home PC
is a good repository for the mass of useless required info that we
must have at our disposal.
I have no (dumb)phone ... !! But at least I won't be getting Alzheimer's with
lack of use.

OS
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Last edited by ostripper; 14th March 2014 at 08:35 PM.
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Old 14th March 2014, 09:24 PM   #2316
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OS,
I have resisted the smart phone upgrade, my kids have them and I don't need to be connected to the internet every minute of the day. You are so right it seems people do not know how to read a map these days, need a gps nanny to tell them which way to go and where North is. Asking someone for directions to somewhere today is a joke, they want to pull up map quest and then they don't know what they are looking at anyway. I guess the old Boy Scout in me has learned a few things that still come in handy.We had Heathkit and could solder and build something and today they have Arduino and just plug things in. And tell someone to machine something on a non CNC machine these days and they wouldn't know what to do. I guess this old mind is still working pretty good for being from another Century!
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Old 15th March 2014, 02:31 AM   #2317
Bonsai is offline Bonsai  Taiwan
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The real useful application for smart lighting is in commercial applications - buildings, warehouses, shopping malls etc where the control aspect can bring significant cost savings.

I know whereof I speak . . .
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Old 15th March 2014, 04:26 AM   #2318
mt490 is offline mt490  Australia
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Quote:
Originally Posted by AndrewT View Post
Tha data led me to expect 90l to 100l per watt.
Some leds are now being developed that are getting around 160l per watt.
And as the reviews show, barely any commercially available lamps reach any of those numbers at this time: LEDBenchmark - Unbias LED lighting reviews.

Most LED downlights, especially drop in ones, suffer from only having sufficient light at the hot spot. The drop in body sizes of MR16 and GU10 are only good for dissipation up to around 6W given the practical constraints of LED emitter temperature. Consequently most 'drop in' bulbs at present miss the mark on replacing a 50W halogen altogether. You need about 10-12 Watts of LED power at least.

Really for the price and results nothing beats fluorescent tube lighting for workshop illumination. It gives you the minimised shadow flood effect, retains fairly good colour and energy performance (as long as you don't go for bottom shelf parking lot grade tubes), solid life expectancy and is quite cheap to replace versus any equivalent in LED.

The advantages in practice going for LED for this are not really that major at this time.

Last edited by mt490; 15th March 2014 at 04:30 AM.
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Old 15th March 2014, 05:02 AM   #2319
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I'll stick to using led's as audio amp
current sources (or cascode references ) , use at low If ...just for their Vf.
Makes for purdy' amps , too.

HO fluorescent's are the ticket.

OS
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Old 25th September 2014, 09:52 PM   #2320
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Quote:
Originally Posted by Edmond Stuart View Post
Cherry stated that these caps are crucial for stable performance. So if it is not (a mild) shunt compensation, what else it could be?

Cheers,
E.
It is a negative feedback capacitive path, generally to compensate for the input pole of the gain device being compensated.

It's the same kind of capacitance you put at at opamp's output to negative input, to increase stability, by bypassing anything that's in the global loop at a certain frequency (that darn outputstage that's a lot slower than the driving stage)

When you look at a transistor as a gain device, you can look at one this way:
-Base/Gate: Input(+)
-Emitter/Source: Output(+)
-Collector/Drain: Output(-)

A transistor or FET is the smallest unit of (inverting) gain device; a stage comprising a number of transistors most often also yields an inverting stage to which this feedback can applied. Think VAS input, output stage output.

The usual miller cap is also just that, a capacitive negative feedback path from the (Multi)transistor's output to input for stabilizing purposes.

Hence, I've termed capacitors that compensate gain devices by connecting the output inverted to the input (either by an inverting input OR output) "local feedback" capacitors. Because it's feedback around a single device.

Now, when you tink gain devices made up of several transistors, you can keep thinking the same way: Local to that device. That's what "cherry" compensation is: a capacitive negative feedback path that includes the output into the VAS. The output, with respect to the VAS input is inverting.

These caps one finds all over the place in nested loop systems to keep inner loops sane and stable. To coin differently each and every feedback cap configuration, while all they are is mere negative feedback caps to the gain unit (one or more transistors /stage / stages) for stabilization purposes, is a bit uhm... ridiculous? Also given this view (a simple capacitive negative feedback) it can't be called anything special on its own?

TPC describes just one feedback path, the rest attempts to describe various combinations of local and extra-local (next nesting level, not always the global loop) compensation.

So with respect to the "Cherry" compensation and mandatory "shunt" compensation; if by "Cherry" you mean you take out the basic miller compensation and "include" the output stage instead, you've effectively taken away stability from the inner, local loop. That's why those "shunts" are needed, It looks odd, a cap from supply rails to the base/gate, but in effect, they are local NFB loops to the gain device.
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