Re: [CAD_CAM_EDM_DRO] Re: Lowering Gecko Voltage

> Gary,
> How about series resistors on either side of the piezo motor, and
> maybe a R in parallel with the motor too. Say... run the Gecko at
> ~30vdc and use 3 5ohm 10Watt in series, with the motor in parallel
> with the center 5ohm R. ( might need to play with the R values.)
>
> You need to find out if the motor is usable with a PWM drive,
> otherwise you'll need to do some filtering to smooth the drive pulses
> to an averaging DC. Similar to what is done in a Class D amplifier.
>
> This piezo electric linear motor has an encoder connected to provide
> feedback? Thats req'd.

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@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html