Help wiring an LED array

I'd like to buy some LEDs off ebay and build some LED arrays but I'm confused as to how to wire it.

For example, lets say I have 100 watts of LEDs (aka 1 watt x 100 LEDs or 10 watts x 10 LEDs) as an extreme example and each LED has a max voltage of 12 volts. Then lets say I have a power supply that provides 100 watts at 12 volts. How would I wire it? I'm worried that if I hook it up, lots of LEDs will just burn out.

Just help me understand what I need to watch out for here.

I'm obviously a super novice. Have pity.

1. The only proper way to use LED's is by having a current limiting resistor for each single LED.

Cheap lamps often have many LED's in series and only one resistor for the lot, if one LED fails the whole array is doomed.

For high power LED's cooling is also an issue, especially if stacked close to each other, a massive heat sink to mount them on is a must in most cases.

In case or Cree LED's or similar you will need a driver for each LED (if the LED is not already mounted on one). They can be used with home made circuits but usually I can not recommend such things for these types of LED.

2. The power supply depends on how you wire the LED's.

For example you can use a single LED on a 3V supply with a tiny resistor or 100 with bigger resistors on 12V.
Everything in between and above is also possible.

You have to keep in mind the power usage of the array!

For 100 LED's you simply find it not praktical to use a 5V supply as you would need something with insane high power levels, a short somewhere could mean fire.

Take your 100W example:

100W / 5V = 20Amps for the supply.

100W / 12V = 8.4Amps for the supply.

100W / 24V = 4.2Amps for the supply.

You always want the power supply to be at least 10-15% higher in the power rating than what you use it for to avoid stress and early failure due to overheating.

3. Make a simple testing station where you can test every LED once the resistor is connected - this way you avoid replacing dead LED's on the finnished array.

Do you have more info on the type of LED you have and what power supplies are at hand?

WillE2 (author)  Downunder35m2 years ago

As to specifics, I'm trying to augment some poor light in some of my windows for some plants I am growing. Especially in the winter, the poor plants don't get enough light.

So I've looked at a lot of stuff, and apparently what I need are some high powered LEDs. They're really only affordable if I wire it up myself. That is assuming I've figured what I'll need properly.

As to specifically what I'll use, I've bought nothing at this point.

I'm trying to figure out what I need to buy to make this work. The heat sinks don't look especially expensive. I think it is looking like less then 10 dollars per window. The LEDs for a given window look like they'll run me maybe 10 dollars or so. And then it is just power supplies and resistors. I've also seen people suggest that you use little voltage control chips instead of resistors because they're more efficient.

My goal is to try and make these lights for as little as possible and have them be strong enough to keep my plants healthy. They really need more light then they're getting and it seemed like a fun project.

LED plant lights often go for under 10 bucks on Fleabuy.
Between 3 and 10W for standard types, higher power levels of course cost a bit more.
If you prefer DIY and high power LED's I suggest to look for Cree LED's that are already on a heat sink, this way you can just screw them on an aluminim plate or similar.