LED replacement for 48" fluorescents

Oh, truth is an absolute defense here too, except if you can't afford to pay your lawyer. It isn't particularly rare for tap water to be a little bit discoloured when they've been working on the pipes, or if there's been a lot of runoff into the reservoirs recently. Round here we're blessed with excellent tap water, so that it doesn't need some big expensive filtering plant. Down in AZ I imagine they have to drill down to Godzilla's level and take what they can get.

Cheers

Phil Hobbs

Cheers

Phil Hobbs

If you think the dining room is bleak, have a look outside. San Tan Valley is in the Sonoran Desert. They do dirt and rocks really well there.

Cheers

Phil Hobbs

On a sunny day (Fri, 03 Jan 2014 08:28:56 -0500) it happened Phil Hobbs wrote in :

But also this:

google

It is not good practice to run ANYTHING at the maximum rating. Cree recommends 350 mA continuous. (I misstated the current, the commercial regulator is 350 mA.) The previous unit I built with my own regulator was 300 mA.

Jon

Yeah, we have one do that near the pool, huge, over 20ft. What a gooey mess.

But afterwards they wilt away. How did you preserve them?

OOPS, looked at the wrong line on the data sheet! Only 102 Lm/W. So, egg on my face!

Well, we'll have to wait another year or two for more efficient LEDs. I have pretty good heat sinking on mine, so I think they are running at a steady state Tj of less than 50 C. I have 2 square inches of copper per LED, in open air.

Still, the fact that I can replace TWO 32W 48" fluorescent tubes with one string of LEDs drawing ~ 22 W sounds real good to me.

Jon

No, 1 A absolute Max, "test" current is 350 mA.

I have an earlier 10 LED fixture running at 300 mA, and have been using it for ten months. Certainly no visible loss of output, yet.

Jon

You don't like desert ?:-) Everyone needs to understand that the Sonoran Desert is, unlike the Sahara, a "living desert" with significant vegetation. ...Jim Thompson

YES IT IS!! In the moonlight the desert glows. After moving here during December, at first I thought it had snowed outside the ground was so white. During the day, there's a purple sage that has an incredible 'shimmy' effect in the wind, too. And, a myriad of critters that run about. I still can't get over the amount of rainfall here! Seems to rain all the time. And, as a result, the trees and brush just keeps getting larger and larger! This ISN'T desert! Just a different flora.

Say, Jim, we should send Phil complementary Cholla cactus plants! In honor of ....?? Those things look soft and fluffy, at a distance!

Sun dried. They're amazingly durable. The aborigines use them to make thatched roofs. ...Jim Thompson

Yep. Just be sure he doesn't use gloves, or he'll damage the "fluffy"

...Jim Thompson

That's one fine looking dining room. Through the door, is that a butler's pantry or part of the kitchen?

We have the same rounded corner trim here, which I've had to go around and repair after running a ladder into an edge and finding over 7 other dented spots caused by work crews.

Learned how to 'invisibly' repair a dent in less than a minute now. Well a minute over several days.

Get a bucket of premixed joint compound. Keep your house paint sample. Use either distilled water or Walmart Glass Cleaner [cheap!] for thinning the paint. Get a very fine bristle brush [not necessary can use paper towels] to apply 'touch-up' paint. Get 220 fine sandpaper and a flat sanding block, perhaps 10 inches long. Do NOT use a soft sanding block!

Technique to fix a dent... Slather joint compound into the dent, overfilling the spot. Wait 24 hours and gently, flatly sand down. If done correctly the first time, you can paint. If you find you did not fill, just slather more in and wait another

You said you have grandchildren? You'll develop the skill if you have not already.

LOL! Several of those 'fluffies' went right through the sides of my work boots and almost up through the soles. They did penetrate the sides of my air-filled two wheel truck tires and the air went out pretty quickly. Still trying to think of a good application for something with those kinds of characteristics. As a result, our land has become a cholla-free zone.

Correction: I meant to say 120 lm/W at Tj=85 C, which is the temperature CREE uses in their characteristics.

I think we are quite close to the theoretical maximum. With 100 % efficiency a monochromatic source at 555 nm (greenish) would produce

Previously when doing thermal design, just multiply the actual voltage drop with current and noting the thermal resistances, you could calculate the temperatures at different points (junction, heatsink etc.).

Now that good LEDs actually emit a significant amount of the input DC power as visible light, the amount of DC power converted to heat will reduce and hence actual temperatures are lower than assuming all DC power is converted to heat.

Butler's pantry.

I'm almost out of "denting" grandchildren (current ages are 6, 13, 14,

Keep depilatory wax around ;-) ...Jim Thompson

I never sand joint compound. I smooth it with a damp sponge.

The coffin is in the bedroom. ;-)

Tim

A few years back I had a one-week-a-month gig in Albuquerque, where, coincidentally, they also do dirt and rocks well. I managed to maintain sanity by renting houses on VRBO instead of staying in hotels--it wound up being about the same price when I was done. I used to stay either in a casita in Corrales, or a bigger place up in Placitas, on the shoulder of Sandia Mountain, that had an amazing view, if you like dirt and rocks. I could see at least 30 miles across the Rio Grande valley.

One January in Placitas I made the mistake of leaving the window in my bedroom open a crack when it was about 5 degrees and 10% humidity outside. It got so dry inside that I woke up with various bits of my throat stuck together. I had to go stand in the shower for 10 minutes before my pipes were back to normal. So no, I'm not a big fan of deserts.

I've lived in Vancouver, Northern California, and New York, and visited lots of other places wet, dry, warm, and cold. Say what you like about the taxes and politics in New York, most of which will probably be true, still, I like the weather better than anywhere else I've been.

My opera singer daughter and I just finished an hour's work shovelling a foot of snow off the driveway and walk, in brilliant sunshine under a sky bluer than my jeans, singing Christmas hymns at the top of our lungs. Good medicine.

Cheers

Phil Hobbs