Controling Holiday Lights

There you go again ;-)

Powering lamps designed for 120VAC with rectified 170 VDC (= 170 VRMS) as you suggest is problematic because if the circuit were to ever stop chopping, the lamp would burn out right quick.

So when MOSFETs are used as the dimming control elements for lamps with an AC power source, the lamps are powered by AC, *not* DC. (and the circuit is elegant, not "ugly", in my personal opinion).

It isn't any harder to do it right; it requires the essentially the same components as what you suggest and so is not intrinsically "more expensive" as you claim.

... Marc Marc_F_Hult

And in the case of TRIAC based dimmers, it would be handy for you to see the underlying equations so that you would know that what you claimed in this newsgroup in umpteen posts simply does not work and that despite your claim to the contrary, there is in fact an "easily calculable relationship to dim level". See my the equations in the url in the line below.

Here sylvan snips out the part of my sentence above that makes his quip above so silly and relates to the critical importance of timing, namely:

*IF* one also knows when the zero crossing occurs as is conventional. sylvan doesn't know the z-crossing and so futilely tries/d to overcome that lack of critical data .."

He fantasized that with complex waveforms and (newsgroup post by newsgroup) increasing frequencies and complexity, he could make a TRIAC dim evenly without skipping half-cycles and without a timing reference to the zero-crossing. But he couldn't despite the fact that he claimed that he had.

I don't. You gave up using the 18.2 timer. Then you gave up trying to time using progressively higher and higher frequencies. Then you finally broke down and kinda hint that you would have to time it with reference to the zero-crossing because no matter how what kilo/mega/gigahertz frequency you tried, it didn't work. "Timely". Read what I wrote because it is at the core of why what you have written flat out does not work. I thank you kindly for getting that part right finally and ending your obfuscation. When you finally stop dodging and misquoting, it will be easier to know what you actually mean to say.

Of course it is. When one compresses an 8-bit linear curve to a 4-bit square-law curve, one uses fewer bits and incorporates the non-linear way in which humans perceive light. This is an excellent example of perceptual coding (square-law curves) that has been around for decades.

Why don't I ? Do you think that log is intrinsically better than linear? For what purpose? A linear curve is in fact one of the conventional choices in quantitatively calibrated commercial dimmers. See the AL4016 dimmer chip at

that I cited previously.

Huh? WHAT is "human perception"? Having spent many years with densitometers and calibrated light meters, and different films and developers and toners and papers, I can assert unequivocally that a strict log curve is *not* what is always aesthetically pleasing or convincing or realistic or desired in part because of the time-dependence of the logarithmic human perception of light.

Perhaps if you were more knowledgeable, you would write that a different, equally valid, also quantitative, also commercially available curve, that incorporates a different approximation to the way humans perceive light, is one that obeys a square-law, such as the AL4017 chip -- also available from

Lower than what? Lower than the basic physics of electron flow that you got flat out wrong?

If you know the physics, and can write and use the equations, the "perceptual coding" could in fact be done at the last moment, on the fly, by choosing a different equation or coefficient immediately before sending the ON instruction to the TRIAC.

I can transform the curves shown in my spreadsheet into most any curve that is wanted: log, square-law, linear, s-shaped, and any combination of them. I can do this despite the fact that you have asserted that there is no ready mathematical relationship, because you are also wrong when you assert that.

And practical dimmer curves often follow more than one 'law' for practical reasons. One common need is for a preheat-level that can be incorporated into the curve. In my case, I want a flat part at the top of the voltage curve to close the contact of a mechanical relay in order to effectively switch the TRIAC out of circuit at 100% on and I want that to be an un-missable target when physically rotating a knob or moving a slider.

Similarly with the bottom of the curve. I do *not^ want a barely visible low level (i.e, the logarithmic curve you insist I should want) in a real light source in a real room because with incandescent lights, that is inordinately wasteful of electricity.

So I do *not* want a log curve at low levels as you insist I should. It is much more efficient to switch to a lower wattage lamp for low levels and it is an outright requirement if one wants anything resembling 'white" (not orange) light using incandescent lamps.

I realize, you realize, he, she, or it (Already!) realizes.

Duh ... That's what effectively part of what a square-law dimmer curve addresses. So what you are saying is that you would prefer a AL4017 over a AL4016.

You pontificate in a way that makes it appear that you don't realize that folks accomplished and have made commercially available long ago what you are still grappling with in theoretical terms while using smoke and mirrors to avoid the reality that your dimmer design flat out doesn't work because you are ignorant of the basic physics.

Seems to me that you have interesting ideas that are usefully discussed in this newsgroup. Thank you for that.

But do try to learn something in the process and do help us fix mistakes or misstatements rather than trying to cover them up.

Take care ... Marc Marc_F_Hult

You misunderstand.

120vac sine wave == about +/-170v peak. I was not suggesting creating a filtered 170vdc supply, just rectifying the 120vac sine wave.

You won't need a chopper, because it isn't pure D.C. steady at 170v, it is just the lower (negative going) half of the wave flopped into the gaps on the top. Still goes up to 170v and down to 0v, 120 times per second, it just no longer alternates, hence it is D.C. (pulsating).

So my Athlon 64 is powered by A.C. because I plug it into an A.C. power source? Sure, in some sense, but not practically correct. Put a scope on the power leads, the Athlon is definiteliy powered by D.C. and if you rectify the incoming A.C., you no longer have A.C.

It is only A.C. if it alternates polarity. That is what Alternating Current means.

sdb

[a bunch of innuendo and lies wrapped around a strawman that I supposedly said I wanted log curve after Marc supposedly did not say he wanted equal intensity steps]

This is truly hopeless. It is also rather funny that you bring a densitometer and film and toners and papers into this thread after I just spent a week with Dr Hunt (no, I'm not on a first-name basis with him, maybe you are). It is not even funny how much I got from a lunchtime 5 minute conversation with him re. light and color reproduction, vs how much time I've spent repeating myself for you.

But hey, you did a lot better at this than would I at hydrology!

sdb

hmmm ... We don't understand each other, do we?

Here's one conventional way organizing what we have been discussing:

1) Real World System, represented by ---> 2) Conceptual Model of real world (typically a simplification) ---> 3) Simulation Model ---> 3a) Mathematical Model(exact or approximate) typically as equations AND(OR) 3b) Physical Model 4) Solutions 4a) Math: Numerical results (often themselves approximations) AND(OR) 4b) Physical: Observed results 5) Applications,typically choosing from a range of legitimate solutions (4a,4b) which are typically approximations of the Real World (1)

The solutions (4a) and(or) (4b) can be compared to the Real World (1) to assess how close they are to reality. How close is "close enough" depends on the objective (purpose), is often subjective, and is assessed in Applications(step 5).

We are in agreement through step (1) ( I think ;-)

My Conceptual Model (2) of the physics of how TRIACS work was/is correct -- albeit simplified because, eg, it neglects band-gap losses.

The equations (3a) I use/d are also approximations, although the solutions to the equations are themselves exact within rounding error. (For complex systems, the solutions to the equations are often themselves approximation.)

These equations can be used to create a suite of solutions (linear, square-law, log dimmer curves etc). Depending on the purpose, each may or may not be "close enough".

((There are no straw men here. These are each -- including linear equal-step

-- legitimate solutions depending on the purpose. Sylvan wrote: "Marc supposedly did not say he wanted equal intensity step" ;-) You also wrote: I [sylvan] supposedly said I wanted log curve" -- which was the approximation closest to you stated qualitative description of human perception of light.))

But sylvan's/your Conceptual Model (2) of how TRIACS work was flat-out wrong.

And you were unable to provide mathematical descriptions as either waveforms or equations (3a & 4a See your non-responsive answers to Dan's simple questions.

And because your conceptual model (2) of how TRIACS work was incorrect, --> your Physical Model (3b) was _also_ incorrect (unsynchronized control of a TRIAC gate) --> your Physical Solution (4b) was _also_ incorrect (you could never create a non-flickering 50% of power, voltage, light output or anything else).

Although your 'Solutions' (4b) didn't actually didn't work, you had in mind what you wanted the results to look like and apparently believed that 'perceptual coding' in (3) was somehow going to fix the problem with you. It didn't, couldn't, and never can (except by chance) because the physics in the conceptual model are more fundamental than the conceptual model (See my previous comments to this effect.)

Actually, we've accomplished the main objective quite completely.

I have been persistent in countering your unproven claims that you can make a TRIAC dim evenly without synchronizing to the zero-crossing. That is now clear, with or without your cooperation, and hopefully others will not waste _their_ time attempting your futile approach. IOW, this is not about sylvan. It's about helping others.

Although you too presumably benefited: you could spend the rest of your life putzing with perceptual coding and *never* get the TRIACS to work with your approach. You did larn that, right? ;-)

That we might also benefit more from this overall discussion is part of the reason I spent time explaining my approach to things in the paragraphs above.

What I outlined above is one scientific approach, not a geologic, or hydrologic one. Physical modeling (your apparent approach under this organizational scheme) is neither more or less valid than mathematical modeling. Both needed to be checked (calibrated, validated, refined, choose your action/verb) with the Real World (1).

What is your field ( 'area of expertise', 'core competency') ?

I _do_ hope this helps ... Marc Marc_F_Hult

So you did in fact clearly and unambiguously "suggest[] creating a filtered 170vdc supply". It was this statement that I responded to. The record is crystal clear.

Can you peddle forwards as well as backwards?

... Marc Marc_F_hult

^^^^^^^^^^^^^^^ Should say: "because the physics in the Conceptual Model (2) are more fundamental to success than the particular Simulation Model (3) chosen"

...Marc Marc_F_Hult

Hmm... "Fundamentalist science!" Now there's a concept you won't hear very often. :^)

In forty years of designing electronic circuits, I've never seen the shorthand "ca." to mean "rectified but not filtered". But I suppose that is what you did mean. (I misunderstood you and yes, I can back peddle too ... ;-)

If one "[rectif[ies] the 120VAC to create ca. 170vdc and use MOSFETS", and don't also "filter" (add capacitance), you get 120Vrms which has a peak voltage of 170v with 100% ripple. And depending on how this is coupled and grounded (or not) it is either DC or AC. In this case, with respect to earth ground, it is DC sensu stricto (your point).

In the typical 120VAC circuit using MOSFETs for control of AC lamps, the lamps do see ~120VAC-(2 x 0.65)VAC -- not DC which is what I understood you to imply.

... Marc Marc_F_Hult

news: snipped-for-privacy@4ax.com...

Ouch! ;-)

You trying to 'get me going'? (We've been long-winded enough in these threads ...)

More seriously: Very glad to see you that you are maintaining good humor.

Get well ..Marc Marc_F_Hult

Thanks, Marc. I've been feeling progressively better the past few days. I even took my sweetheart out for a ride on my bike yesterday. We visited Venice Beach, enjoyed a meal on the pier watching all the snow birds play with their grand-kiddies in the sand. Life is great!

Next week I go in for my final chemo session. Then it will be two more weeks of misery before I'm finally done with this stuff. I'm planning a cross-country flight in a "Tiger" three weeks hence just to celebrate!

clearly and unambiguously "suggest"?? LOL.

Did not. :)

Indeed it is...

Forty years... So maybe you also started with vacuum tubes? I tried to convice the professor they were irrelevent, but he wouldn't hear it. Still have never used that since then...

"ca." means "circa" as in "approximately." As in, unless you know the exact A.C. peak voltage, and knowing that utility A.C. delivery tolerance is on the order of 10's of volts (RMS), and also not knowing the current vs Vf curve on the rectifier and of course not knowing the load, there really was no point is being any more precise than "approximately 170vdc."

Yes, we've seen how you continually suppose the worst.

Thank you, in the strictest sense.

sdb

According to your supposition of my model...

Simple question without a simple answer. A square wave is hard enough to describe mathmatically, but when it has varying on and off times, the math becomes more ugly than I care to deal with. It is easier to describe algorithmically, which I attempted.

Isn't it entertaining how much has been discovered "by chance" and practiced successfully for many years before the physics were understood and mathmatically described... Oh, wait, we are still trying to define many natural processes as we discover the previous formula did not describe the details visible under improved observation.

As I said, it'd probably be easier with the zero-crossing sync.

Professionally I guess you'd call me a software engineer or something like that, but that's only a few small facets.

I started playing with electricity before I could walk, computer stuff starting in 1976, and I've been online since 1982 when a friend working in a government lab created a gateway between his home BBS and the internet in his lab. I started college to get the sheep skin saying I knew electronics but found I liked the computer classes more. Now I have degrees in computer systems and computer science. Doing grounds maintenance and sprinkler system repair+installation plus a bit of warehouse management paid my way thru school (until I got my first software gig), so I graduated with good grades, a wife, no debt and money in the bank. And sometimes I think that was rather stupid, if I'd rented an expensive apartment and bought a new car I'd have qualified for government handouts to pay for it all... But oh well.

Non-professionally I've been known to do auto mechanics; home-related construction and repairs from framing on up including plumbing, electrical and HVAC; technical theatre; alternative energy systems (solar PV, thermal and wind); and yes, still the landscaping and a bit of electronics. I've never met a tool I didn't like. (All of my grandparents were college graduates, grandfathers were independent farmers who built their own homes and took care of everything themselves. I suppose I inherited a bit of that.)

Now I'm living on a hobby ranch with cows and chickens and four boys so I have also mucked out a stall and changed a diaper or two before the oldest learned how and when the misses wasn't available (she's a good one, let's me get away with a lot). I'm also a "Tech Plus" (too lazy to take the General and Am-Extra tests), and am NRA life (first member in my family) though I prefer GOA and JPFO (no I'm not Jewish).

Specialization is for insects. (from R.H. in his good days) The only problem is time to avoid it. But when I hire someone else it has always turned out no better than acceptable and usually worse. So I usually don't. Wondering if I should go into law or medicine next.

Still prefer to hire someone to do the butchering for me...

And all that is pretty much how I think of "me" at the moment.

Concluding thought for the day after elections: "That government is best which governs not at all." (Henry David Thoreau)

sdb

I am the OP and been following this post into the ground. Why reinvent the wheel, if not for just trying, its all been done before. Anyway I went with Light-O-Rama. The clincher was the new support for X10 devices witch I was all ready using so I can still use them for the slow stuff (1 min. or more) and the Light-O-Rama controllers for the fast stuff. The prices are reasonable. The program with coreographing for music is $100 and is well worth it. The controllers are cheep considering. The high power 16 channel Kit is $160, that's $10 per channel, as cheep as X10 but faster with more power. So for $300 I am on my way to dancing lights.

The posters that have kept this thread going have wasted more than that in there time and nothing was developed yet.

Thru out next year I will buy more kits and make more controllers until all

30,000 of my lights are on Light-O-Rama and I will not have to worry about the zero crossing optimum frequency of a random program.

Andy

Well said ;-)

(It should be apparent that the reason for my extending/participating in this discussion is to alert other folks that what Sylvan has proposed for controlling TRIACS simply will not work. Nor will his approach to using MOSFETs which I will explain as time permits. IOW, the intention has been to minimize the damage to the usefulness and credibility of information in comp.home.automation caused by sylvan's proposed electrical alchemy.)

+++++++++

I see no hint at

that the Light-O-Rama equipment is UL-listed. Perhaps I just missed it, but if it isn't, it wouldn't meet local code in many/most US jurisdictions. This may not pertain to your situation, but it could to many folks. It would be unfortunate to have a 30,000 light setup dimmed to dark.

... Marc Marc_F_Hult

wrote

message

yes Mark you are right about the lack of UL rating but most of these holiday light controllers are considered "hobbyist" like the kits I am buying.Plug them into professionally installed outlets and you are good to go. Andy