Dimming LED bulbs designed to replace halogen lamps

dimming-led-halogen-replacementsHalogen bulbs put out a lot of focused light but they do it at the expense of burning up a lot of Watts and generating a lot of heat. The cost for an LED replacement like the one seen disassembled above has come down quite a bit. This drove [Jonathan Foote] to purchase several units and he just couldn’t resist tearing them apart to try out a couple of hacks.

The one we find most interesting is a PWM based dimming hack he pulled off with an Arduino board and a FET. The bulbs are designed to be dimmable through the 12V supply that feeds the light fixture. But the relationship of dimmer position to light level is not linear and [Jonathan] figured he could do better. His solution is to add a FET in parallel with the LEDs. When activated it basically shunts the current around the diodes, resulting in a dimming. The video below shows this in action. We wonder if the flashing is a camera artifact or if you pick that up with your eye as well?

You may also be interested to read his post on Gelling the LED bulbs. Gels are colored filters for lights (or camera lenses). He cuts his preferred color down to size and inserts it between the LEDs and the lenses.

[Read more...]

AVR light controller

halogen

[Matthias] sent us this project where he builds an AVR light controller. He had a halogen bike light laying around, but was unsatisfied with its lead-acid battery. He wanted to use a lithium-polymer battery but found that they can’t be used directly with halogen lamps due to their voltage. His produced 8.5 volts at full charge and can’t be discharged to below 5 volts. He new a power controller would be necessary to try to flatten that out for his lamp, which needed to stay between 6-12 volts.

He used an ATtiny45 doing PWM to change the voltage. Some other cool features he added were the high and low settings and an LED status light for warnings. You can find pictures, schematics and source code on his page as well as tons of great information. Great job [Matthias].

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