On 2010-06-08, Karl Townsend wrote:

"Ignoramus8975" wrote in message
...
I am reading about AMC drives and how they are supposed to be
connected to tachometers for feedback.

And my question is, is this thing with brushes and wires a tachometer?

http://tinyurl.com/25zwke9

[ ... ]

you're looking at the motor brushes.

You don't use a tach with EMC.

That depends on the servo amplifiers. If you are using the
Gecko drivers for DC servos, then yes, the tach is not used. But the
Gecko is made to make the servo act like a stepper motor.

However -- other servo amps may well accept tach feedback.

Encoders go to control. Conrol sends -10v to
+10v to amps set in torque mode. Only connections on your amps are DC+ and
DC- in, Power+ and power- to servo, your analog reference signal and analog
ground. Also strongly recommend servo fault output and inhibit input if your
control will do these.

Which servo amps are you describing? It is not true of *all*
possible implementations of EMC. Many DC servo amps accept tach
feedback and automatically adjust the power to the servo motor so the
speed indicated by the tach feedback matches the speed commanded by the
control. I have similar SEM servo motors which do provide tach
feedback, and the AeroTech 4020 (+/-40V +/-20A) amplifiers which I have
utilize that tach feedback. You can command speeds which are slower
than the second hand on a clock with that -- even without the encoder
feedback. Just a servo amp, and a power supply which can output little
as a stable 0.001V or less.

Enjoy,
DoN.

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