RE: [CAD_CAM_EDM_DRO] Re: Stepper Voltage and Current question

|I plan on limiting the current through transistors not resistors.
|This way when I pull 25 volts or 50 volts it will be limited to 2
|amps to the motor. I may also use FET's to keep the heat down. I just
|need to know if each winding is rated for 2 amps or is it divided
|between the 4. I was just curious performance wise how much voltage I
|needed. I may add a chopper cicuit by adding a 555 timer to the
|tranistor circuit but am working on the basic circuit first and try
|to make sure what I need voltage and current wise.

I think that you're forgetting that, for a unipolar motor, something has to
drop the voltage so the power supply can act as a current source. Whether
that something is a couple of power resistors or transistors, you still have
to dissipate the 100+ watts somewhere. Which means that unless you use the
transistor in a chopper design, you'll have to run it in its linear region.
When run in the linear region, it doesn't matter whether you use bipolar or
FET units, they still have to dissipate the POWER.

But to answer your question, each winding is most likely rated for 2 amps,
and you normally would have only two windings energized at any one time.

While you might be able to build a drive comparable to the Gecko drives for
half of the price, you'll waste far more money in burnt out components as
you perfect your design. (Read your comment above about using FET's instead
of resistors to keep the heat down and not realizing that they'll have to
dissipate the same heat).

Although you may think that Gecko drives are expensive at around $130 a pop,
I've used motor/drive combinations that cost about $2500 per axis. Compared
to those, the Geckos are a giveaway. If you're willing to build your own and
can get by with 2 amp units, look at Camtronics for something less
expensive. These are also bipolar drivers, and do not handle the same
current as the Geckos, but they may fit your application.

-- Jerry