I bought an LED light strip - and have questions...

[keltex78]

I'm assuming others here have bought and installed these LED light strips around their home...

I recently purchased an LED light strip from FastTech, to use as an under-cabinet light in the kitchen.

I purchased this strand from FastTech:

5m, Warm-White 300-count 5050 emitters, 72W/Roll:

https://www.fasttech.com/p/1268303

Based on the specification of 72Watts/roll @ 12v = 6A, I purchased this 10A 12V PSU to use with the LED strip:

https://www.fasttech.com/p/1270307

Now, when I connect the strip to the power supply, it lights up, but my multimeter is only showing ~1.4A through the circuit. Also, when I check the output voltage under load, the voltage is dropping to ~10.3V! There is a voltage adjustment screw on the power supply that will raise the output voltage while unloaded, but the 10.3 voltage reading under load is at maximum.

These values give me a total wattage of ~14.5W, about 5 times less than spec.

Further reading shows that a 5050SMD is rated at 192mW: at full power, the LEDs alone should be consuming a max of ~57W.

• Am I missing something here?
• Are the specifications for the strip incorrect?
• Is my power-supply under-performing?
• Is the resistance of the traces on the 5m/16ft strand of lights resulting in a severe voltage drop?
• Should I connect the power supply to BOTH ends of the LED light strip, or even break the strip (As it will be cut for installation) and connect power to both ends of each section?

Ultimately, my plan is to mount the LED strips onto leightweight aluminum strips. The aluminum strips would be cut to length, and then mounted via screws to the underside of the cabinets to illuminate the countertops. The aluminum should be a cleaner surface for the LED strips to mount on, while providing a degree of heat sinking for the LEDs.

Overall, I really like the light produced by these strips, I've held them in place under the counter and they produce a good amount of light. I may purchase a second strip to install as well, and then wire them separately so you can power a single strand for accent lighting or both for an ultra-bright workspace light.

If anyone has any thoughts or experience using these light strips, feel free to chime in!

[texaspyro]

The Tao of Chinese LED Strip Lights

I recently converted all 300+ lighs in my house to LEDs (see My adventures in LED home lighting). In my master bedroom are two bookcases with under-shelf light strips made up of small incandescent bulbs. They work, but have a nasty trait of causing the shelves to pop and creak for over an hour as they heat up the wood. Plus they are incandescent... that just won't do for the techno-villa. If you've ever trolled Ebay, etc for LED stuff you have seen those LED strip lights. These are stri…

[keltex78]

Thanks for the link TexasPyro! I really REALLY wish I had seen that before I had ordered the waterproof strand. Being for kitchen use, I felt the waterproofing would have helped with the cleaning. I didn't think it would kill the emitters...

I think I may go ahead and order a non-waterproof roll for this installation since it will be used a lot and save the roll I have for another project I have where it won't see the same heavy use. ...Or order two rolls and double up for a much brighter light...

When I get home this evening, I'll try wiring end-to-end like you recommend and see if that improves performance.