Slow fade-in circuit...

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rhor...@gmail.com

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I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.
 
n Wednesday, September 23, 2020 at 2:08:15 PM UTC+10, rhor...@gmail.com wrote:
> I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

There is a fairly straight-forward solution, but it isn\'t going to be al that simple. You need to synthesise a 60Hz AC waveform that can move up to 110V RMS over 5 seconds.

The Baxandall Class-D oscillator lets you generate such an AC waveform fairly easily.

http://sophia-elektronica.com/Baxandall1959JM.pdf

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, which 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 have to pulse-width-modulate the DC you fed into it to get the five second ramp ramp you want.

The inductor is going to be a pretty effective low pass filter, so adjusting 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 microcontroller. 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 something 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 might take time.

--
Bill Sloman, Sydney
 
On 9/23/2020 12:08 AM, rhor...@gmail.com wrote:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.
Click to expand...

You can buy a \"DMX dimmer\" box off the shelf:

<https://www.amazon.com/American-Dp-415-Channel-Dimmer-Pack/dp/B000FVZUMM>

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, rhor...@gmail.com wrote:
> I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do. There are also different types of \"12VDC\" lamps, none of which (to my knowledge)
is a simple LED. You could, however, operate a servo motor to lower a shade over a panel, or
rotate a polarizer, i.e. ignore the electronic range of such devices by... ignoring the electronic parts.
 
On Tuesday, September 22, 2020 at 11:46:41 PM UTC-5, Bill Sloman wrote:
n Wednesday, September 23, 2020 at 2:08:15 PM UTC+10, rhor...@gmail.com wrote:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.
There is a fairly straight-forward solution, but it isn\'t going to be al that simple. You need to synthesise a 60Hz AC waveform that can move up to 110V RMS over 5 seconds.

The Baxandall Class-D oscillator lets you generate such an AC waveform fairly easily.
Modern versions use MOSFET switches, rather than the bipolar transistors, which 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 have to pulse-width-modulate the DC you fed into it to get the five second ramp ramp you want.

The inductor is going to be a pretty effective low pass filter, so adjusting 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 microcontroller. 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.
Click to expand...

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 small. This has to fit in the top bell of a ceiling fan, and one that already has a wifi controller in it. A \"standard\" dimmer circuit with the potentiometer replaced by a VCO should work without resorting to a large transformer.

> There are lots of other ways of doing it, and you can probably buy something 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 might take time.
 
> There are lots of other ways of doing it, and you can probably buy something 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 might 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
 
On Wednesday, September 23, 2020 at 12:29:14 AM UTC-5, bitrex wrote:
On 9/23/2020 12:08 AM, rhor...@gmail.com wrote:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

You can buy a \"DMX dimmer\" box off the shelf:

https://www.amazon.com/American-Dp-415-Channel-Dimmer-Pack/dp/B000FVZUMM

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.
Click to expand...

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 solutions, here. The unit needs to be smaller than a pack of gum - about the size if a Raspberry Pi Zero, and it only needs to slow the increase of the light intensity. Nothing else.
 
On Wednesday, September 23, 2020 at 12:39:09 AM UTC-5, whit3rd wrote:
LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do.
Click to expand...

I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. \'Big surprise. It is easy enough to buy dimmable LED bulbs.

There are also different types of \"12VDC\" lamps, none of which (to my knowledge)
is a simple LED.
Many are. As a matter of fact, I just installed a 12V wifi dimmer on my 12V LED strips lining the stair step in my theater. I already have wifi control 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 details.
Click to expand...

You could, however, operate a servo motor to lower a shade over a panel, or
rotate a polarizer, i.e. ignore the electronic range of such devices by.... ignoring the electronic parts.
Click to expand...
No, no, no. That is going off the rails. All I need is a circuit with a slowly charging capacitor that changes the duty cycle of a Triac.
 
On 23/09/2020 05:08, rhor...@gmail.com wrote:
I need a simple circuit design for a slow fade-in AC dimmer. In a
dark 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.
Click to expand...

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
 
El 23/09/2020 a las 6:08, rhor...@gmail.com escribió:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.
Click to expand...

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
Miguel Giménez
 
On Wednesday, September 23, 2020 at 4:22:12 AM UTC-5, whit3rd wrote:
On Wednesday, September 23, 2020 at 1:20:28 AM UTC-7, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 12:39:09 AM UTC-5, whit3rd wrote:
LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do.
I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. \'Big surprise. It is easy enough to buy dimmable LED bulbs.
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.

https://www.superbrightleds.com/moreinfo/led-panel-light/2ft-x-2ft-recessed-led-steel-troffer-light-40w-5000-lumens-dimmable/5837/

The dimmer input accepts a zero-to-ten-volt signal.
Click to expand...
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.
 
On Wednesday, September 23, 2020 at 4:39:52 AM UTC-5, Miguel Giménez wrote:
El 23/09/2020 a las 6:08, rhor...@gmail.com escribió:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

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
Miguel Giménez
Click to expand...
A microcontroller would present a number of problems, one of which would be supplying power. Although there are certainly solutions to provide 5VDC from 120VAC, they tend to take up a good bit of space. An analog device able to work directly from 120VAC is a better solution.
 
On 9/23/2020 7:01 AM, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 4:22:12 AM UTC-5, whit3rd wrote:
On Wednesday, September 23, 2020 at 1:20:28 AM UTC-7, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 12:39:09 AM UTC-5, whit3rd wrote:
LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do.
I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. \'Big surprise. It is easy enough to buy dimmable LED bulbs.
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.

https://www.superbrightleds.com/moreinfo/led-panel-light/2ft-x-2ft-recessed-led-steel-troffer-light-40w-5000-lumens-dimmable/5837/

The dimmer input accepts a zero-to-ten-volt signal.
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.
Click to expand...

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.
 
On Thursday, September 24, 2020 at 12:10:11 AM UTC+10, bitrex wrote:
On 9/23/2020 7:01 AM, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 4:22:12 AM UTC-5, whit3rd wrote:
On Wednesday, September 23, 2020 at 1:20:28 AM UTC-7, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 12:39:09 AM UTC-5, whit3rd wrote:
LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do.
I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. \'Big surprise. It is easy enough to buy dimmable LED bulbs.
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..

https://www.superbrightleds.com/moreinfo/led-panel-light/2ft-x-2ft-recessed-led-steel-troffer-light-40w-5000-lumens-dimmable/5837/

The dimmer input accepts a zero-to-ten-volt signal.
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.

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.
Click to expand...

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 than 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 components, and ones that can cope with that kind of power tend to be a bit on the bulky side.

--
Bill Sloman, Sydney
 
On 2020-09-23, rhor...@gmail.com <rhorerles@gmail.com> wrote:
On Wednesday, September 23, 2020 at 4:39:52 AM UTC-5, Miguel Giménez wrote:
El 23/09/2020 a las 6:08, rhor...@gmail.com escribió:
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

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
Miguel Giménez
A microcontroller would present a number of problems, one of which would be supplying power. Although there are certainly solutions to provide 5VDC from 120VAC, they tend to take up a good bit of space. An analog device able to work directly from 120VAC is a better solution.
Click to expand...

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!!!\"
 
On Wednesday, 23 September 2020 05:08:15 UTC+1, rhor...@gmail.com wrote:
> I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

Variac & microwave turntable motor.
At least if they already ran off a variac that would be one quick easy approach.


NT
 
rhor...@gmail.com wrote:
========================
I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.
Click to expand...

** So called \"Dimmable LEDs\" are not all the same nor dimmable by usual means 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 to control the LED current.

See fig 1 for a schematic of such a dimmer.

https://sound-au.com/project157.htm


..... Phil
 
On 9/23/2020 6:57 PM, Phil Allison wrote:
rhor...@gmail.com wrote:
=========================

I need a simple circuit design for a slow fade-in AC dimmer. In a dark 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.

** So called \"Dimmable LEDs\" are not all the same nor dimmable by usual means 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 to control the LED current.

See fig 1 for a schematic of such a dimmer.

https://sound-au.com/project157.htm


.... Phil
Click to expand...
These show some promise, the size seems good, it has the 0 to 10 volt
control. I have now idea what the impedance of

the 0 to 10 volt control is, so not sure how easy it would be to control
with an RC. Price is right.

Not sure how it reacts to applying AC with the control held at zero.

Might need a big resistor or see if these can be modified for 12V operation

https://www.1000bulbs.com/category/25-36-volt-hardwire-constant-current-led-drivers/
 12v-36v unit
https://www.1000bulbs.com/product/209386/HAT-10032.html
 Here\'s a 12V unit, but it\'s a little longer, 4.25\" x 1.5\".
Click to expand...

> https://www.1000bulbs.com/product/100980/LEDF-ACA12V12H10M.html

                                      Mikek


--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
 
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.
 
On Wednesday, September 23, 2020 at 4:20:28 AM UTC-4, rhor...@gmail.com wrote:
On Wednesday, September 23, 2020 at 12:39:09 AM UTC-5, whit3rd wrote:
LED fixtures that take 110VAC are all different types and designs, and while some come with dimmer
options, not all do.

I am aware, thanks. Non-dimmable bulbs do not work well with dimmers. \'Big surprise. It is easy enough to buy dimmable LED bulbs.
Click to expand...

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 the brightness is irregular with movement of the control and even varies a bit while the handle is still.

In your application this will mostly not be an issue although you may see some flickering of the light as it dims.


There are also different types of \"12VDC\" lamps, none of which (to my knowledge)
is a simple LED.
Many are. As a matter of fact, I just installed a 12V wifi dimmer on my 12V LED strips lining the stair step in my theater. I already have wifi control 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 details.

You could, however, operate a servo motor to lower a shade over a panel, or
rotate a polarizer, i.e. ignore the electronic range of such devices by.... ignoring the electronic parts.
No, no, no. That is going off the rails. All I need is a circuit with a slowly charging capacitor that changes the duty cycle of a Triac.
Click to expand...

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 brightness in a few seconds.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209
 
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