Best LED for yard floodlight

[KrisP]

Hi,

I'm looking to make a 6 LED floodlight for my backyard which is about 15m x 20m. I'm unsure which LED's to use but they will be mounted on a large heatsink. I've made a 3 x Seoul U-Bin W0 light without reflectors as a lamp for indoors and like the flood it provides but it's not enough light to light the yard adequately. I've also made a 4 x Seoul U-Bin W0 Maglite which had IMS 20mm reflectors which did a great job of lighting up the center of the yard and had a fair amount of spill. This would be perfect with 6 LED's BUT it will be on during all hours of darkness and I don't think Seoul's running at 1A for 12 hours at a time will last too long. I've heard of them changing tint to blue at this power over long periods, i'm not sure if this is appropriate to my situation.

I have no experience with Cree's except my P4 L2D-CE flashlight and a Q2 aspheric Mag, so I can't really see how much flood a Cree would have without a reflector but I know that they'd run at 1A perfectly fine.

Basically, i'm looking at Cree P4's with or without reflectors or Seoul U-bin W0 or V0 with or without reflectors. Tonight I will be checking which Seoul tint I prefer for outside lighting. I much prefer the V0 for inside lighting.

Please help!


Thanks in advance

 

[KrisP]

I just tested my 350mA 3 x Seoul U-bin W0, 400mA 3 x Seoul U-bin V0 and 1A 3 x Seoul U-bin W0 outside. The difference in colour tint is quite difficult to actually see in a garden area with no white areas, so the tint doesn't really matter. But i've realised that 6 LEDs is going to be overkill unless I plan keep all the neighbours awake by my glowing yard.

I think 3 x Seoul's, one with a reflector and two without reflectors running at 1A or so will be more than enough light.

I'm not 100% on this though, so if you think the Cree's would suit my application better, please let me know

[edit] I just took the head off my Q2 aspheric mag and put my L2D-CE next to it, the Q2 with no reflector has enough flood/spill and the P4 in the reflector gives a good spot in the middle of the yard. I already had a spare Q2 so I just ordered 2 more and a '172 6x25 Degree Collimator for Cree XR-E' for the center LED.

I have enough Seoul lights, so I decided to make a Cree fixed light for once

 

[moon lander]

i always prefer crees for reflectorless flood because they have a narrower beam than seouls. that means brighter in front and just a little less to the sides. also less annoying to look at from the side. sounds like a really cool project.

 

[AndyTiedye]

The Mule is a reflectorless CREE.

Don intends to make Mule heads available eventually for fixed lighting (see post 87)

 

[KrisP]

Thanks for the replies

I'd read through that thread a while back and totally forgot about those heads he used.

Slight change of topic... Since i've been making 3 LED lights with 12v supplies, i've been using current limiting resistors as they're not really wasting much power, only around 1W or so. I was just wondering what would happen is I used a current regulator on the 12v supply, so still 12V but limited to 750mA output, what would happen to the LEDs? Would they toast because of the 4v each supply or would the current limit keep them alive?

Thanks

 

[AndyTiedye]

Thanks for the replies

I'd read through that thread a while back and totally forgot about those heads he used.

Slight change of topic... Since i've been making 3 LED lights with 12v supplies, i've been using current limiting resistors as they're not really wasting much power, only around 1W or so. I was just wondering what would happen is I used a current regulator on the 12v supply, so still 12V but limited to 750mA output, what would happen to the LEDs? Would they toast because of the 4v each supply or would the current limit keep them alive?

Thanks

If you limit the current to 750 ma, the LEDs should be fine.

 

[1 what]

If you're happy to be brave enough to forget Crees and tate a step back in time have a look at the Lamina BL-3000 series light engines. They have nice optional optics plus a very sexy (and adequate for long term use) heat sink. I think I purchased mine from Mouser Electronics who are very reliable and will ship world wide.

 

[X_Marine]

Sounds like a very interesting project. When can we expect some pictures.. :thumbsup:

I have been wanting to do something similar because I keep a small automotive type battery on trickle charge and it supplies my alarm system and motion detectors so I have always wanted to add some smart lighting especially for power outages.

Let us know what you come up with.

ThanX
X..

 

[KrisP]

Well I found a suitable host, see links below. I have stripped the internals out and have several heatsinks I can secure in there to mount the LED's onto.

I made up a light sensor circuit so that it will only turn on at night, but i'm not sure if I should mount that in the light or separately. I will probably put it into it's own housing and mount it externally.

The light is just going to have a DC power socket and the separate power supply (just a 24VAC to 12VDC / 2A plug pack) will have a 3-way switch for OFF/350mA/1A which will just be done via resistors.

Now I just have to wait for the LED's to arrive

 

[KrisP]

I've just come across a strange problem... I've been using 240vAC -> 12vDC power packs to run lots of 3 LED's with no hassle thinking 12v @ 700mA is only 8.4W plus maybe 10% losses in the power pack so about 9.5W total.

Today I made up a lead I put before the power packs to measure the AC current drawn. I measured two lights; a 12vDC @ 1A and a 12vDC @ 350mA and was surprised to find that the 12vDC/1A light was drawing 55mA @ 240vAC (13.2W) and the 12vDC/350mA light was drawing 65mA @ 240vAC (15.6W)... Very weird.

Then I measured the power packs with no load... The first pack that was running the 1A light was drawing 8.6mA(2W) with no load and the second pack that was running the 350mA light was drawing 40mA(9.6W) with no load.

I tested a few others and they all measured above 20mA(4.8W) with no load.

Power packs seem to waste a fair amount of energy just by being plugged in... It totally defeats my purpose of replacing my flourescent energy saver globes with LEDs! :mecry:

 

[LED-FX]

Transfomer wall wart will lawys use a bit of power by being plugged in regradless of load on secondary, switch modes can be a bit cleverer but power factor means less easy to accurately monitor.

Cheers
Adam

 

[brickbat]

I tested a few others and they all measured above 20mA(4.8W) with no load.

There's your mistake. With AC circuits the power is Volts x Amps x PF. What's PF you ask? Power Factor, and it relates to the phase shift between the current and voltage. It's value will be less than 1 for loads like power adapters, so the 4.8W you calculate is the worst case, and if you can get a real wattmeter, you'll probably find you're using less than 1/2 of the 4.8W.

 

[KrisP]

Thanks for the explaination