Slow fade-in circuit...

[rhor...@gmail.com]

On Thursday, October 1, 2020 at 4:17:49 AM UTC-5, piglet wrote:

We haven\'t mentioned RFI yet but switching at a few hundred Hz into the
building wiring could be a potent source of radio interference. I don\'t
know what your site needs are but it may be prudent to allow for some
inductance and filter caps needed somewhere.

At less than a 1/4 ampere load, I\'m not expecting much of a problem, especially not up around 2 - 5 GHz, which is where most of the electronics in the room operates. The impedance of the MOSFET I chose is 0.86 Ohms - perhaps I could choose one with a higher impedance and thus a lower slew rate, resulting in lower frequency harmonics. The leads will be about 1/4 of a meter, giving them an inductance of less than 500 microHenries - pretty insignificant at moderate RF frequencies, so a coil would not hurt. That said, a filter cap across the MOSFET of about 200 pF or so should quiet the noise well enough, I think, if it is even needed at all.

BTW, although the detector and the amp are rated at 7V, the comparator is listed at 5.5V max, so I went with a 5.6V Zener, rather than 6V. It\'s still pretty tight, but it should give a little more margin, just in case. I don\'t want to have to be replacing these every couple of years.

 

[rhor...@gmail.com]

On Thursday, October 1, 2020 at 7:25:21 AM UTC-5, Clifford Heath wrote:

On 1/10/20 6:56 pm, rhor...@gmail.com wrote:
On Thursday, October 1, 2020 at 1:45:51 AM UTC-5, piglet wrote:
If you go to very large C1 like 10 or 22uF then I wonder if that is too

I expect not. 2.2uF + 100M gets me very close in the sim. I don\'t expect to be an order of magnitude off, and with leakage on the order of a few pA, I should be able to increase R1 to nearly a Gigaohm.
How are you going to protect the PCB from moisture and accumulated
conductive cruft? The leakage into the op-amp isn\'t likely to be your
limit, not for very long anyhow.

I\'d go with lower impedance and bigger capacitors.

That gets into other issues, like higher operating currents - a real problem for this tiny power supply.

I intend to coat the high impedance section with lacquer. Corona Dope should work. With a dielectric strength of around 20 KV / mm, I could use a layer of Epoxy, too. I will keep the high impedance components well isolated and separated. Encase them in a block of epoxy, and the environment is no longer an issue. There are only three of them, after all. In any case, 100M is not all that excessively high. If it were over 10^10 Ohms, I would be far more concerned, but 10^8 doesn\'t require highly specialized treatment, really. I did mention earlier I don\'t want to exceed 10^9, and I won\'t. Well, I shouldn\'t have to, anyway.

 

[Tony Stewart]

On Wed. 23 Sep.-20 10:53 a.m., Bill Sloman wrote:

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.

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.

In 1971 my pal who was also an EE student, designed and built a hand
proximity dimmer using up/downcounters with hand wave duration step size
in 3 steps or continuous with 256 steps in a 2 second. The counter value
was then converted to phase angle in a non-linear fashion to linearize
intensity for controlling the Triac. If you are driving only LED\'s and
the dimmer fails due to leakage currents, the std fix was to add a 8W
bulb which acts as a ~60W gradient load at low levels due to thermal
resistance to shunt leakage currents. It would detect an rapid hand
wave at 1ft away and like the Star Trek door effect. Or nowadays the
Walmart door experience. This is all trivial Logic design and used a
small hand-wound pulse transformer for isolation to the touchpad that
acted as an antenna. The signals used for proximity were in the xx kHz
range.

But rather than an inverter a phase controlled Triac can work well if
the AC LED bulb is dimmable.

Tony.

 

[rhor...@gmail.com]

I cleaned up the design a bit:

<http://siliconventures.net/images/Ramp.PNG>

Here are the board designs:

Top
<http://siliconventures.net/images/Ramp%20Board%20Top.PNG>

Bottom
<http://siliconventures.net/images/Ramp%20Board%20Bottom.PNG>

Top Copper Only
<http://siliconventures.net/images/Ramp%20Board%20Top%20Copper.PNG>

Bottom Copper Only
<http://siliconventures.net/images/Ramp%20Board%20Top%20Copper.PNG>

This is curious. There seems to be a birdy right at 0.8 seconds. I investigated a little, and it looks to be real. This will produce a little flicker just before 1 second is elapsed, but I don\'t think that will be a show-stopper:
<http://siliconventures.net/images/Trace%20Analysis.PNG>

 

[rhor...@gmail.com]

On Friday, October 2, 2020 at 5:50:21 AM UTC-5, Anthony Stewart wrote:

In 1971 my pal who was also an EE student, designed and built a hand
proximity dimmer using up/downcounters with hand wave duration step size

That\'s a neat idea. Just a few years later than that I was asked to design a power supply for a superconducting solenoid. It had to provide 0 - 1000 amperes at 0.0 - 0.75 VDC reproducible to within 0.001 ampere over a minimum time frame of 6 months. It had to be able to ramp the current over a period of as much as 2 weeks. I used an LF356 with an oil-filled capacitor that cost $200 - in 1980 dollars, mind you - to create the ramps.