LED Lightbulb

28 Nov 2008

LED Lightbulb

For Christmas last year I bought my Dad an LED lightbulb to replace the incandescent lightbulb in his work flashlight. The incandescent bulbs kept breaking whenever he smacked it against a pipe or a wall (he's a plumber) and at a couple bucks a pop he found himself spending a lot of money on lightbulbs. The LED lightbulb I bought him seemed like a great solution. It was a little pricey but I figured it would last a long time and totally be worth the price. One bulb would last longer than a couple traditional incandescent bulbs. However, the LED bulb didn't last more than a couple months before the lights started flickering.

I figured the schematic on the circuit board wasn't designed very well and so I gave it shot myself. I designed a new circuit board, four strings of five LEDs in parallel each with a 68 ohm resistor (four in total). I calculated the input voltage from the total charge of the battery, approx 20 volts, and used a nifty LED calculator online. So far so good. The light isn't quite as bright as I would have hoped but luckily BatchPCB threw in an extra board so I can do a test with some brighter LEDs.

LED Lightbulb

In case you were curious, it was installed into a 18V Ryobi battery powered flashlight (the battery pops into a hand drill, hand vacuum, electric saw, etc.). I soldered long, thin male headers to the power and ground leads of the circuit board and used a custom bulb base from the older broken bulb that accepted these headers. For the next bulb, I'll have to cobble together something different.

LED Lightbulb

Here are the Eagle files for the LED lightbulb: ledlightbulb_eagle.zip