But when i started measuring the bulb (3.5w) i found that only in 1 direction i found about 5M of resistance, from which i came to the conclusion that it is actually a DC-Bulb running on 110-120v
Now that would make the whole thing a lot easier to do, no need for zero-crossing detection, just PWM driven should work.
QuoteNow that would make the whole thing a lot easier to do, no need for zero-crossing detection, just PWM driven should work.No it won't.
in fact there do exist dimmer boards that take PWM input. I think the have an ATtiny on board (could be another controller), which reads the PWM input and then handles the zero crossing and phase cutting part.
Ha they have changed the meaning of the word filament. In fact that is a filament "effect" bulb not actually a filament bulb.
Now does anyone think PWM dimming will work in between then extra rectifier bridge and the bulb ?
If the bulb is quoted as "dimmable" in its specification, you need to use phase control dimming. So get back to your zero-crossing detector and Triac controller with opto-isolators.
Possibly. At 500 Hz it might work, no faster.
Now what are you going to use to switch it?
And your Subject heading is misleading. It is a 220 V bulb.
I will the parts are on the way i do need to sort this out one day, the issue i am foreseeing is that since i want to receive DMX to determine dimming i will have 2 interrupts going and i figure it may be easier to program the PWM dimming in combination with that.
what makes you say that the use of an opto-coupler would limit the speed a tad i suppose, my concern is actually that the 100Hz phase cutting may cause flicker but is suppose i could put a rectifier-bridge and a capacitor afterwards.
Well i am far from sure, the high voltage is an issue to be considered mainly and a bit of googling pointed me towards a BU406. If i put the rectifier bridge followed by a fair size capacitor(high voltage of course), drive the BU406 with an opto-coupler circuit (PC817 should do) from a PWM output and put another capacitor between the BU406 and the bulb, then am i overlooking something ? (probably.. )
Ah yes sorry, but i am intending to drive it with 110v DC, i will correct that, it is sold as a 220 AC but since it has a rectifier bridge in there it is actually both.
Not sure where the interrupts have to do with DMX
A dimmable bulb presumably contains a switchmode down-converter operating at a high frequency - many kilohertz in general. The higher the frequency the smaller and cheaper the inductor and capacitors though the switching transistor and diodes must be capable.
So you drive the BU406 via a PC817 which is nominally rated up to 80 V as maximum. Where are you going to get this driving voltage?
How will you put another capacitor between the BU406 and the bulb? In series? How would that work? Can't put it in parallel.
BU406 sounds plausible. 5 Amps should be way more than 5 LED bulbs will draw
What has the rectifier bridge got to do with it? 220 V is 220 V, AC or DC (actually, the peak of 220 AC to which the capacitor charges is more like 310 and that is only if it is 220 and has not floated up to 250 V). It does not become 110 because you rectify it.