Andrew Morris designed a dimmable LED driver circuit that is simple and energy efficient. He then installed the circuit into a portable fluorescent lamp.
My new LED desk lamp is just what I need. I set it on a table beside my easy-chair. It produces a natural white light, like daylight. The light from the LED array is very focused, like a big flashlight. BTW, you should use LEDs with a viewing angle of 30 degrees or wider. The dimmer greatly enhances the lamp's utility. I can turn the brightness up for easy reading, or I can dim it down to the point where it perfectly illuminates my laptop keyboard, without the hassles of my USB light. Turned all the way down, the lamp produces enough light to illuminate my TV remote while not affecting the view of my TV. I also use it as a nightlight. I also use the lamp as a work light, because it can be folded or rotated to illuminate my work surface, without being in my way. The lamp is very portable and is much lighter than it was, having lost its heavy ballast coil and glass tube.
The original 9-watt fluorescent tube in the lamp costs about $5 and lasts about a year with heavy use. I spent $21 on the LEDs I installed in the lamp and they should last for many years of heavy use. The remaining parts cost about $10, not including the lamp itself. The 72 LEDs produce plenty of light for reading. The lamp does not light up the whole room like the fluorescent version did, but it brilliantly illuminates whatever it's aimed at. At its focal-point it's a lot brighter than the 14-watt fluorescent lamp (with a new tube in it) that I had been using for reading. The color is better, too. Now, I'll just use my fluorescent lamps for area lighting.
You could use my circuit to create your own custom LED lamp. You could make a beautiful LED desk lamp out of wood. My father was a skilled furniture maker, who went into electronics when his employer moved to an assembly-line manufacturing style. When he got engaged to my mother, he had no money for a diamond engagement ring, so he made her a small, but very beautiful wooden table lamp. That lamp was far more precious to her than any diamond ring could have been. One of my sisters has the lamp now.
Good job in creating what you need. It looks like it will last for many years. I have built standard incadescen lamps for family gifts, but next year, I might switch to LED. Great article.
Thanks for the kind words. I'm a retired electrical engineer, living alone with nothing else to do. I don't sit around looking for stuff to create. It just happens. I see a want or need and create a solution. This blog needs more gadget submissions from other people. My ugly face is showing up a bit too often. :-)
Nice application, Andrew. Looks like the only significant cost here was the isolation transformer, at $21. By the way, if you or any reader has a good LED holiday light application, please send me a photo. As we did last year, we'll be running good photos of LED light strings at the holidays. Send to charles.murray@ubm.com.
The isolation transformer is not actually part of the project. It is a safety device for people who breadboard and test line-powered circuits that are not isolated from the power line. You should have an isolation transformer already if you do this kind of work. The components that are part of the lamp itself are quite cheap. If you just build the circuit and don't breadboard it or test it with anything but a voltmeter, you won't need an isolation transformer.
Because the LEDs are very directional, the lamp can illuminate your reading material very brightly if desired, without lighting up the room, disturbing your spouse's sleep.
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