Re: ATM DC motor speed control designs

["Bob May" <bobmay@nethere.com>]

If you are dealing with low voltage, go look up throttles for model trains
stuff.  The techniques can be used to the limits of the voltages and
currents of the parts used.  If your motor is a 90V one, it may be better to
use a switching type control rather than just dissapate the heat (which will
become quite considerable with the 90V) away.
If you are able to do some designing, some of the switching powersupply
chips can be used as nice regulators for a 90V supply - just use the
downconversion systems and you should be able to get a good range with a
variable feedback resistor.  FWIW, when doing any switching power supply you
do need to do very short paths on the high current stuff to keep the
parasitic resistances and impedances from affecting things.  Properly done,
a switching source can provide 80%+ efficiencies and thus little heat.  Most
designs have a current limit of some kind built in as a bonus.
Bob May
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Bob May