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Date:	Fri, 21 May 1999 08:48:48 PDT
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: #5

Content Type: text/plain

> >I've got an N-scale double-8 track plan that I want OS/2 to control the
> >trains on.

> What's the power?

0-12 vdc. Some people control small DC motors at low speeds (when the
motor typically just stalls because the low voltage doesn't give it
enough "oomph" [technical term]) by pulsing a higher voltage, i.e.
instead of applying 1.0 volts you apply a 12.0 volt pulse about 10 times
per second. Because the winding is inductive and would thus keep the
higher frequency components of the pulse (ref: Fourier) from adding to
the power to the motor, I want to research the pulses and see if a sine
wave imposed over a DC component is just as effective. Some people
think the pulse is partially effective because the high-frequency spikes
spark through any oxidation on the rails or pickup wheels and allow the
remainder of the pulse to power the engine, so I might instead have to
impose a high-frequency AC component to do this. Anyway, it's not plain
old DC. In the studios we changed the speeds of phonograph record
players (we sometimes would speed up the records) by running a sinewave
signal generator into a speaker power amplifier, then taking the output
of the amplifier and running it backwards through a power supply
transformer to get 120 volts at not-quite-60 Hz. Worked great; The
Carpenters sounded _great_ when we cranked their tunes, though Neil
Diamond immediately got chipmunky so we had to leave him alone.

But you asked about power. Max is about 1.0 amp at 12.0 vdc.

> ... the train store on Sepulveda ...

That's a nice one, but I prefer the sightseer spots such as the Los
Angeles Live Steamers in Griffith Park (free rides every Sunday, as I
recall, and quite a large track layout with bridges, tunnels, freight
yards) and the various club model railroads (my favorite there is the
Sierra Pacific out in San Bernardino; the Pasadena Model Railroad Club
has a _huge_ layout; both have open houses several times a year).

Back on topic: The OS/2 control would need some one-bit input and
output for sensors and for control of gadgets, plus at least one D/A to
control the voltage to the rails. Simple parallel port stuff.

- Peter

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