Re: [CAD_CAM_EDM_DRO] Re: voltage based servo controller ?

Jon Elson wrote:

>Stephen Wille Padnos wrote:
>
>
>>You shouldn't need a "matching" motor. If you can find the current and
>>voltage limit, you can find a motor that it's capable of driving (just
>>like a gecko, but probably with different limits).
>>
>>
>>
>But, most velocity servo amps need a tachometer (or encoder->
>tach converter).
>
>

Yep - forgot to mention that you need *both* tach and position
feedback. Tach for the servo drive, position for the EMC2 motion
controller. If it's a torque mode drive, the feedback could be internal
(which eliminates the need for a tach), but I don't know if that was
common practice.

>>Sure. You can use EMC2 with PWM output on a parallel port pin (or other
>>supported I/O card). You'll need a little bit of filtering, a resistor
>>and capacitor should do it, though you may want to check your parport
>>output - it may not be symmetric (so it would take a bit of fiddling to
>>get the filter to decay at the same rate as it charges).
>>
>>
>This will almost work, but it will be unidirectional. You'd
>need additional circuitry (pretty simple, though) to flip the
>aritmetic sign of the analog output for the reverse direction.
>
>Jon
>
>

Right. I forgot about scaling as well. The PC output would be 0-5V (or
thereabouts), you'd need 0-10 in each direction.

It is just an op-amp circuit though, which isn't too difficult.

- Steve