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[on:]

Hi,
I'm interested in making my own LED light bulb fixtures to replace incandescent bulbs. however i cant seem to find any documentation that explains the internal of the bulbs. theoretically it should be very simple, just a small switching regulator for the 120vac to the 12vdc for the led array but i can find anywhere that confirms this. So my questions are these:
1) does it actually use a switching supply or just rectify the AC signal and use that?
2) if i connect the 12v rail to the transistor and optoisolator to an arduino should I be able to control them with a simple analogwrite command?
3) should a couple of simple 3000k super bright leds work?

Thank you very much for any replies!!

[Reply #1 on:]

1)  http://en.wikipedia.org/wiki/LED_lamp#LED_light_bulbs   
was wikipedia too obvious? ;-)

2) i think so

[Reply #2 on:]

i cant seem to find any documentation that explains the internal of the bulbs.

I don't know how they work, and it's not something I would be tempted to experiment with myself because of the inherent dangers of working with mains voltages. If you can come up with a solution that uses a commercially manufactured sealed power supply to bring the mains voltage into a safe range for your LED control system that would be fine, but if you're thinking about building your own enclosure combining mains voltages and electronics then in my opinion that's dangerous and introduces a significant risk of electrocution and fire hazard.

To put it another way - if you knew enough about the subject to understand the risks and tackle it safely - you probably wouldn't be here asking us how they work.

[Reply #3 on:]

im not too worried about working with 120vac as we work with this stuff and much much higher in the lab all the time.  my actual short coming is with the lower voltage supplies.  what i was sort of hoping to hear was that you could simply rectify the ac to dc, filter it, then run it through a buck converter for the (120/sqrt(2))-->5vdc conversion.

but maybe this would be just too simple and thats not allowed :/

[Reply #4 on:]

You never want to control a LED with voltage only; once you reach the forward voltage of the LED (Vf) the current starts to ramp up very quickly with very small increments in voltage. A LED should always use a current controlled supply if you want reliability.

I'd suggest poking around on eBay for an AC LED driver; they're so cheap it's impossible to beat them with a DIY approach.

[Reply #5 on:]

im a little consused what the led driver accomplishes and its composition.
what i originally imagined doing was something like the led fader demo in arduino but on a larger scale, why shouldn't this be achievable?

[Reply #6 on:]

i guess u still didnt read the wikipedia link...

Light-emitting diodes use direct current (DC) electrical power. To use them on AC power they are operated with internal or external rectifier circuits that provide a regulated current output at low voltage. LEDs are degraded or damaged by operating at high temperatures, so LED lamps typically include heat dissipation elements such as heat sinks and cooling fins.

thats for 230V


maybe you can read this with google translate, there is some info
http://www.mikrocontroller.net/articles/LED-%22Birnen%22

[Reply #7 on:]

thanks for that

from what i understand, they are first rectifying the HV AC lines and then running it through a simple zener diode to drop the voltage down to 30VDC for the LEDs?  If so then this is good news since this can easily be controlled via a mosfet and optocoupler connected to an arduino with digital write