I need a simple circuit design for a slow fade-in AC dimmer. In a dark the ater, suddenly turning on the lights is a somewhat unpleasant experience. I want a simple circuit compatible with 110 volt dimmable LED lights that w ill slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but none for 110VAC dimmable LED lights.
n Wednesday, September 23, 2020 at 2:08:15 PM UTC+10, snipped-for-privacy@gmail.com wro te:
eater, suddenly turning on the lights is a somewhat unpleasant experience. I want a simple circuit compatible with 110 volt dimmable LED lights that w ill slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but n one for 110VAC dimmable LED lights.
There is a fairly straight-forward solution, but it isn't going to be al th at simple. You need to synthesise a 60Hz AC waveform that can move up to 11
0V RMS over 5 seconds.The Baxandall Class-D oscillator lets you generate such an AC waveform fair ly easily.
It's usually used at frequencies above 60Hz, but the kind of centre-tapped power transformer you'd need is easily available for 60Hz operation.
Modern versions use MOSFET switches, rather than the bipolar transistors, w hich were all that was available when Baxandall wrote the paper.
You'd need a fairly high current choke to feed the centre tap, and you'd ha ve to pulse-width-modulate the DC you fed into it to get the five second r amp ramp you want.
The inductor is going to be a pretty effective low pass filter, so adjusti ng the width of string of pulses in a 1kHz pulse stream would be all you'd need to do, and your could do that with a very simple and cheap microcontr oller. That would be 5000 pulses, so the "on" period would go up by 0.2usec from pulse to pulse. That implies a timing clock that's running at 5MHz or faster, which wouldn't be hard to get.
There are lots of other ways of doing it, and you can probably buy somethin g off the shelf - there's lots of stuff available for theater lighting and that's been true for many years - but finding something small and cheap mig ht take time.
-- Bill Sloman, Sydney
You can buy a "DMX dimmer" box off the shelf:
paired with a control box (or PC interface) you can set up fade in/out programs synced to external triggers as you like. DMX is a communications standard for theater and stage lighting control.
On Tuesday, September 22, 2020 at 9:08:15 PM UTC-7, snipped-for-privacy@gmail.com wrote :
eater, suddenly turning on the lights is a somewhat unpleasant experience. I want a simple circuit compatible with 110 volt dimmable LED lights that w ill slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but n one for 110VAC dimmable LED lights.
LED fixtures that take 110VAC are all different types and designs, and whil e some come with dimmer options, not all do. There are also different types of "12VDC" lamps, non e of which (to my knowledge) is a simple LED. You could, however, operate a servo motor to lower a sha de over a panel, or rotate a polarizer, i.e. ignore the electronic range of such devices by... ignoring the electronic parts.
rote:
theater, suddenly turning on the lights is a somewhat unpleasant experience . I want a simple circuit compatible with 110 volt dimmable LED lights that will slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but none for 110VAC dimmable LED lights.
that simple. You need to synthesise a 60Hz AC waveform that can move up to
110V RMS over 5 seconds.irly easily.
which were all that was available when Baxandall wrote the paper.
have to pulse-width-modulate the DC you fed into it to get the five second ramp ramp you want.
ing the width of string of pulses in a 1kHz pulse stream would be all you'd need to do, and your could do that with a very simple and cheap microcontr oller. That would be 5000 pulses, so the "on" period would go up by 0.2usec from pulse to pulse. That implies a timing clock that's running at 5MHz or faster, which wouldn't be hard to get.
I'm sorry, I should have provided more details. First of all, this is for a home theater, not a public performance / movie theater. It doesn't need to drive a lot of power: maybe 50 watts @ 120V. Secondly, it needs to be s mall. This has to fit in the top bell of a ceiling fan, and one that alrea dy has a wifi controller in it. A "standard" dimmer circuit with the poten tiometer replaced by a VCO should work without resorting to a large transfo rmer.
ing off the shelf - there's lots of stuff available for theater lighting an d that's been true for many years - but finding something small and cheap m ight take time.
I have been looking, and there are a number of off-the-shelf 12VDC solutions for small LEDs, but I have found nothing, yet for 120VAC
theater, suddenly turning on the lights is a somewhat unpleasant experience . I want a simple circuit compatible with 110 volt dimmable LED lights that will slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but none for 110VAC dimmable LED lights.
See above. This is not for stage lighting. As it happens, I am extremely familiar with DMX as well as PixelNet and ArtNet. These are not good solut ions, here. The unit needs to be smaller than a pack of gum - about the si ze if a Raspberry Pi Zero, and it only needs to slow the increase of the li ght intensity. Nothing else.
ile some come with dimmer
I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. 'Bi g surprise. It is easy enough to buy dimmable LED bulbs.
wledge)
Many are. As a matter of fact, I just installed a 12V wifi dimmer on my 12 V LED strips lining the stair step in my theater. I already have wifi cont rol of the ceiling lights. I just need them to come up slowly when turned on. A VCO feeding a Triac / Diac pair should work, but I am unsure of deta ils.
or
. ignoring the electronic parts. No, no, no. That is going off the rails. All I need is a circuit with a s lowly charging capacitor that changes the duty cycle of a Triac.
No, that's not the only option; you can get LED light fixtures that accept low-voltage controls, and safely wire in something that does the brightness slew limiting that you want.
The dimmer input accepts a zero-to-ten-volt signal.
Why don't you just get a standard mains dimmer compatible with your dimmable lights and remember to wind the wick up slowly. It doesn't need to be an automatic ramp up if you are the only one using it.
-- Regards, Martin Brown
We did that many years ago with a small microcontroller and a triac, it worked very well. The application was sunrise/sunset simulation in a city small-scale model.
-- Saludos
You are not reading what I wrote. These are CEILING FANS in a HOME THEATER. Alternate fixtures are not an option; they are part of the ceiling fan. The dimmer must be considerably smaller than a matchbox so it can fit in the bell housing.
rote:
theater, suddenly turning on the lights is a somewhat unpleasant experience . I want a simple circuit compatible with 110 volt dimmable LED lights that will slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, but none for 110VAC dimmable LED lights.
A microcontroller would present a number of problems, one of which would be supplying power. Although there are certainly solutions to provide 5VDC f rom 120VAC, they tend to take up a good bit of space. An analog device abl e to work directly from 120VAC is a better solution.
Wow, what a pain in the ass. Guy said nothing about ceiling fans in the original post. Imagine showing up looking for free work and barking orders simultaneously. Wanna bark orders at least have the decency to pay someone for the privilege.
IOW get a grip, pal.
nd while some come with dimmer
'Big surprise. It is easy enough to buy dimmable LED bulbs.
cept low-voltage controls, and safely
.TER. Alternate fixtures are not an option; they are part of the ceiling fan . The dimmer must be considerably smaller than a matchbox so it can fit in the bell housing.
It's rather unrealistic ambition. He wants to control ten watts or more at
110V AC - about 100mA - and wants the whole thing in a package smaller th an a matchbox, and simple with it. You can get quite a lot of surface mount components into that sort of volume, but it would need some reactive compo nents, and ones that can cope with that kind of power tend to be a bit on t he bulky side.-- Bill Sloman, Sydney
NTC thermistor, as used to soft-start projector lamps and such.
(It'll get hot in a ceiling rose, set it on fire and burn the house down, but that wasn't covered in the spec either :)
-- Ian "Tamahome!!!" - "Miaka!!!"
heater, suddenly turning on the lights is a somewhat unpleasant experience. I want a simple circuit compatible with 110 volt dimmable LED lights that will slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, bu t none for 110VAC dimmable LED lights.
Variac & microwave turntable motor. At least if they already ran off a variac that would be one quick easy appr oach.
NT
snipped-for-privacy@gmail.com wrote: =========================
heater, suddenly turning on the lights is a somewhat unpleasant experience. I want a simple circuit compatible with 110 volt dimmable LED lights that will slowly ramp the light output over a period of about 5 seconds or so. I have found a number of simple designs that would work for 12VDC LEDs, bu t none for 110VAC dimmable LED lights.
** So called "Dimmable LEDs" are not all the same nor dimmable by usual mea ns like triac dimmers or a variac.Most are designed to use a "trailing edge dimmer" that chops the AC wave in the reverse sense to a triac. The circuit inside the lamp uses this clue t o control the LED current.
See fig 1 for a schematic of such a dimmer.
.... Phil
Maybe hack one of the commercial triac AC dimmers? I get a ton of hits for DIY triac dimmer. (lots with Arduino input.) I didn't look at the details.
George H.
while some come with dimmer
Big surprise. It is easy enough to buy dimmable LED bulbs.
Even dimmable LED bulbs don't always respond well to the standard triac/SCR type dimmers. I bought an LED ceiling light along with a dimmer which was listed on the LED package as "compatible". It works very badly, requiring the handle to move half it's range before the LED comes on at all, then th e brightness is irregular with movement of the control and even varies a bi t while the handle is still.
In your application this will mostly not be an issue although you may see s ome flickering of the light as it dims.
nowledge)
12V LED strips lining the stair step in my theater. I already have wifi co ntrol of the ceiling lights. I just need them to come up slowly when turne d on. A VCO feeding a Triac / Diac pair should work, but I am unsure of de tails., or
... ignoring the electronic parts.
slowly charging capacitor that changes the duty cycle of a Triac.
Good luck with that. I believe I would use an 8 pin MCU which is aware of the line voltage as well as the phase. A problem with many dimmers is the poor response to line voltage changes, but then you won't be using it in a dimmed mode. The dimming will be purely transient coming up to full bright ness in a few seconds.
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