This project was born out of the demise of a standard halogen torch lamp. With the fixture no longer working, I decided this would be a prime opportunity to recycle the lamp and go a little greener in the process. The original lamp used a 300 watt halogen bulb; my plan was to replace the bulb and fixture with an (60) LED array that would use approximately 14.4 watts at full power courtesy of a standard 12V power supply.
DOA halogen donor lamp
For the bulbs, I decided to go with 20mA, flat top, 5mm, wide angle, 22k white LEDs sourced from eBay. I used a standard acrylic plate as a mounting bed and laid out the bulbs in 3 concentric rings (template). The bulbs were wired together in series in groups of three with a corresponding resistor and then each bulbset wired in parallel to form the rings.
LEDs installed in acrylic mounting plate
Wanting to have the ability to select different lighting levels, I replaced the lamp’s original dimmer switch with a 3-way switch. The switch was then wired so that the first position would light the outermost ring, the second position would light the two outermost rings and the third position would light all three rings.
Everything went together as planned, however the results weren’t quite what I had hoped for. It turns out a 300 watt halogen bulb throws out quite a bit of light and, try as they might, my little LED bulbs came up a little short of replicating that output. Additionally, the temperature of the LEDs was much cooler than the halogen bulb and delivered the sensation of being under a fish tank light.
In spite of all of this, it was still a fun project and the lamp is currently serving duties in a guest room.