You are correct to be concerned about over-driving an LED. They will then act as an expensive fuse, usually faster than you could react.
The power supplies meant for LED lights are should be specified as a current source…that is designed to produce a certain amount of current regardless of the voltage. The open circuit voltage, (where no current is possible), is usually limited to a safe range.
I have been using two LED lights for about 6 months now and haven’t had any problem. They are spotlights that I got at a clearance price from Home Depot. There are 3 advantages to them.
(1) They are incredibly energy efficient. One is 12 watts and the other is 10 watts. With these I can grow plants which would be impossible with similar sized florescent bulbs. I think they both produce around 800 lumens each within the spotlight area. (I will have to find the original box for more exact numbers).
(2) The other nice thing is how cool they run. I can lay them directly on the glass without any problem.
(3) They claim to last many times longer than the florescent lights. I usually need to replace the florescent lights after a year but don’t get around to it for another year.
The CREE light is the more efficient of the two lights I have due to a better designed power supply. The other light has a large heat-sink on the end that gets warm. I suspect that is where the power supply is.
I like the idea of the LED string mounted inside the ½ PVC pipe. I am now looking into doing that myself.
Bob

Thanks guys. So if I cut the strip into three equal lengths, then add a transformer to each shorter length, then I run the risk of over-driving the LEDs on the shorter length of light strip, correct?

So what if I cut the strip in thirds the way I described and then reconnected each length of lights to each other with an length of insulated wire soldered between each strip as a kind of drop leg from one level of my racks to another?

Comments?

Brian Perkins
www.wildperu.net

I don't see a problem with that. I assume you are talking about short lengths of wire about 10' or less.

Puting a connector in the wire may make it eysier to instal.

Hi, here's some data that may be useful:

Those LED strips are divided in sections of 3 LED chips plus other components (current limiting resistors) to operate at 12 Volts DC regardless of total number of sections (i.e. total length).

Each section is 10 centimeters long, uses a fixed current, about 60 miliamperes or so, and operates at 12VDC as mentioned above.

So you can cut the strips into sections and connect each section to a separate 12 VDC supply, as long as the power supply has enough current rating.

For example, suppose you have a 60 mA/section strip, and you cut a 2 meter (200 cm) piece. You have 20 sections at 60 mA = 1200 mA (1.2 Amps). You would need a 12 Volt DC power supply with a current rating of at least 1200 mA. It's OK if the current rating is greater.

You can also connect several sections to the same 12 VDC supply, again as long as the total current can be handled by the supply.

These strips are designed to operate in automotive environments, so they can handle voltages that fluctuate a lot, you don't need a regulated supply, as long as the voltage doesn't go too high, 14 or 15 is OK, 18 I would begin to worry, but they can probably handle 24 for a few minutes. That means you can use cheap wall warts, or battery chargers.

Great! Thanks for all the input. When the package arrives, I'll post photos of my struggles, er, I mean triumphs! Yeah that's the ticket!

Best,

Brian Perkins
www.wildperu.net

How did it work out?
I've bought several of these LED strips. Glued to a glass cover, with 12v transformers that I have lying around.

Wayne