CF Lightbulb Dimmer
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From: Bob Masta on 26 Mar 2010 09:28 On Fri, 26 Mar 2010 00:05:37 +0100, "petrus bitbyter" <pieterkraltlaatditweg(a)enditookhccnet.nl> wrote: > >"David Eather" <eather(a)tpg.com.au> schreef in bericht >news:B_CdnZCuHfDdeDbWnZ2dnUVZ_tOdnZ2d(a)supernews.com... >> No, not phase control. The MOC3041 is a zero crossing triac opto coupler. >> This would work as the OP suggested - by subtracting mains cycles e.g. 4 >> cycles on 1 cycle off or 3 cycles on 2 cycles off. >> >> Would it work to dim a CF bulb. I don't know, but I don't think so. > >Ever build a heat controller like that. Even an incandescent bulb started to >flicker below 60-70%. This method is definitively not the way to dim lights. <snip> I built a kiln controller using a zero-crossing triac optocoupler, and at low duty cycles you could see flicker in other incandescent lights in the house! Best regards, Bob Masta DAQARTA v5.10 Data AcQuisition And Real-Time Analysis www.daqarta.com Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, FREE Signal Generator Pitch Track, Pitch-to-MIDI DaqMusic - FREE MUSIC, Forever! (Some assembly required) Science (and fun!) with your sound card!
From: John Fields on 26 Mar 2010 11:28
On Thu, 25 Mar 2010 21:38:28 -0700 (PDT), Bret Cahill <BretCahill(a)peoplepc.com> wrote: >> >> >> >Just start subtracting cycles. �Below 25% - 40% power it'll start to >> >> >> >flicker. >> >> >> >> >Bret Cahill >> >> >> >> Subtracting cycles? >> >> >> >Instead of flashing 60 or 120 Hz it only flashes 30 or 60 cycles/sec. >> >> >> >Eventually everyone will go to LED which is easy to operate at half >> >> >power: �add a half bridge rectifier. >> >> >Or maybe the LED itself is a half bridge rectifier. --- Half _wave_ rectifier --- >> Only if the AC supply voltage is low. LEDs don't like to be zenered. > >You can take out the blue LED from a dollar store night light and wire >up 4 - 6 whiteish LED Christmas lights and then hot melt glue the >string to the wall. --- Mmmm. stylish... --- >I'm guessing the power consumption is still about 1/4 watt -- not >worth turning off. --- Hmmm... In one breath you demand green, and then in the second you say that wasting 1/4 watt is unimportant. For someone who pretends to be interested in the "big picture" it seems you've lost sight of the fact that if one hundred million of those widgets were to be left on all the time and they were dissipating 1/4 watt each, they'd dissipate 25 megawatts, of which 12.5MW would be wasted if the illumination was only needed for an average of 12 hours. So there's 12.5MW up in smoke... Then there's the matter of keeping the magic smoke _inside_ the LEDs, which will be difficult since, as Larkin pointed out, LEDs don't like to be Zenered. One way to fix that problem is to configure the LEDs as two series strings connected in parallel opposition, like this: (View in Courier) 120AC>---[R]--+-[LED>]---[LED>]---[LED>]-+ | | +-[<LED]---[<LED]---[<LED]-+ | 120AC>-----------------------------------+ That way, the OFF LEDs only see the Vf of the ON LEDs instead of the entire mains peak voltage across them. I'd use 6 LEDs total to keep everything symmetrical, and then, since only 3 LEDs would be on at a time they'd dissipate: 10.5V * 0.02A P = --------------- = 0.105 watts 2 and for both strings that would be 0.210 watts, pretty close to your 1/4 watt guess. The series current limiting resistor also has to be considered if the kluge is going to live past the first mains cycle in, and its value will be: Vmains - Vled 120V - 10.5V R = --------------- = -------------- = 5475 ohms Iled 0.02A Unfortunately, it'll dissipate: P = I�R = 0.02�A * 5475 ohms = 2.19 watts, so there's a whopping 219 MEGAwatts wasted as heat. Assume then that these kluges will only need to be on about half the time, on average, and the waste will be about 116 megawatts if they're left on all the time. --- >I have very little credibility in interior design. You'd have to get >some personality like Martha Stewart to get it to sell. --- With as little credibility as you have, period, I doubt whether _anyone_ would want to besmirch their good name by having it associated with the likes of you. JF |