My first LED project (advice needed)

[LED09]

Hi all,

I'd like to make a grid of low power LEDs to light a shallow, small aquarium I've never touched a resistor or LED in my life so I'm not sure where to start (240v UK mains).

I'm planning on growing some aquatic stuff (plants etc) in rows of tanks and I want to run some tests to see how much LED light I need for each type. The light setup doesn't have to look aesthetically pleasing and just needs to be basic.

I'd like to start with 10 low power LEDs (evenly spaced out on a board) and add more each week to see the results. I could go up to 100 or more LEDs on each tank as I go.

I've been looking at low power LEDs on eBay and I've seen them in 3mm and 5mm. They don't mention the kelvin colour of the LEDs and I'm assuming Cool White is 6500k or over (which I need).

Seeing as I'll be adding more LEDs each week, would it be best to use a breadboard or is there a better way? Any advice is appreciated :thumbsup:

 

[evilc66]

I would ditch the idea of 3mm and 5mm LEDs right off the bat. Start looking at high power LEDs, as they will be far better suited to the application. You will need fewer of them (higher output, and wider angle), and fewer drivers/current regulators. Cool white 5mm LEDs can have a color temp of anywhere from 8,000K to 14,000K.

What I would do is use 1W cool white LEDs over each tank, driven by something like a Luxdrive Buckpuck. They are dimmable drivers, and you can use discrete resistors of certain values to set your drive current more accurately. The number of LEDs you will need per tank will depend on the size of the tank used.

 

[LED09]

Ok thanks.

The LEDs will be about 1" from what I'm growing with the water level in between.

I'm still trying to get my head around this stuff

For example, I've seen 10mm high power LEDs on eBay today (from Hong Kong) that claim to be 300,000 mcd. Thats 3x brighter compared to the 8mm LEDs that have around 110,00 mcd. The 10mm aren't mounted to a star for attaching to a heatsink like the CREEs. You get 50 for £17 with free shipping.

DC Forward Voltage: Typical: 3.4 V Max: 3.6V
DC Forward Current:100mA

Their 0.5w LEDs. IIRC, the wattage is V x I. Would that be 3.6V x 100mA? Wouldn't that be 0.36W instead of 0.5W?

 

[blasterman]

As per what evil said, we'd appreciate it if you'd ditch the idea of 3mm-10mm 'jewelry' LEDs and use 1-3watt power LEDs.

You get 50 for £17 with free shipping.

You get what you pay for. I have several LED PAR DJ lights that use *180* 10mm 25degree LEDs, and while the colors are pretty, they aren't that bright.

Unless you over-drive them or they are narrow angle, I have doubts if 50 of those cheap LEDs can even throw the lumens of a single 3-watt Cree. Plus, the Cree has published and verified specs including exact lumens, spectral out-put, etc. This makes it very easy to expand on your project if you decide to upscale in the future because you know what all the numbers are. Adding another Cree because you want to double the light is a lot easier than having to solder a couple more dozen 10mm LEDs.

 

[Gunner12]

For example, I've seen 10mm high power LEDs on eBay today (from Hong Kong) that claim to be 300,000 mcd. Thats 3x brighter compared to the 8mm LEDs that have around 110,00 mcd. The 10mm aren't mounted to a star for attaching to a heatsink like the CREEs. You get 50 for £17 with free shipping.

The MCD value is more of how much the LED will project. It's not a value of output. A 1 lumen laser throws a lot further then a 1000 lumen flood light because the laser concentrates all the light into a tiny spot.

For your application, you'll probably want a floodier light, which a bare high power LED will provide. You can get more then 4 Cree XR-Es from DX for the price of 50 of the 10mm LEDs. Each of those high power LEDs can probably match the total output of the 50 10mm LEDs.

They also have AC to DC converters on the site. Here's a 3w one. Anyone test then yet?

:welcome:

 

[bshanahan14rulz]

you should also look around on the internet for some aquatic plant forums. You may find that you need other colors in addition to white. Cool white has a good amount of blue in it already, and I heard plants usually like blue and red, in varying ratios depending on the plant. I dunno how important colors are, as the only plants I've tried to keep died (well, there was that dandilion that I neglected to pick, that grew alright...)

 

[evilc66]

Actually, cool whites work pretty well. Neutral whites are a little better, but the color temp isn't everyones favorite. A mix of both could work well.