Re: Controlling Holiday Lights

[sylvan butler <ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxxxxxxxx>]

On Mon, 06 Nov 2006 12:47:21 -0500, Marc_F_Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 06 Nov 2006 12:02:52 -0500, Marc_F_Hult
><MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote in message
><nkquk25nuvphhnqm9qj08mhu6hbuksamv1@xxxxxxx>:
>
>>On Sun, 5 Nov 2006 18:58:15 -0700, sylvan butler
>><ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>><slrnekt5ln.fbp.ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxx>:
>>
>>>On Fri, 03 Nov 2006 23:27:48 -0500, Marc_F_Hult
>><MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote:
>>>> On Fri, 3 Nov 2006 16:05:12 -0700, sylvan butler
>>>><ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxxxxxxxx> wrote in message
>>>><slrneknip8.p3a.ZsdbUse1+noZs_0611@xxxxxxxxxxxxxxx>:
>>>>>> would be doing is chopping the AC into really small chunks and they
>>>>>> would average over the entire wave(s).
>>>>>
>>>>>that's pretty much how it would work.  But it is a lot easier with D.C.
>>>>>You would have to be really motivated to do it with A.C.
>>>>
>>>> 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.
>>>
>>>You misunderstand.
>>>
>>>120vac sine wave == about +/-170v peak.  I was not suggesting creating a
>>>filtered 170vdc supply, just rectifying the 120vac sine wave.
>>
>>Of course you did. sylvan wrote:
>>
>>	"That gets a bit ugly (and more expensive) if you intend to
>>	control 120vac.  (Of course, one could rectify the 120vac to
>>	create ca. 170vdc and use MOSFETs...)
>>
>>So you did in fact clearly and unambiguously  "suggest[] creating a
>>filtered 170vdc supply".

clearly and unambiguously "suggest"??  LOL.

Did not.  :)


>> It was this statement that I responded to. The
>>record is crystal clear.

Indeed it is...


> In forty years of designing electronic circuits,

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...


> I've never seen the
> shorthand "ca." to mean "rectified but not filtered".

"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."

> But I suppose that is what you did mean.

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


> 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).

Thank you, in the strictest sense.

sdb

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