Re: Lowering Gecko Voltage

Hi,

Actually you can low-pass filter the output of the drive to run
nonstandard loads. This has been succesfully demonstrated for small,
low-inductance ironless armature motors like Maxon.

A 150 uH choke was placed in series with each motor lead and a non-
inductive 2 uF capacitor was placed across the motor. The low-pass
cutoff frequency was about 6 kHz, well below the 25 kHz switching of
the drive. Worked very well with those little motors.

Mariss

--- In CAD_CAM_EDM_DRO@y..., ccs@m... wrote:
>
> I really don't think this is a good way to do things at all.
>
> Piezo motors are high bandwidth capacitive loads. Electromagnetic
> motors are very low bandwidth inductive loads. The kinds of pulse
> width modulation approaches used to effeciently drive
electromagnetic
> motors are likely to fail horribly when applied to piezos - the
stack
> will try to wiggle at the PWM frame rate, and proportional control
of
> voltage will be nearly impossible, since the driver is only able to
> adjust the time average of current.
>
> This is really a job for op-amps. It is possible that you might be
> able to find a control signal inside a gecko drive which you could
use
> to run an op amp for driving the piezo... however that assumes
> that the gecko drive can keep up with your piezo stage, which it
> certainly could not do in the case of the small piezo elements I'm
use
> to working with.
>
> Chris Stratton
>
> -------------------------------------------------
> Christopher C. Stratton
> Engineer, Instrument Maker, and Horn Player
> ccs@m... 617 628 1062
> http://web.mit.edu/~stratton/www/brassbuild.html