EEVblog #50 - Solid State Cree LED Lighting, and How Thermal Design Sucks.

Dave lights up his new backyard deck with Cree XPG LEDs, and then winds up measuring the wind from a storm instead. And do you know the difference between efficiency and efficacy?

Category:

Science & Technology

Tags:

• sold
• state
• cree
• xpg
• star
• led
• luxeon
• light
• lights
• lighting
• home
• heatsink
• thermal
• design
• efficacy
• efficiency
• calculations
• lumens

[jasonuscg]

Somehow I watched the whole video... Talk about waste and efficiency this 21 minute video could have been done in 7, not very efficient.

He sounds like Herbert form Family Guy!!!

[EEVblog]

@jasonuscg It's called a conversational off-the-cuff style. If you think it's too long then you go redo it in 7 minutes. I'll give you a week, but remember - no script and no retakes - I'll trust you. Once you are done, post it as a video reply so we can all critique your style.

[OldSkull87]

What are ussually good working temeratures for LEDs? Or at least safe? I've built for myself small lamp, geat for working - it's small, portable, with LiIon accu - and rather bright (2 3W 120lumen LEDs - weak and cheap ;) ), but on full power (it's regulated with pot.) it's 6W cooling on maybe 50cm2. When on 50% it'c slightly warm. But on 100% it's 90*C measured on STAR just at the diode - which means ~110*C. I'm using it ~4h/day - how long will it work? Should I lower maximum power?

[EEVblog]

@OldSkull87 Impossible to say unless you have the reliability specs for the LED in question and you can accurately measure the junction temperature. The generic answer is "as low as possible"

[oehrlein49]

Nice video! What are you using to drive the LEDs? do you have a current source? or are you just applying a constant voltage and using a current limiting resistor in series?

[EEVblog]

700mA constant current. See my website for the links.

[EEVblog]

Did you check the heatsink compound undernearth? If that's not in good nick then you might indeed have a problem.

[PawnozTV]

you remind me of the joker before he was evil/crazy

[wjr123able]

I don't know if someone has already noted this but the maximum possible efficacy of a light source is 683 lm/ W, for the case of monochromatic 555-nm green light. The maximum possible efficacy for an ideal white light source is 240 lm/W because the human eye is less sensitive to wave- lengths on each side of green.

[junk250]

You are wacky lol, but good info in the vid.

I don't have electronics background, but you can get decent led technology cheap these days. Definitely the future of lighting.

I have a couple of led flashlights, with xm-l cree.

They are awesome !

[dasraiser]

awesome shirt :D see you 100 years ago

[LightingShowroom]

Interesting

[shoney]

arctic silver does make pastes.

[frosty1433]

why do I always find myself making fun of the way this guy talks?

[AxelTiger]

@jasonuscg

well if you think you can produce a more 'efficient' video then off you go! link it to me when your done! I'll be waiting..

[TheBlueCoyote]

my said she doesn't understand most of what he's talking about but likes his accent!