Subject:
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Re: Electrical Things (was: Railroad Dilemma)
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Newsgroups:
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lugnet.trains
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Date:
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Mon, 8 Mar 1999 21:52:25 GMT
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Reply-To:
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{lpien@IWANTNOSPAM.}spamless{ctp.com}
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Viewed:
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5156 times
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Matthew Bates wrote:
>
> Simon Robinson writes:
> > If you have any URL's where people have reported on this, I'd be interested.
> So would I, because it's not true! As I've said this many times, it's plain
> and simple variable DC voltage with 6 steps. Look at...
>
> http://ourworld.compuserve.com/homepages/train_depot/current.htm
Your page says you used a voltmeter. That is insufficient evidence. Put
it on a scope.
If we have a PWM voltage with a 50% duty cycle and 10 millisecond period
An analog voltmeter will report the average voltage of 4.5, not 5
milliseconds DC 9V and 5 milliseconds DC 0V because it does not have the
timescale resolution to show that variation. The needle can't move that
fast. Now, I COULD be wrong, but I seem to remember someone reporting
that they did put it on a scope and saw PWM waveforms. Those are rather
striking as they look like square waves.
Put a DC voltmeter on an AC mains (don't try this at home, please, it's
a thought experiment) and you will see 0V. Yet the voltage is going to
110, back to 0, to -110V and back to 0 (RMS) 60 times a second.
While I did not pass electromagnetic fields :-), I DID have 4 years of
vocational electronics in high school and still remember a bit of it.
I will not argue whether this power supply uses PWM or not, as I said, I
don't recall exactly. But I will argue that an analog volt meter is
insufficient to determine if it does or not. So are all but the most
sophisticated digital meters.
--
Larry Pieniazek http://my.voyager.net/lar
Stop the FDIC from spying on us! Go to
http://www.defendyourprivacy.com and sign the petition.
For me: No voyager e-mail please. All snail-mail to Ada, please.
- Posting Binaries to RTL causes flamage... Don't do it, please.
- Stick to the facts when posting about others, please.
- This is a family newsgroup, thanks.
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Message has 1 Reply:
 | | Re: Electrical Things (was: Railroad Dilemma)
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| (...) interested. (...) True, I used a voltmeter to generate the data on that page, but I didn't claim anywhere on my page or previous posts that that was what I used to prove it is not PWM. Proof is obtained by opening the controller, getting the (...) (28 years ago, 8-Mar-99, to lugnet.trains)
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Message is in Reply To:
| | Re: Electrical Things (was: Railroad Dilemma)
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| (...) So would I, because it's not true! As I've said this many times, it's plain and simple variable DC voltage with 6 steps. Look at... (URL) (...) Also not true. The resistance of the motor is not enough to determine the current it will draw (...) (28 years ago, 8-Mar-99, to lugnet.trains)
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