led lamp question

[bigegg]

I'm toying with some ideas for lamps/light fittings for various projects - garden, shed, bedroom, camping, photography and just "art" to sell. the projects overlap to a large extent...

I'm looking at some "50w 220v full spectrum growing 380-840nm lights" at about $3 (£2.50) apiece.

is anyone familiar with them? how do they compare with (say) an (old style) 50w light bulb? there's no lumens/candlepower and seller is unresponsive.
I'm hoping they are like a floodlight?

what are they like when used for photography in terms of white balance?


how do they compare to a SAD lamp?

 

[Spot the welders dog]

Another seller followed from your link states:

Power: 20W, 30W, 50W (Optional)

Voltage: 220V / 100V (Optional)

Lumen Flux: 80-90lm / W

Beam Angle: 120 degree

Color Temperature: 380-840

Lifespan: Up to 50000H

Lamp Size (L x W): Approx. 60 x 40mm / 2.4 x 1.6inch

Package Weight: Approx. 10g

*Thanks for puting another project on my list*

 

[bigegg]

Lumen Flux: 80-90lm / W

so 4000-4500lm that will work

*Thanks for puting another project on my list*

 

[slim_boy_fat]

....shed, bedroom....

'Fess up.......

 

[WorkshopChris]

Am i correct in presuming these panels need quite a heat sink to keep them cool.

 

[bigegg]

'Fess up.......

tomato?

I'm rubbish at growing stuff.
notorious for it.
I told a friend at work so she bought me a plastic plant as a joke "kill *that* " she said.


I left it on my desk, above the heater vent.
it went brown.

 

[bigegg]

Am i correct in presuming these panels need quite a heat sink to keep them cool.

they are on quite a big piece of aluminium already.

 

[Barking Mat]

If you are not satisfied with the product or service ,please contact us and don't give us negative or natural feedback,We must give you a satisfactory solution.

cheap as chips, no natural feedback!

 

[Jetex]

They need to be screwed to a heatsink. I have some similar direct drive LEDs like these that are 20W each and they are in explosion proof lights.

 

[Jetex]

There are 5 20W LED's to make a 100W lamp, notice the big heatsink on the back. The front glass is about 10mm thick

 

[Pete.]

tomato?

Yeah, grow some 'tomatoes' you'll be popular with the local youth - and the local constabulary

 

[bigegg]

Yeah, grow some 'tomatoes' you'll be popular with the local youth - and the local constabulary

ooooohhhhhhhhhh.

 

[julianf]

Those units look cheap enough, but i would imagine mounting them on somthing that sinks the heat, whilst being aways from the live solder terminal to be slghtly awkward?

..you said "on quite large panels..." or something, but i dont understand?

 

[bigegg]

Those units look cheap enough, but i would imagine mounting them on somthing that sinks the heat, whilst being aways from the live solder terminal to be slghtly awkward?

..you said "on quite large panels..." or something, but i dont understand?

the led is on a 30x35mm piece of aluminium. exposed to free-flowing air, which "should" be enough?



this does raise a question that I've never had fully answered since i did A-level physics tho.

does electrical conductivity correlate with heat conductivity?
is it possible to have a material which conducts electricity effectively, yet which is an effective insulator to heat? (or vice-versa)

 

[bigegg]

or alternatively, the heatsink could be the live?

 

[julianf]

For something like that, disregard temperature. You're going to electrocute yourself on it no matter how warm it gets.

 

[julianf]

Or, to answer your question, if you want to carry the live with the heatsink, yes, it will work. The conductive area of the heatsink will be excessive compared to the current.

It will just mean there is even more to kill yourself with.

 

[julianf]

...which was actually my concern. If you mount these on an electrical conductor, the physicsl clearence between the 220v live terminal and the 220v AC is fairly small. One knock the wrong way and the whole heat sink goes live.

I mean I guess it does not really matter if it's all earthed correctly, but it just seems a bit borderline to me.

 

[voipio]

Looking at the advert, the term "full spectrum" is a complete misnomer. These LEDs have spectral peaks in the blue and red region, with no green, so the resulting light is magenta-coloured.

As for heatsinks, 85 lumens/watt represents around 12% efficiency, so of the 50W going into the LED, around 44W will be lost as heat. A 1degC/W heatsink will rise in temperature by 44 degrees, so become quite hot to the touch at an ambient temp of 20degC. 1 degC/W heatsinks are quite large. The ali plate on which the LEDs are mounted is nowhere large enough.

 

[bigegg]

Looking at the advert, the term "full spectrum" is a complete misnomer. These LEDs have spectral peaks in the blue and red region, with no green, so the resulting light is magenta-coloured.

As for heatsinks, 85 lumens/watt represents around 12% efficiency, so of the 50W going into the LED, around 44W will be lost as heat. A 1degC/W heatsink will rise in temperature by 44 degrees, so become quite hot to the touch at an ambient temp of 20degC. 1 degC/W heatsinks are quite large. The ali plate on which the LEDs are mounted is nowhere large enough.

thanks.
that's the sort of info I need.

it's beginning to sound a lotike "too good to be true"