Re: Speaking of cooked motors, "pulse power", etc.:
- From: "Bob May" <bobmay@xxxxxxxxxxx>
- Date: Tue, 11 Nov 2008 15:05:03 -0800
Basically, the idea of PWM is to use a switch to control the power with the
width of that switch on time being the percentage of the power desired to
the load.
Towards this end, the process is really quite simple. You take a source of
a sawtooth wave (the 555 timer chip does an excellent job of this in its
timing section) and then compare that against a voltage which you control.
The ouptut of the comparator goes to the switch. In the olden times, the
switch was usually a power transistor but the MOSFETs are a lot better at
this as they don't blow up when you abuse them as fast. In addition, there
is no high power requirement for a MASFET input to drive it on and off.
The nice thing is that the circuits don't need to have any heat sinks that
linear supplies have to have and thus a throttle can be put into even a
little 1"x1"x2" box without any trouble and still be able to control several
locos at a time.
--
Bob May
rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net
David Nebenzahl <nobody@xxxxxxxxxxxxxxx> wrote in message
news:491736e1$0$32366$822641b3@xxxxxxxxxxxxxxxxxxxxxxxxxxx
The previous thread on DC voltages, stalled motors and such has made me
curious about PWM (pulse-width modulation) for DC model train control.
Anyone have any schematics for a DIY PWM power supply? I did an
AltaVista search*, but couldn't find anything on the first try. Must be
several floating around out there. (Hello, Robert Heller?)
* I don't use Google; don't like their privacy intrusions, slanted
ranking system, etc. There are other search engines out there. If you
like Google's search results, you might consider using Scroogle instead
(Daniel Brandt's front end to Google that bypasses Google's
information-gathering functions): http://scroogle.org.
--
Washing one's hands of the conflict between the powerful and the
powerless means to side with the powerful, not to be neutral.
- Paulo Freire
.
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