The Lampshade LEDening: LED project #1
Sometimes I think LED strips are the greatest thing since sliced bread. I mean, why install a simple 120V light socket when you can muck around with 5m-long strips and power supplies? Well, whatever, I think they’re fun and useful.
I’ve already installed 5m strips in my basement, storage area, and under the kitchen cabinets, but now my thoughts are roaming to more creative, less utilitarian uses. So allow me to present my project #1: a new bedroom lamp.
The finished lamp
The unusual shade was a gift some years ago. Till now, it’s just decorated stair landings, lit up with a tealight candle once every π blue moons. But with my dark new bedroom needing more light, I started to ponder how I might combine the shade with LEDs.
It didn’t take much thought to come up with a LED strip spiral concept, but the details remained vague.
My chosen LED strip was relatively high-powered, dissipating about 25W over its 2.2m length, and thus heated up more than average. My temperature concerns led me to the solution: wrap the strip around some sort of heat-sinking cylinder. The only metal tubing I had lying around was standard copper water pipe…too small a diameter. But…I did have a roll of aluminum foil. Eureka!
LED strip & heat sink
I did a dry fit of the strip spiraled around the foil roll. It looked good. So I peeled off the adhesive backing and assembled the pieces.
The finished LED assembly
Even with the heat sink, the whole assembly still got fairly toasty. But that was with the foil roll standing on the floor. Lifting it a bit off the floor got a chimney effect going up inside the roll, which dropped the temperature to something more reasonable.
Using fishing line to suspend the roll. It's also secured by line at the bottom.
All the parts. I’m waiting on a footswitch, which will be installed on the AC cord.
As I've investigated in previous blogs, long LED strips tend to drop voltage the farther you get from the 12V connection point. To minimize this, I soldered the 12V connection to the centre of the spiral.
The 12V PSU is another Chinese special, rated at 5A – over twice the lamp current. It does work up to – and a bit beyond – its rated current, but it gets pretty warm, and the DC wire drops a volt. Practically, I wouldn’t use it for much over 3A.
—Michael Dunn is Editor in Chief at EDN with several decades of electronic design experience in various areas.