Re: MTH Proto-Sound 1 & Lionel ZW

Spender wrote:
On Sat, 28 Apr 2007 08:32:45 -0400, Wolf <ElLoboViejo@xxxxxxxxxx> wrote:

The AC current in your power line has a sine-wave shape (which you should recall from your high school math days.) A plain vanilla transformer produces lower voltage current of the same shape. The older Lionel transformers use a slider to cut more or less windings into the circuit, and so produce a variable voltage. Not very safe, actually, because you can fry the windings and cause a fire, but it works very well.

Is that why many (most?) of the old Lionel transformers could not receive
UL listing?

That, and the fact that a short circuit at 275 watts can generate a lot of heat in a very short time. Old timers talk of melting wheels...

Most modern power packs use solid state circuitry to turn off and on the current 120 time per second. The _average_ voltage is lower or higher, depending on the amount of time the current is off. So the speed of the locomotive is controlled. This chopping produces an instant voltage drop to zero, 120 times per second. If graphed, it looks like a shark fin. Why do it this way? Cost and safety.

120 times per second seems quite fast to my mind.

60 cycle current means from zero --> max plus --> zero --> min minus --> zero 60 times per second. That's two half waves per cycle. Each half wave is chopped by the electronics --> 120 chops per second.

But I guess it knocked
the circuitry of this loco for a loop. That might explain why if I
furiously fiddled with the throttle I could sometimes get it running. But
it still messed with the sound system since the horn would blow
continuously.

Cost as in less? I've read that the pure sine wave current transformers are
more expensive to produce. Might just be marketing hype, I don't know.

Transformers cost more because there contain a lot of copper and steel. Copper is high now - $3.51/lb USD!. High enough that thieves occasionally take down telephone cables, etc, for the copper in them. OTOH, solid state circuitry is made on large "wafers" which are cut up, so the cost per item is pennies.

BTW, thanks for this information. I'm inspired now to read up on the basics
of electronics.
[...]

You're welcome. I picked all my electrical/electronic knowledge by reading and doing, which expanded on and clarified the rather rudimentary stuff I learned in school. It's not difficult, if you take it one step at a time. I've even built a couple of transistorised controllers. Just follow the diagrams... ;-)

--


Wolf

"Don't believe everything you think." (Maxine)
.

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