TD Moose » Electronics

Side glow cable with LEDs

tdmoose — Fri, 06 Nov 2009 01:44:47 +0000

Many projects require illumination. An LED is often a good choice because it can be bright while using a minimum of current. An ultra bright LED can even drive enough light through short lengths of side glow fiber optic cable. This cable is flexible plastic cable with a reflective core to direct light to the side, as opposed to simply transmitting the light to the end of the cable. While it is designed to be used with bright halogen bulbs that push light through hundreds of feet of cable, I was interested to see how well an LED could work with just a few feet of cable.

My wife and I are interested in making safety clothing for night bicycle riding and thought this might be useful. We ordered a five foot section of 3mm wide cable from here. Once I had the cable in hand, I attached a bright red LED to each end with shrink tubing.

End connections

A quick test shows that two LEDs provides a fairly even glow along the entire length of the tube. Each LED was rated to deliver 18,000 millicandelas of light.

Two LEDs powered up

This looks like it could be used on a bicycle helmet to provide a flashing illumination. More to come as we experiment.

Improving a book light

tdmoose — Thu, 29 Oct 2009 02:43:04 +0000

I love to read. Often, I use a portable light that clips onto the book. It works OK, but two things bugged me about it. First, it required four AA batteries. Second, it used an incandescent bulb that is bright, but which produced glare and hot spots on the page.

Original bottom view

I had been experimenting with a simple circuit called a Joule Thief. This circuit boosts a DC voltage to a higher voltage. It’s is easy to make with easy to obtain parts. The Web is full of plans for these devices. The advantage for this project, is that such a circuit can drive a bright white LED from a single 1.5 Volt battery. I figured that I could easily fit the circuitry and a single AAA battery into the battery compartment of the book light. This would save batteries and provide a more even light across the page of a book.

Joule Thief

I replaced the incandescent bulb with a bright white LED that I encased in aquarium sealant inside of a short length of clear plastic tubing. This helped to diffuse the light along the approximately two inches of tubing that the LED was attached to. Here’s the final assembly and it’s use.

Ready to use

Modified lamp in use

Taking apart a Flip Ultra 30

tdmoose — Mon, 27 Jul 2009 15:53:16 +0000

The Flip camera is great and cheap enough to risk destroying it. Broken down to its bare bones, it is still a little bigger than its predecessor, the Pure Digital One-use camera. However, the built in USB port and connector, and the ability to connect the Flip to a PC without needing the hack it to access stored videos, makes it more useful in the long run. In short, a great camera for projects that need small, light, durable video recording hardware.