Slow fade-in circuit

OP said he wants a circuit considerably smaller than a matchbox.

I think the clearances required for 110VAC operation and the voltage ratings of the components you'll need to build a trailing-edge dimmer, say, are going to make that a problem if it all has to fit on a single board.

Why the circuit MUST fit inside the bell-housing of a ceiling fan is unclear if this is a one-off personal application, sounds more like someone trying to integrate something for sale.

Would recommend hiring an engineer in that case.

d while some come with dimmer

'Big surprise. It is easy enough to buy dimmable LED bulbs.

/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, requi ring the handle to move half it's range before the LED comes on at all, the n the brightness is irregular with movement of the control and even varies a bit while the handle is still.

ee some flickering of the light as it dims.

knowledge)

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 tu rned on. A VCO feeding a Triac / Diac pair should work, but I am unsure of details.

el, or

by... ignoring the electronic parts.

h a slowly charging capacitor that changes the duty cycle of a Triac.

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 i n a dimmed mode. The dimming will be purely transient coming up to full br ightness in a few seconds.

A 120 VAC circuit does not require any special clearances. That would be f or isolating high voltage and low voltage circuits. This entire design can be treated as a high voltage circuit.

It has to go in the housing of the fan so it isn't stuck someplace even mor e crowded like the wall switch box. That said, if a commercial product wou ld do the job, but not fit in a match box (as if that were remotely likely) it would be very reasonable to add a box next to the fan mounting box whic h could then house a commercial circuit more easily.

But it does seem reasonable to simply add a wall dimmer switch in place of the toggle switch. But maybe the lights are being brought up automatically by the "theater" system rather than manually switched on. The automatic e ffect would be nice though.

Enforcing some minimum distances between hot and neutral traces and any exposed contacts with hot and neutral on them seems like a good idea...resistors that are going to see the full rectified line voltage across them at some point should be rated for 350 volts

It's a weird requirement for a one-off

and while some come with dimmer

s. 'Big surprise. It is easy enough to buy dimmable LED bulbs.

ac/SCR type dimmers. I bought an LED ceiling light along with a dimmer whi ch was listed on the LED package as "compatible". It works very badly, req uiring the handle to move half it's range before the LED comes on at all, t hen the brightness is irregular with movement of the control and even varie s a bit while the handle is still.

see some flickering of the light as it dims.

my knowledge)

n my 12V LED strips lining the stair step in my theater. I already have wi fi 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.

anel, or

s by... ignoring the electronic parts.

ith a slowly charging capacitor that changes the duty cycle of a Triac.

re of the line voltage as well as the phase. A problem with many dimmers i s 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.

be for isolating high voltage and low voltage circuits. This entire design can be treated as a high voltage circuit.

more crowded like the wall switch box. That said, if a commercial product would do the job, but not fit in a match box (as if that were remotely lik ely) it would be very reasonable to add a box next to the fan mounting box which could then house a commercial circuit more easily.

of the toggle switch. But maybe the lights are being brought up automatic ally by the "theater" system rather than manually switched on. The automat ic effect would be nice though.

What's weird about it??? I can see someone wanting to not blow out their t heater experience by bringing up the lights abruptly. I get that.

There is a lot of home automation stuff on aliexpress, but you can never te ll just what it really does. They always push the Wow! factor rather than explaining it in any detail.

The ads are SO into color! Doesn't matter what it does, but it has to have color!!!

rk theater, suddenly turning on the lights is a somewhat unpleasant experie nce. 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.

triac type dimmers. I've read some articles about why this happens, but do n't recall the reasons. I think it comes down to the fact that LED supplie s don't naturally respond to changes in the AC duty cycle. So they have to measure the phase angle of the triac turn on and adjust the dimming from t hat. Since the full AC cycle is not presented to the supply the duty cycle is horrible.

LEDs. Direct control via a low voltage or resistance is the recommended me thod. But then this is an extra wire and a low voltage extra wire which mu st be run separately... in other words, a PITA.

Series capacitor makes a lot more sense than a resistance. No extra wire ne eded.

NT

I forget the original requirement details. An NTC thermistor could fade up some LEDs extremely simply.

NT

ez wrote:

dark theater, suddenly turning on the lights is a somewhat unpleasant exper ience. I want a simple circuit compatible with 110 volt dimmable LED light s that will slowly ramp the light output over a period of about 5 seconds o r so. I have found a number of simple designs that would work for 12VDC LE Ds, but none for 110VAC dimmable LED lights.

it

n triac type dimmers. I've read some articles about why this happens, but don't recall the reasons. I think it comes down to the fact that LED suppl ies don't naturally respond to changes in the AC duty cycle. So they have to measure the phase angle of the triac turn on and adjust the dimming from that. Since the full AC cycle is not presented to the supply the duty cyc le is horrible.

h LEDs. Direct control via a low voltage or resistance is the recommended method. But then this is an extra wire and a low voltage extra wire which must be run separately... in other words, a PITA.

needed.

Care to explain that in the context of my post? I was talking about using commercially available dimmer circuits. How are you talking of using a cap acitor? You mean to dim it only on application of power? Yeah, I suppose that could work, but it requires building a circuit which is to the many is sues of building a hobby circuit and adding it to a high voltage line.

t 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.

So I suppose I am dreaming when I look at this dimmer sitting in my hand th at is smaller than a pack of cards and can handle 600 watts? Or the one be low which handles 1000 watts AND includes WiFi?

Imagine showing up looking for free work and barking

No, but I did in the second post, and I apologized for not going into more detail.

I did not bark any orders. I just mentioned you did not bother to read what I wrote, which is tru

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.

eans like triac dimmers or a variac.

Who on Earth would employ a variac these days? I used plenty of them back when I was in college, but that was 40 years ago.

in the reverse sense to a triac. The circuit inside the lamp uses this clue to control the LED current.

A trailing edge dimmer can be used with CFL bulbs, yes, which leading edge dimmers normally cannot. It is true leading edge dimmers may not work as w ell as trailing edge dimmers with LED bulbs, but unless I am mistaken, I be lieve most consumer dimmers are leading edge dimmers, and they do work with dimmable LED bulbs well enough. I could use either one, although the 555 would need to be replaced with a passive solution, I think. It is the volt age control that has me a bit sytmied. A simple voltage divider is not a v ery good solution, since 130V at 20ma is 2.6 watts, whihc is going to get p retty hot in a small enclosure. Even when half-wave rectified, we are look ing at 1.3 watts, unless I use some sort of switching solution.

All of them I have seen with Arduino / Raspberry Pi inputs are PWM. That means something like a 555, which in turn means a low voltage DC supply. 'Possible, but a bit tricky given the space constraints.

That's right. There is already a WiFi fan control and light switch up in t he vell housing, so there isn't a whole lot of room.

'Not at all. The trailing edge dimmer circuit in te provided example has o nly 30 components. I can fit a lot more than that on a board less than 50m m on a side.

It must fit inside the bell housing because it has to be downstream of the switch. The switch - a wifi / Google Home controlled fan and light switch is in the bell housing. Running wires from the switch to the outside of th e light housing and back is not a very good idea.

No, I wasn't considering this as a salable item. I don't think it has enou gh sales potential to make it practical to produce commercially. I just wa nt it for the two ceiling fans in my theater.

I am an engineer. 'Not a EE, but I am an engineer, and this is certainly n ot beyond my capabilities.

Correct. Dimmers of up to 1000watts can easily fit in a case the size of a brownie.

That said, if a commercial product would do the job, but not fit in a match box (as if that were remotely likely) it would be very reasonable to add a box next to the fan mounting box which could then house a commercial circuit more easily.

Correct. A dimmer capable of handling up to 1000 watts can easily fit in a case smaller than a brownie.

Well, in this case, it is more a matter of needing to go inline between the switch lead and the light lead, both of which are in the bell housing.

That's possible, but not bery convenient. It's not the main issue, however.

Not when there is no toggle switch. The fan and light are entirely controlled wirelessly by the module in the bell housing. There is no switch box, at all.

Actually, they are being brought up by a Google Home Mini.

Manual fading would not be practical, really.

Yeah, I know that, too. This doesn't have to be ultra-fancy or ultra-smooth.

I would expect it to be stable once the light control reaches 100%. Until then, it needn't be perfectly stable, as long as it doesn't actually flash on and off.

You mean as it fades up? It won't be fading down, and with two light fixtures (two fans), some flicker will be less noticeable.

If a conventional triac based domestic dimmer will drive your lights then you could try adapting it a bit like this:

I haven't built this and it is only conceptual so some experimentation will be needed. It works like this: The diac/triac firing phase angle is determined by the time it takes for the voltage across CT to reach the diac trigger voltage, typically 20-30V. By robbing RT current from charging CT the add-on circuit can extend the firing delay without having to change RT. Finally because the voltage across CT is limited to

In more detail: D1-D4 can be 1N4148/914 etc. Q1-Q4 can be 2N3904/BC847 etc. C2 is the fade-up timing capactior probably several uF, as it charges via R4 it reduces the current sunk by Q3/Q4 to zero.

R1-3, C1, and Q1-2 ensure that C2 is discharged between uses. When the circuit is live Q1 is periodically switched on and keeps the C1 Q2 base node low. Q2 then plays no part in the fade-up ramp. When the power is removed R3 and Q2 discharge C2. After drawing the schematic I realized that the E-B junction of Q2 may be overly reverse biased so a diode in series with either the base or emitter may be wise.

As a start point R1-2-3-4 could all be about a megaohm, R5 about 5k, C1 about 0.1uF. D5 can be a low power 8-18V zener, as long as it is lower than the diac trigger volatge. It serves to ensure that even when Q3/4 are shunting phase timing current there is sufficient voltage to keep Q1 active.

Be interested to know if it actually works!

piglet

One slightly expensive solution is to swap the existing bulbs for smart ones and control them with an app. Then you can program the on-off time constants if you choose the right system.

Otherwise you basically want a soft start LED compatible trailing edge dimmer that has a time constant of 5s before it allows full mains cycles through. Your problem may well be that individual lamps do not present

A friend has burnt out several 240v trailing edge LED dimmers in a configuration that ought to work if the manufacturers were honest. The dimmer manufacturers have agreed to replace the failing duds free of charge which I take to be an admission of guilt.

e for isolating high voltage and low voltage circuits. This entire design c an be treated as a high voltage circuit.

n a case smaller than a brownie.

more crowded like the wall switch box.

the switch lead and the light lead, both of which are in the bell housing.

tch box (as if that were remotely likely) it would be very reasonable to ad d a box next to the fan mounting box which could then house a commercial ci rcuit more easily.

er.

of the toggle switch.

rolled wirelessly by the module in the bell housing. There is no switch bo x, at all.

system rather than manually switched on.

If you have a remotely controlled switch actuated by a smart device, why ca n't you just replace the smart switch with a smart dimmer and have the smar t controller manage the dimming? Are you saying you can't find those at al l? Is the switch an integral part of the fan?