Re: [CAD_CAM_EDM_DRO] Re: Driving unmarked steppers

> One might ask "what is a good current source" ? Well a good
> lab supply can do that but so can a norton equivalent... a battery and a
> resistor.

Nitpick, but a voltage source with a series resistor is the THEVENIN
equivelent of a current source with a shunt resistor, which is the
NORTON equivelent of the voltage source with series resistor.

A battery is neither a voltage source nor a current source - rather it
gets modeled as your choice of these equivelents with an internal
resistor. With a large resistor the approach isn't bad, but it's
probably good to use the meter across the source resistor to measure
the current. The problem though is that the resistor will probably
get pretty hot pretty quickly, which will change the resistance. A
few NiCd cells, a series ammeter, and a voltmeter across the coild
probably make a good test setup - simply add cells until you get a
reasonable current, then measure the voltage.

Chris Stratton

-------------------------------------------------
Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html